Re: [PATCH v6] vfio: platform: reset: Add Broadcom FlexRM reset module

[Alex Williamson]

On Mon, 4 Sep 2017 15:20:11 +0530
Anup Patel <anup.patel@xxxxxxxxxxxx> wrote:

> Sorry for delayed response...
> 
> On Tue, Aug 29, 2017 at 7:39 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx> wrote:
> > On Tue, Aug 29, 2017 at 09:34:46AM +0530, Anup Patel wrote:  
> >> This patch adds Broadcom FlexRM low-level reset for
> >> VFIO platform.
> >>  
> >
> > Is there an document that explains and /or details the various
> > registers?  
> 
> Yes, there is a document but its not publicly accessible.
> 
> >> It will do the following:
> >> 1. Disable/Deactivate each FlexRM ring
> >> 2. Flush each FlexRM ring
> >>
> >> The cleanup sequence for FlexRM rings is adapted from
> >> Broadcom FlexRM mailbox driver.
> >>
> >> Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxx>
> >> Reviewed-by: Oza Oza <oza.oza@xxxxxxxxxxxx>
> >> Reviewed-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
> >> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> >> ---
> >>  drivers/vfio/platform/reset/Kconfig                |   9 ++
> >>  drivers/vfio/platform/reset/Makefile               |   1 +
> >>  .../vfio/platform/reset/vfio_platform_bcmflexrm.c  | 100 +++++++++++++++++++++
> >>  3 files changed, 110 insertions(+)
> >>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
> >>
> >> diff --git a/drivers/vfio/platform/reset/Kconfig b/drivers/vfio/platform/reset/Kconfig
> >> index 70cccc5..392e3c0 100644
> >> --- a/drivers/vfio/platform/reset/Kconfig
> >> +++ b/drivers/vfio/platform/reset/Kconfig
> >> @@ -13,3 +13,12 @@ config VFIO_PLATFORM_AMDXGBE_RESET
> >>         Enables the VFIO platform driver to handle reset for AMD XGBE
> >>
> >>         If you don't know what to do here, say N.
> >> +
> >> +config VFIO_PLATFORM_BCMFLEXRM_RESET
> >> +     tristate "VFIO support for Broadcom FlexRM reset"
> >> +     depends on VFIO_PLATFORM && (ARCH_BCM_IPROC || COMPILE_TEST)
> >> +     default ARCH_BCM_IPROC
> >> +     help
> >> +       Enables the VFIO platform driver to handle reset for Broadcom FlexRM
> >> +
> >> +       If you don't know what to do here, say N.
> >> diff --git a/drivers/vfio/platform/reset/Makefile b/drivers/vfio/platform/reset/Makefile
> >> index 93f4e23..8d9874b 100644
> >> --- a/drivers/vfio/platform/reset/Makefile
> >> +++ b/drivers/vfio/platform/reset/Makefile
> >> @@ -5,3 +5,4 @@ ccflags-y += -Idrivers/vfio/platform
> >>
> >>  obj-$(CONFIG_VFIO_PLATFORM_CALXEDAXGMAC_RESET) += vfio-platform-calxedaxgmac.o
> >>  obj-$(CONFIG_VFIO_PLATFORM_AMDXGBE_RESET) += vfio-platform-amdxgbe.o
> >> +obj-$(CONFIG_VFIO_PLATFORM_BCMFLEXRM_RESET) += vfio_platform_bcmflexrm.o
> >> diff --git a/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
> >> new file mode 100644
> >> index 0000000..966a813
> >> --- /dev/null
> >> +++ b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
> >> @@ -0,0 +1,100 @@
> >> +/*
> >> + * Copyright (C) 2017 Broadcom
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + *
> >> + * This program is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >> + * GNU General Public License for more details.
> >> + *
> >> + * You should have received a copy of the GNU General Public License
> >> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> >> + */
> >> +
> >> +/*
> >> + * This driver provides reset support for Broadcom FlexRM ring manager
> >> + * to VFIO platform.
> >> + */
> >> +
> >> +#include <linux/delay.h>
> >> +#include <linux/init.h>
> >> +#include <linux/io.h>
> >> +#include <linux/kernel.h>
> >> +#include <linux/module.h>
> >> +
> >> +#include "vfio_platform_private.h"
> >> +
> >> +/* FlexRM configuration */
> >> +#define RING_REGS_SIZE                                       0x10000
> >> +#define RING_VER_MAGIC                                       0x76303031
> >> +
> >> +/* Per-Ring register offsets */
> >> +#define RING_VER                                     0x000
> >> +#define RING_CONTROL                                 0x034
> >> +#define RING_FLUSH_DONE                                      0x038
> >> +
> >> +/* Register RING_CONTROL fields */
> >> +#define CONTROL_FLUSH_SHIFT                          5
> >> +
> >> +/* Register RING_FLUSH_DONE fields */
> >> +#define FLUSH_DONE_MASK                                      0x1
> >> +
> >> +static int vfio_platform_bcmflexrm_shutdown(void __iomem *ring)
> >> +{
> >> +     unsigned int timeout;
> >> +
> >> +     /* Disable/inactivate ring */
> >> +     writel_relaxed(0x0, ring + RING_CONTROL);
> >> +
> >> +     /* Flush ring with timeout of 1s */
> >> +     timeout = 1000;  
> >
> > Perhaps a #define for this value?  
> 
> This magic value 1000 makes it explicit that we try till 1 second
> because inside the loop we have mdelay(1).
> 
> >  
> >> +     writel_relaxed(BIT(CONTROL_FLUSH_SHIFT), ring + RING_CONTROL);
> >> +     do {
> >> +             if (readl_relaxed(ring + RING_FLUSH_DONE) & FLUSH_DONE_MASK)
> >> +                     break;
> >> +             mdelay(1);
> >> +     } while (--timeout);
> >> +
> >> +     if (!timeout) {
> >> +             pr_warn("VFIO FlexRM shutdown timeout\n");

Since you're planning a new version anyway, perhaps we could also pass
the device through and use a dev_warn here so we can associate this
error to a specific device.  Perhaps even knowing which ring on the
device encountered the timeout would be useful.  Thanks,

Alex

> >> +             return -ETIMEDOUT;
> >> +     }
> >> +
> >> +     return 0;
> >> +}  
> 
> There is a correction in the sequence suggested by HW folks.
> 
> After above, we need to clear the FLUSH bit in RING_CONTROL
> register and then wait for FLUSH_DONE bit to be cleared in
> RING_FLUSH_DONE register.
> 
> This was missed out previously due to incomplete documentation.
> 
> >> +
> >> +static int vfio_platform_bcmflexrm_reset(struct vfio_platform_device *vdev)
> >> +{
> >> +     int rc = 0;
> >> +     void __iomem *ring;
> >> +     struct vfio_platform_region *reg = &vdev->regions[0];
> >> +
> >> +     /* Map FlexRM ring registers if not mapped */
> >> +     if (!reg->ioaddr) {
> >> +             reg->ioaddr = ioremap_nocache(reg->addr, reg->size);
> >> +             if (!reg->ioaddr)
> >> +                     return -ENOMEM;
> >> +     }
> >> +
> >> +     /* Discover and shutdown each FlexRM ring */
> >> +     for (ring = reg->ioaddr;
> >> +          ring < (reg->ioaddr + reg->size); ring += RING_REGS_SIZE) {
> >> +             if (readl_relaxed(ring + RING_VER) == RING_VER_MAGIC) {
> >> +                     rc = vfio_platform_bcmflexrm_shutdown(ring);
> >> +                     if (rc)
> >> +                             break;  
> >
> > You sure? Don't you want to continue trying to reset all of them and
> > then return rc at the end?  
> 
> Yes, I think its better to reset all even if few fail. I will update this
> accordingly.
> 
> Thanks,
> Anup