RE: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal Window watchdog mode
From: Srinivas Neeli
Date: Mon Oct 18 2021 - 05:23:50 EST
Hi Guenter,
Could you please share your comments on below limitations.
Thanks
Srinivas Neeli
> -----Original Message-----
> From: Srinivas Neeli <sneeli@xxxxxxxxxx>
> Sent: Wednesday, September 29, 2021 12:32 PM
> To: Guenter Roeck <linux@xxxxxxxxxxxx>; Shubhrajyoti Datta
> <shubhraj@xxxxxxxxxx>; Srinivas Goud <sgoud@xxxxxxxxxx>; Michal Simek
> <michals@xxxxxxxxxx>
> Cc: wim@xxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> Subject: RE: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal Window
> watchdog mode
>
> Hi Guenter,
>
> I went through reference "rti_wdt.c" driver. It implemented Window
> watchdog with few limitations.
> Limitations:
> ---------------
> 1) Not able to configure Closed window and Open window separately.
> Because of xilinx window watchdog supports separate configurable
> closed and open windows.
> 2) In case of rti driver, if any bad event(error event) occur due to any user
> space event like ping then
> the watchdog core bypassing the ping call.
> But in case of xilinx watchdog there are separate register bits for counting
> error events.
> So if I implement driver in similar to rti-wdt.c driver, then we can not
> be able read the error events from
> the registers.
> So is this ok because we are not notifying the errors to user.
>
> Thanks
> Srinivas Neeli
>
> > -----Original Message-----
> > From: Guenter Roeck <groeck7@xxxxxxxxx> On Behalf Of Guenter Roeck
> > Sent: Wednesday, July 14, 2021 5:01 PM
> > To: Srinivas Neeli <sneeli@xxxxxxxxxx>; Shubhrajyoti Datta
> > <shubhraj@xxxxxxxxxx>; Srinivas Goud <sgoud@xxxxxxxxxx>; Michal Simek
> > <michals@xxxxxxxxxx>
> > Cc: wim@xxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> > Subject: Re: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal Window
> > watchdog mode
> >
> > On 7/13/21 10:29 PM, Srinivas Neeli wrote:
> > > Hi Guenter,
> > >
> > > If you are fine with my justification, I will send v2 with update code.
> > >
> >
> > We have at least one more watchdog driver with open/closed window
> > concepts.
> > This is not a "pretimeout". Please see drivers/watchdog/rti_wdt.c for
> > an example on how to handle this; essentially you have to set
> > min_hw_heartbeat_ms to the value of the closed window timeout. The
> > watchdog core then handles the mechanics.
> >
> > You can not use "pretimeout" to set the "closed" window size; this is
> > an ABI abuse. There is no standard ABI for this, so if you want to
> > have it configurable it would have to be a module parameter.
> >
> > Guenter
> >
> > > Thanks
> > > Srinivas Neeli.
> > >
> > > *From:* Srinivas Neeli <sneeli@xxxxxxxxxx>
> > > *Sent:* Wednesday, June 9, 2021 12:57 PM
> > > *To:* Guenter Roeck <linux@xxxxxxxxxxxx>; Shubhrajyoti Datta
> > > <shubhraj@xxxxxxxxxx>; Srinivas Goud <sgoud@xxxxxxxxxx>; Michal
> > > Simek <michals@xxxxxxxxxx>
> > > *Cc:* wim@xxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx;
> > > linux-kernel@xxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> > > *Subject:* RE: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal Window
> > > watchdog mode
> > >
> > > Hi Guenter Roeck,
> > >
> > > Thanks for review.
> > >
> > > Versal platform contain System watchdog Timer. It supports two
> > > functions, Those are
> > >
> > > 1) Generic watchdog mode
> > >
> > > 2) Window watchdog mode
> > >
> > > Right now we are implementing window watchdog timer functionality in
> > driver.
> > >
> > > Features of Window watchdog mode:
> > >
> > > - The timer contains two configurable windows( closed and open).
> > >
> > > - The timer has to restart only in open window.
> > >
> > > - If software tries to restart out side of open window it will
> > > generate a
> > reset.
> > >
> > > We have a requirement for window watchdog driver, So I implemented
> > window watchdog in two scenarios.
> > >
> > > 1) With Pre-timeout
> > >
> > > 2) With without Pre-timeout
> > >
> > > *Scenario 1:*
> > >
> > > With pre-timeout:
> > >
> > > Here we will get two window concept.
> > >
> > > 1) closed window
> > >
> > > 2) Open window
> > >
> > > start to pre-timeout, we are calling "*closed*" window.
> > >
> > > From pre-timeout to timeout we are calling “*Open*” window.
> > >
> > > *Operations:*
> > >
> > > start
> > >
> > > keep alive(only in open window, closed window we are ignoring)
> > >
> > > stop
> > >
> > > we don't have permission to refresh/restart our timer in closed
> > > window, So
> > ignoring the keepalive.
> > >
> > > Adjusted code to generate interrupt after completion of closed window.
> > once we cross the closed window we can restart our time anytime.
> > >
> > > Once we reaches to timeout , will get reset signal.
> > >
> > > *Advantage:*
> > >
> > > After getting pre-timeout notification we can reset our timer or can
> > > collect
> > our log.
> > >
> > > once we get interrupt we can conclude our task is not working as
> expected.
> > >
> > > So we can takecare of our tasks.
> > >
> > > *Scenario 2:*
> > >
> > > with out pre-timeout:
> > >
> > > It will work like general watchdog timer.
> > >
> > > we can run keepalive anytime(as there is no closed window, only open
> > window present).
> > >
> > > Once we reaches to time out, will get reset.
> > >
> > > *Operations:*
> > >
> > > start
> > >
> > > keep alive
> > >
> > > stop
> > >
> > > For more details:
> > >
> > > https://www.xilinx.com/support/documentation/architecture-
> > manuals/am01
> > > 1-versal-acap-trm.pdf
> > > <https://www.xilinx.com/support/documentation/architecture-
> > manuals/am0
> > > 11-versal-acap-trm.pdf>
> > >
> > > major comments will update in V2.
> > >
> > > > -----Original Message-----
> > >
> > > > From: Guenter Roeck <groeck7@xxxxxxxxx
> > <mailto:groeck7@xxxxxxxxx>>
> > > On Behalf Of Guenter Roeck
> > >
> > > > Sent: Thursday, May 27, 2021 8:09 PM
> > >
> > > > To: Srinivas Neeli <sneeli@xxxxxxxxxx
> > > <mailto:sneeli@xxxxxxxxxx>>; Shubhrajyoti Datta
> > >
> > > > <shubhraj@xxxxxxxxxx <mailto:shubhraj@xxxxxxxxxx>>; Srinivas Goud
> > > <sgoud@xxxxxxxxxx <mailto:sgoud@xxxxxxxxxx>>; Michal Simek
> > >
> > > > <michals@xxxxxxxxxx <mailto:michals@xxxxxxxxxx>>
> > >
> > > > Cc: wim@xxxxxxxxxxxxxxxxxx <mailto:wim@xxxxxxxxxxxxxxxxxx>;
> > > linux-watchdog@xxxxxxxxxxxxxxx
> > > <mailto:linux-watchdog@xxxxxxxxxxxxxxx>; linux-
> > >
> > > > kernel@xxxxxxxxxxxxxxx <mailto:kernel@xxxxxxxxxxxxxxx>; git
> > > <git@xxxxxxxxxx <mailto:git@xxxxxxxxxx>>
> > >
> > > > Subject: Re: [PATCH 2/3] watchdog: xilinx_wwdt: Add Versal Window
> > >
> > > > watchdog mode
> > >
> > > >
> > >
> > > > The subject is confusing. This patch does not add "Versal Window
> > > watchdog
> > >
> > > > mode", it adds a driver which supports the Versal Window watchdog.
> > > The
> > >
> > > > subject should be something like "watchdog: Add Versal Window
> > > watchdog
> > >
> > > > driver".
> > >
> > > >
> > >
> > > > On 5/27/21 2:57 AM, Srinivas Neeli wrote:
> > >
> > > > > Versal watchdog driver uses Window watchdog mode. Window
> > watchdog
> > >
> > > > > timer(WWDT) contains closed(first) and open(second) window with
> > >
> > > > > 32 bit width. WWDT will generate an interrupt after the first
> > > window
> > >
> > > > > timeout and reset signal after the second window timeout.
> > > Timeout and
> > >
> > > > > Pre-timeout configuration, Stop and Refresh trigger only in
> > > open
> > >
> > > > > window.
> > >
> > > >
> > >
> > > > Does that mean that userspace can not send a keepalive before the
> > >
> > > > pretimeout expires ? That is not how this is supposed to work. If
> > > that is the
> > >
> > > > case, this is not a pretimeout. Pretimeout is supposed to be used
> > > for
> > >
> > > > emergency handling, such as triggering a crash dump. The above
> > > description
> > >
> > > > as well as the code suggests that an interrupt is all but mandatory.
> > >
> > > >
> > >
> > > > Assuming that is all the case, ie that keepalive is only possible
> > > after the
> > >
> > > > interrupt was received, and that timeout updates are also only
> > > possible after
> > >
> > > > an interrupt was received, one possible handling would to record
> > > that a
> > >
> > > > keepalive was received, and to record that a request to update
> > > the timeout
> > >
> > > > was received if that happens while the window is closed. Then,
> > > when the
> > >
> > > > interrupt is received, those actions can be applied. Otherwise,
> > > if there was
> > >
> > > > no keepalive request prior to the interrupt, the interrupt
> > > handler would call
> > >
> > > > watchdog_notify_pretimeout().
> > >
> > > >
> > >
> > > > Of course, this is all just guesswork.
> > >
> > > >
> > >
> > > > More comments below.
> > >
> > > >
> > >
> > > > Guenter
> > >
> > > >
> > >
> > > > >
> > >
> > > > > Signed-off-by: Srinivas Neeli <srinivas.neeli@xxxxxxxxxx
> > > <mailto:srinivas.neeli@xxxxxxxxxx>>
> > >
> > > > > ---
> > >
> > > > > drivers/watchdog/Kconfig | 16 ++
> > >
> > > > > drivers/watchdog/Makefile | 1 +
> > >
> > > > > drivers/watchdog/xilinx_wwdt.c | 382
> > >
> > > > +++++++++++++++++++++++++++++++++
> > >
> > > > > 3 files changed, 399 insertions(+)
> > >
> > > > > create mode 100644 drivers/watchdog/xilinx_wwdt.c
> > >
> > > > >
> > >
> > > > > diff --git a/drivers/watchdog/Kconfig
> > > b/drivers/watchdog/Kconfig index
> > >
> > > > > 355100dad60a..2ed17f278783 100644
> > >
> > > > > --- a/drivers/watchdog/Kconfig
> > >
> > > > > +++ b/drivers/watchdog/Kconfig
> > >
> > > > > @@ -307,6 +307,22 @@ config XILINX_WATCHDOG
> > >
> > > > > To compile this driver as a module, choose M here:
> > > the
> > >
> > > > > module will be called of_xilinx_wdt.
> > >
> > > > >
> > >
> > > > > +config XILINX_WINDOW_WATCHDOG
> > >
> > > > > + tristate "Xilinx Window Watchdog timer"
> > >
> > > > > + depends on HAS_IOMEM
> > >
> > > > > + select WATCHDOG_CORE
> > >
> > > > > + help
> > >
> > > > > + Window Watchdog driver for the versal_wwdt ip core.
> > >
> > > > > + Window watchdog timer(WWDT) contains closed(first) and
> > >
> > > > > + open(second) window with 32 bit width. WWDT will
> > > generate
> > >
> > > > > + an interrupt after the first window timeout and reset
> > >
> > > > > + signal after the second window timeout. Timeout and
> > >
> > > > > + Pre-timeout configuration, Stop and Refresh trigger
> > >
> > > > > + only in open window.
> > >
> > > > > +
> > >
> > > > > + To compile this driver as a module, choose M here: the
> > >
> > > > > + module will be called xilinx_wwdt.
> > >
> > > > > +
> > >
> > > > > config ZIIRAVE_WATCHDOG
> > >
> > > > > tristate "Zodiac RAVE Watchdog Timer"
> > >
> > > > > depends on I2C
> > >
> > > > > diff --git a/drivers/watchdog/Makefile
> > > b/drivers/watchdog/Makefile
> > >
> > > > > index a7eade8b4d45..97d10c3d39c7 100644
> > >
> > > > > --- a/drivers/watchdog/Makefile
> > >
> > > > > +++ b/drivers/watchdog/Makefile
> > >
> > > > > @@ -148,6 +148,7 @@ obj-$(CONFIG_M54xx_WATCHDOG) +=
> > >
> > > > m54xx_wdt.o
> > >
> > > > >
> > >
> > > > > # MicroBlaze Architecture
> > >
> > > > > obj-$(CONFIG_XILINX_WATCHDOG) += of_xilinx_wdt.o
> > >
> > > > > +obj-$(CONFIG_XILINX_WINDOW_WATCHDOG) += xilinx_wwdt.o
> > >
> > > > >
> > >
> > > > > # MIPS Architecture
> > >
> > > > > obj-$(CONFIG_ATH79_WDT) += ath79_wdt.o diff --git
> > >
> > > > > a/drivers/watchdog/xilinx_wwdt.c
> > > b/drivers/watchdog/xilinx_wwdt.c new
> > >
> > > > > file mode 100644 index 000000000000..8fa2cb2225e8
> > >
> > > > > --- /dev/null
> > >
> > > > > +++ b/drivers/watchdog/xilinx_wwdt.c
> > >
> > > > > @@ -0,0 +1,382 @@
> > >
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > >
> > > > > +/*
> > >
> > > > > + * Window Watchdog Device Driver for Xilinx Versal WWDT
> > >
> > > > > + *
> > >
> > > > > + * (C) Copyright 2021 Xilinx, Inc.
> > >
> > > > > + */
> > >
> > > > > +
> > >
> > > > > +#include <linux/clk.h>
> > >
> > > > > +#include <linux/interrupt.h>
> > >
> > > > > +#include <linux/io.h>
> > >
> > > > > +#include <linux/ioport.h>
> > >
> > > > > +#include <linux/of_device.h>
> > >
> > > > > +#include <linux/of_address.h>
> > >
> > > > > +#include <linux/module.h>
> > >
> > > > > +#include <linux/watchdog.h>
> > >
> > > > > +
> > >
> > > > > +#define XWWDT_DEFAULT_TIMEOUT 40
> > >
> > > > > +#define XWWDT_MIN_TIMEOUT 1
> > >
> > > > > +#define XWWDT_MAX_TIMEOUT 42
> > >
> > > > > +
> > >
> > > > > +/* Register offsets for the WWdt device */
> > >
> > > > > +#define XWWDT_MWR_OFFSET 0x00
> > >
> > > > > +#define XWWDT_ESR_OFFSET 0x04
> > >
> > > > > +#define XWWDT_FCR_OFFSET 0x08
> > >
> > > > > +#define XWWDT_FWR_OFFSET 0x0c
> > >
> > > > > +#define XWWDT_SWR_OFFSET 0x10
> > >
> > > > > +
> > >
> > > > > +/* Master Write Control Register Masks */
> > >
> > > > > +#define XWWDT_MWR_MASK BIT(0)
> > >
> > > > > +
> > >
> > > > > +/* Enable and Status Register Masks */
> > >
> > > > > +#define XWWDT_ESR_WINT_MASK BIT(16)
> > >
> > > > > +#define XWWDT_ESR_WSW_MASK BIT(8)
> > >
> > > > > +#define XWWDT_ESR_WEN_MASK BIT(0)
> > >
> > > > > +
> > >
> > > > > +/* Function control Register Masks */
> > >
> > > > > +#define XWWDT_SBC_MASK 0xFF00
> > >
> > > > > +#define XWWDT_SBC_SHIFT 16
> > >
> > > > > +#define XWWDT_BSS_MASK 0xC0
> > >
> > > > > +
> > >
> > > > > +static int wwdt_timeout;
> > >
> > > > > +
> > >
> > > > > +module_param(wwdt_timeout, int, 0644);
> > >
> > > > MODULE_PARM_DESC(wwdt_timeout,
> > >
> > > > > + "Watchdog time in seconds. (default="
> > >
> > > > > + __MODULE_STRING(XWWDT_DEFAULT_TIMEOUT)
> > > ")");
> > >
> > > > > +
> > >
> > > > > +struct xwwdt_device {
> > >
> > > > > + void __iomem *base;
> > >
> > > > > + spinlock_t spinlock; /* spinlock for register handling
> > > */
> > >
> > > > > + struct watchdog_device xilinx_wwdt_wdd;
> > >
> > > > > + struct clk *clk;
> > >
> > > > > + int irq;
> > >
> > > > > +};
> > >
> > > > > +
> > >
> > > > > +static int is_wwdt_in_closed_window(struct watchdog_device
> > > *wdd)
> > >
> > > >
> > >
> > > > should return bool
> > >
> > > Will update in V2.
> > >
> > > >
> > >
> > > > > +{
> > >
> > > > > + u32 control_status_reg;
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > +
> > >
> > > > > + spin_lock(&xdev->spinlock);
> > >
> > > > > + control_status_reg = ioread32(xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > + spin_unlock(&xdev->spinlock);
> > >
> > > > > + if (control_status_reg & XWWDT_ESR_WEN_MASK)
> > >
> > > > > + if (!(control_status_reg &
> > > XWWDT_ESR_WSW_MASK))
> > >
> > > > > + return 0;
> > >
> > > > > +
> > >
> > > > > + return 1;
> > >
> > > >
> > >
> > > > Can be written as expresion without if statement
> > >
> > > Will update in V2
> > >
> > > >
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static int xilinx_wwdt_start(struct watchdog_device *wdd) {
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > + struct watchdog_device *xilinx_wwdt_wdd = &xdev-
> > >
> > > > >xilinx_wwdt_wdd;
> > >
> > > > > + u64 time_out, pre_timeout, count;
> > >
> > > > > + u32 control_status_reg, fcr;
> > >
> > > > > + int ret;
> > >
> > > > > +
> > >
> > > > > + count = clk_get_rate(xdev->clk);
> > >
> > > > > + if (!count)
> > >
> > > > > + return -EINVAL;
> > >
> > > > > +
> > >
> > > > Is there a reason to believe that the clock rate can change ?
> > >
> > > > If not I would suggest to read it once and store it in struct
> xwwdt_device.
> > >
> > > Will update in V2.
> > >
> > > >
> > >
> > > > > + /* Calculate timeout count */
> > >
> > > > > + pre_timeout = count * wdd->pretimeout;
> > >
> > > > > + time_out = count * wdd->timeout;
> > >
> > > > > + if (!watchdog_active(xilinx_wwdt_wdd)) {
> > >
> > > > > + ret = clk_enable(xdev->clk);
> > >
> > > >
> > >
> > > > This is at the very least confusing.
> > >
> > > > The last action in the probe function is to call
> > > clk_disable_unprepare(),
> > >
> > > > meaning the clock should not be prepared here. How can it be
> > > enabled
> > >
> > > > without being prepared ?
> > >
> > > Will update in V2
> > >
> > > >
> > >
> > > > > + if (ret) {
> > >
> > > > > + dev_err(wdd->parent,
> > > "Failed to enable clock\n");
> > >
> > > > > + return ret;
> > >
> > > > > + }
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > I think it would be better to separate the functions to
> > > start/stop the clock
> > >
> > > > from the function to update/enable the watchdog. The use of
> > >
> > > > watchdog_active() combined with
> > >
> > > > clk_enable/clk_disable/clk_prepare_enable/clk_disable_unprepare
> > >
> > > > is confusing and makes it all but impossible to review the driver.
> > >
> > > >
> > >
> > > > > + spin_lock(&xdev->spinlock);
> > >
> > > > > + iowrite32(XWWDT_MWR_MASK, xdev->base +
> > >
> > > > XWWDT_MWR_OFFSET);
> > >
> > > > > + iowrite32(~(u32)XWWDT_ESR_WEN_MASK,
> > >
> > > > > + xdev->base + XWWDT_ESR_OFFSET);
> > >
> > > > > +
> > >
> > > > > + if (pre_timeout) {
> > >
> > > > > + iowrite32((u32)(time_out - pre_timeout),
> > >
> > > > > + xdev->base +
> > > XWWDT_FWR_OFFSET);
> > >
> > > > > + iowrite32((u32)pre_timeout, xdev->base +
> > >
> > > > XWWDT_SWR_OFFSET);
> > >
> > > > > + fcr = ioread32(xdev->base +
> > > XWWDT_SWR_OFFSET);
> > >
> > > > > + fcr = (fcr >> XWWDT_SBC_SHIFT) &
> > > XWWDT_SBC_MASK;
> > >
> > > > > + fcr = fcr | XWWDT_BSS_MASK;
> > >
> > > > > + iowrite32(fcr, xdev->base +
> > > XWWDT_FCR_OFFSET);
> > >
> > > > > + } else {
> > >
> > > > > + iowrite32((u32)pre_timeout,
> > >
> > > > > + xdev->base +
> > > XWWDT_FWR_OFFSET);
> > >
> > > > > + iowrite32((u32)time_out, xdev->base +
> > >
> > > > XWWDT_SWR_OFFSET);
> > >
> > > > > + iowrite32(0x0, xdev->base +
> > > XWWDT_FCR_OFFSET);
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + /* Enable the window watchdog timer */
> > >
> > > > > + control_status_reg = ioread32(xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > + control_status_reg |= XWWDT_ESR_WEN_MASK;
> > >
> > > > > + iowrite32(control_status_reg, xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > +
> > >
> > > > > + spin_unlock(&xdev->spinlock);
> > >
> > > > > +
> > >
> > > > > + dev_dbg(xilinx_wwdt_wdd->parent, "Watchdog Started!\n");
> > >
> > > > > +
> > >
> > > > > + return 0;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static int xilinx_wwdt_stop(struct watchdog_device *wdd) {
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > + struct watchdog_device *xilinx_wwdt_wdd = &xdev-
> > >
> > > > >xilinx_wwdt_wdd;
> > >
> > > > > +
> > >
> > > > > + if (!is_wwdt_in_closed_window(wdd)) {
> > >
> > > > > + dev_warn(xilinx_wwdt_wdd->parent, "timer
> > > in closed
> > >
> > > > window");
> > >
> > > > > + return -EINVAL;
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + spin_lock(&xdev->spinlock);
> > >
> > > > > +
> > >
> > > > > + iowrite32(XWWDT_MWR_MASK, xdev->base +
> > >
> > > > XWWDT_MWR_OFFSET);
> > >
> > > > > + /* Disable the Window watchdog timer */
> > >
> > > > > + iowrite32(~(u32)XWWDT_ESR_WEN_MASK,
> > >
> > > > > + xdev->base + XWWDT_ESR_OFFSET);
> > >
> > > > > +
> > >
> > > > > + spin_unlock(&xdev->spinlock);
> > >
> > > > > +
> > >
> > > > > + if (watchdog_active(xilinx_wwdt_wdd))
> > >
> > > > > + clk_disable(xdev->clk);
> > >
> > > > > +
> > >
> > > >
> > >
> > > > The stop function won't be called if the watchdog is not running,
> > > ie if
> > >
> > > > watchdog_active() returns false.
> > >
> > > > I don't undeerstand the logic of clock handling in this driver.
> > >
> > > > More on that below.
> > >
> > > >
> > >
> > > > > + dev_dbg(xilinx_wwdt_wdd->parent, "Watchdog Stopped!\n");
> > >
> > > > > +
> > >
> > > > > + return 0;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static int xilinx_wwdt_keepalive(struct watchdog_device *wdd)
> > > {
> > >
> > > > > + u32 control_status_reg;
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > +
> > >
> > > > > + /* Refresh in open window is ignored */
> > >
> > > > > + if (!is_wwdt_in_closed_window(wdd))
> > >
> > > > > + return 0;
> > >
> > > > > +
> > >
> > > > This is dangerous. There is no reason for userspace to adhere to
> > > these
> > >
> > > > restrictions.
> > >
> > > >
> > >
> > > > > + spin_lock(&xdev->spinlock);
> > >
> > > > > +
> > >
> > > > > + iowrite32(XWWDT_MWR_MASK, xdev->base +
> > >
> > > > XWWDT_MWR_OFFSET);
> > >
> > > > > + control_status_reg = ioread32(xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > + control_status_reg |= XWWDT_ESR_WINT_MASK;
> > >
> > > > > + control_status_reg &= ~XWWDT_ESR_WSW_MASK;
> > >
> > > > > + iowrite32(control_status_reg, xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > + control_status_reg = ioread32(xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > + control_status_reg |= XWWDT_ESR_WSW_MASK;
> > >
> > > > > + iowrite32(control_status_reg, xdev->base +
> > > XWWDT_ESR_OFFSET);
> > >
> > > > > +
> > >
> > > > > + spin_unlock(&xdev->spinlock);
> > >
> > > > > +
> > >
> > > > > + return 0;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static int xilinx_wwdt_set_timeout(struct watchdog_device
> > > *wdd,
> > >
> > > > > +
> > > unsigned int new_time)
> > >
> > > > > +{
> > >
> > > > > + u32 ret = 0;
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > + struct watchdog_device *xilinx_wwdt_wdd = &xdev-
> > >
> > > > >xilinx_wwdt_wdd;
> > >
> > > > > +
> > >
> > > > > + if (!is_wwdt_in_closed_window(wdd)) {
> > >
> > > > > + dev_warn(xilinx_wwdt_wdd->parent, "timer
> > > in closed
> > >
> > > > window");
> > >
> > > > > + return -EINVAL;
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > >
> > >
> > > > So userspace can clog the log by continuously trying to set the timeout
> ?
> > >
> > > >
> > >
> > > > Also, again, this is dangerous. Userspace does not know the window
> size.
> > >
> > > user can configure window size.
> > >
> > > >
> > >
> > > >
> > >
> > > > > + if (new_time < XWWDT_MIN_TIMEOUT ||
> > >
> > > > > + new_time > XWWDT_MAX_TIMEOUT) {
> > >
> > > > > + dev_warn(xilinx_wwdt_wdd->parent,
> > >
> > > > > + "timeout value must be
> > > %d<=x<=%d, using %d\n",
> > >
> > > > > + XWWDT_MIN_TIMEOUT,
> > >
> > > > > + XWWDT_MAX_TIMEOUT,
> > > new_time);
> > >
> > > > > + return -EINVAL;
> > >
> > > > > + }
> > >
> > > >
> > >
> > > > This is handled by the watchdog core.
> > >
> > > >
> > >
> > > > > +
> > >
> > > > > + wdd->timeout = new_time;
> > >
> > > > > + wdd->pretimeout = 0;
> > >
> > > > > +
> > >
> > > > > + if (watchdog_active(xilinx_wwdt_wdd)) {
> > >
> > > > > + ret = xilinx_wwdt_start(wdd);
> > >
> > > > > + if (ret)
> > >
> > > > > +
> > > dev_dbg(xilinx_wwdt_wdd->parent, "timer start
> > >
> > > > failed");
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + return ret;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static int xilinx_wwdt_set_pretimeout(struct watchdog_device
> > > *wdd,
> > >
> > > > > +
> > > u32
> > > new_pretimeout)
> > >
> > > > > +{
> > >
> > > > > + u32 ret = 0;
> > >
> > > > > + struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
> > >
> > > > > + struct watchdog_device *xilinx_wwdt_wdd = &xdev-
> > >
> > > > >xilinx_wwdt_wdd;
> > >
> > > > > +
> > >
> > > > > + if (!is_wwdt_in_closed_window(wdd)) {
> > >
> > > > > + dev_warn(xilinx_wwdt_wdd->parent, "timer
> > > in closed
> > >
> > > > window");
> > >
> > > > > + return -EINVAL;
> > >
> > > > > + }
> > >
> > > >
> > >
> > > > This restriction is not only dangerous but confusing, and simply
> > unacceptable.
> > >
> > > > Userspace will get -EINVAL with no idea what is wrong.
> > >
> > > > A watchdog daemon will bail out for no good reason.
> > >
> > > >
> > >
> > > > > +
> > >
> > > > > + if (new_pretimeout < wdd->min_timeout ||
> > >
> > > > > + new_pretimeout >= wdd->timeout)
> > >
> > > > > + return -EINVAL;
> > >
> > > > > +
> > >
> > > > This is handled by the watchdog core.
> > >
> > > >
> > >
> > > > > + wdd->pretimeout = new_pretimeout;
> > >
> > > > > +
> > >
> > > > > + if (watchdog_active(xilinx_wwdt_wdd)) {
> > >
> > > > > + ret = xilinx_wwdt_start(wdd);
> > >
> > > > > + if (ret)
> > >
> > > > > +
> > > dev_dbg(xilinx_wwdt_wdd->parent, "timer start
> > >
> > > > failed");
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + return ret;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static void xwwdt_clk_disable_unprepare(void *data) {
> > >
> > > > > + clk_disable_unprepare(data);
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static irqreturn_t xilinx_wwdt_isr(int irq, void *wdog_arg) {
> > >
> > > > > + struct xwwdt_device *xdev = wdog_arg;
> > >
> > > > > +
> > >
> > > > > + watchdog_notify_pretimeout(&xdev->xilinx_wwdt_wdd);
> > >
> > > > > +
> > >
> > > > > + return IRQ_HANDLED;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +static const struct watchdog_info xilinx_wwdt_ident = {
> > >
> > > > > + .options = WDIOF_MAGICCLOSE |
> > >
> > > > > + WDIOF_KEEPALIVEPING |
> > >
> > > > > + WDIOF_SETTIMEOUT,
> > >
> > > > > + .firmware_version = 1,
> > >
> > > > > + .identity = "xlnx_window watchdog",
> > >
> > > > > +};
> > >
> > > > > +
> > >
> > > > > +static const struct watchdog_info xilinx_wwdt_pretimeout_ident
> > > = {
> > >
> > > > > + .options = WDIOF_MAGICCLOSE |
> > >
> > > > > + WDIOF_KEEPALIVEPING |
> > >
> > > > > + WDIOF_PRETIMEOUT |
> > >
> > > > > + WDIOF_SETTIMEOUT,
> > >
> > > > > + .firmware_version = 1,
> > >
> > > > > + .identity = "xlnx_window watchdog",
> > >
> > > > > +};
> > >
> > > > > +
> > >
> > > > > +static const struct watchdog_ops xilinx_wwdt_ops = {
> > >
> > > > > + .owner = THIS_MODULE,
> > >
> > > > > + .start = xilinx_wwdt_start,
> > >
> > > > > + .stop = xilinx_wwdt_stop,
> > >
> > > > > + .ping = xilinx_wwdt_keepalive,
> > >
> > > > > + .set_timeout = xilinx_wwdt_set_timeout,
> > >
> > > > > + .set_pretimeout = xilinx_wwdt_set_pretimeout, };
> > >
> > > > > +
> > >
> > > > > +static int xwwdt_probe(struct platform_device *pdev) {
> > >
> > > > > + struct device *dev = &pdev->dev;
> > >
> > > > > + struct watchdog_device *xilinx_wwdt_wdd;
> > >
> > > > > + struct xwwdt_device *xdev;
> > >
> > > > > + u32 pre_timeout = 0;
> > >
> > > > > + int ret;
> > >
> > > > > +
> > >
> > > > > + xdev = devm_kzalloc(dev, sizeof(*xdev), GFP_KERNEL);
> > >
> > > > > + if (!xdev)
> > >
> > > > > + return -ENOMEM;
> > >
> > > > > +
> > >
> > > > > + xilinx_wwdt_wdd = &xdev->xilinx_wwdt_wdd;
> > >
> > > > > + xilinx_wwdt_wdd->info = &xilinx_wwdt_ident;
> > >
> > > > > + xilinx_wwdt_wdd->ops = &xilinx_wwdt_ops;
> > >
> > > > > + xilinx_wwdt_wdd->parent = dev;
> > >
> > > > > +
> > >
> > > > > + xdev->base = devm_platform_ioremap_resource(pdev, 0);
> > >
> > > > > + if (IS_ERR(xdev->base))
> > >
> > > > > + return PTR_ERR(xdev->base);
> > >
> > > > > +
> > >
> > > > > + ret = of_property_read_u32(dev->of_node,
> > > "pretimeout-sec",
> > >
> > > > > +
> > > &pre_timeout);
> > >
> > > > > + if (ret)
> > >
> > > > > + dev_dbg(dev,
> > >
> > > > > + "Parameter
> > > \"pretimeout-sec\" not found\n");
> > >
> > > > > +
> > >
> > > > > + xdev->clk = devm_clk_get(dev, NULL);
> > >
> > > > > + if (IS_ERR(xdev->clk))
> > >
> > > > > + return PTR_ERR(xdev->clk);
> > >
> > > > > +
> > >
> > > > > + ret = clk_get_rate(xdev->clk);
> > >
> > > > > + if (!ret)
> > >
> > > > > + return -EINVAL;
> > >
> > > > > +
> > >
> > > > > + ret = clk_prepare_enable(xdev->clk);
> > >
> > > > > + if (ret) {
> > >
> > > > > + dev_err(dev, "unable to enable
> > > clock\n");
> > >
> > > > > + return ret;
> > >
> > > > > + }
> > >
> > > > > + ret = devm_add_action_or_reset(dev,
> > >
> > > > xwwdt_clk_disable_unprepare,
> > >
> > > > > +
> > > xdev->clk);
> > >
> > > > > + if (ret)
> > >
> > > > > + goto err_clk_disable;
> > >
> > > > > +
> > >
> > > >
> > >
> > > > Seems pointless. What happens when you unload the driver ?
> > >
> > > >
> > >
> > > > > + xilinx_wwdt_wdd->pretimeout = pre_timeout;
> > >
> > > > > + xilinx_wwdt_wdd->timeout = XWWDT_DEFAULT_TIMEOUT;
> > >
> > > > > + xilinx_wwdt_wdd->min_timeout = XWWDT_MIN_TIMEOUT;
> > >
> > > > > + xilinx_wwdt_wdd->max_timeout = XWWDT_MAX_TIMEOUT;
> > >
> > > > > +
> > >
> > > > > + xdev->irq = platform_get_irq_byname(pdev, "wdt");
> > >
> > > > > + if (xdev->irq < 0) {
> > >
> > > > > + ret = xdev->irq;
> > >
> > > > > + goto err_clk_disable;
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + if (!devm_request_irq(dev, xdev->irq, xilinx_wwdt_isr,
> > >
> > > > > + 0, dev_name(dev),
> > > xdev)) {
> > >
> > > > > + xilinx_wwdt_wdd->info =
> > > &xilinx_wwdt_pretimeout_ident;
> > >
> > > > > + }
> > >
> > > > > +
> > >
> > > > > + ret = watchdog_init_timeout(xilinx_wwdt_wdd,
> > >
> > > > > +
> > > wwdt_timeout, &pdev->dev);
> > >
> > > > > + if (ret)
> > >
> > > > > + dev_info(&pdev->dev, "Configured default
> > > timeout
> > >
> > > > value\n");
> > >
> > > > > +
> > >
> > > > > + spin_lock_init(&xdev->spinlock);
> > >
> > > > > + watchdog_set_drvdata(xilinx_wwdt_wdd, xdev);
> > >
> > > > > +
> > >
> > > > > + ret = devm_watchdog_register_device(dev,
> > > xilinx_wwdt_wdd);
> > >
> > > > > + if (ret)
> > >
> > > > > + goto err_clk_disable;
> > >
> > > > > +
> > >
> > > > At this point the watchdog is fully instantiated, and userspace
> > > may have
> > >
> > > > enabled it.
> > >
> > > >
> > >
> > > > > + clk_disable_unprepare(xdev->clk);
> > >
> > > > > +
> > >
> > > > And now its clock is getting stopped. Actually, it is getting unprepared.
> > >
> > > > Does this even work ?
> > >
> > > >
> > >
> > > > > + dev_info(dev, "Xilinx Window Watchdog Timer with timeout
> > > %ds\n",
> > >
> > > > > + xilinx_wwdt_wdd->timeout);
> > >
> > > > > +
> > >
> > > > > + return 0;
> > >
> > > > > +
> > >
> > > > > +err_clk_disable:
> > >
> > > > > + clk_disable_unprepare(xdev->clk);
> > >
> > > >
> > >
> > > > devm_add_action_or_reset() already handles this.
> > >
> > > >
> > >
> > > > > + return ret;
> > >
> > > > > +}
> > >
> > > > > +
> > >
> > > > > +/* Mat for of_platform binding */
> > >
> > > > > +static const struct of_device_id xwwdt_of_match[] = {
> > >
> > > > > + { .compatible = "xlnx,versal-wwdt-1.0", },
> > >
> > > > > + {},
> > >
> > > > > +};
> > >
> > > > > +MODULE_DEVICE_TABLE(of, xwwdt_of_match);
> > >
> > > > > +
> > >
> > > > > +static struct platform_driver xwwdt_driver = {
> > >
> > > > > + .probe = xwwdt_probe,
> > >
> > > > > + .driver = {
> > >
> > > > > + .name = "Xilinx Window Watchdog",
> > >
> > > > > + .of_match_table = xwwdt_of_match,
> > >
> > > > > + },
> > >
> > > > > +};
> > >
> > > > > +
> > >
> > > > > +module_platform_driver(xwwdt_driver);
> > >
> > > > > +
> > >
> > > > > +MODULE_AUTHOR("Neeli Srinivas <sneeli@xxxxxxxxxx
> > > <mailto:sneeli@xxxxxxxxxx>>");
> > >
> > > > > +MODULE_DESCRIPTION("Xilinx Window Watchdog driver");
> > >
> > > > > +MODULE_LICENSE("GPL");
> > >
> > > > >
> > >
> > > Thanks
> > >
> > > Srinivas Neeli.
> > >