RE: [PATCH v3] TCO watchdog pretimeout handler

From: Muller, Francois-nicolas
Date: Thu Jun 18 2015 - 08:41:54 EST

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On Wed, June 17, 2015 6:06 PM, Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:

> On Wed, Jun 17, 2015 at 4:34 PM, Francois-Nicolas Muller <francois-nicolas.muller@xxxxxxxxx> wrote:
>
>> +#define DEFAULT_PRETIMEOUT 0
>> +static bool pretimeout = DEFAULT_PRETIMEOUT;
>
> Static variables should not be assigned to zero explicitly (it doesn't make sense).
> Moreover you have integer -> boolean implicit conversion.

Agree, I will remove the DEFAULT_PRETIMEOUT define.

> The below should go under CONFIG_ACPI.
>
>> +static unsigned char *tco_hid = "8086229C"; /* Intel Cherrytrail LPC
>> +*/

This codes also compiles with CONFIG_ACPI not defined, #if CONFIG_ACPI is not required here.

>> +static unsigned char *tco_hid = "8086229C"; /* Intel Cherrytrail LPC
>> +*/
>
> Why not to use acpi_device_id ?

As long as there is only one id, I think this is not required.
Anyway I will use acpi_device_id instead to be prepared for future ids.

>> + if (object.type != ACPI_TYPE_INTEGER)
>> + return AE_BAD_DATA;
>
> Do we really need this right now? Existing users of _GPE are considering the result as integer w/o an additional check.

Right, as this is already done elsewhere without the check, I will remove it.

Thanks,
Francois-Nicolas

-----Original Message-----
From: Andy Shevchenko [mailto:andy.shevchenko@xxxxxxxxx]
Sent: Wednesday, June 17, 2015 6:06 PM
To: Muller, Francois-nicolas
Cc: linux@xxxxxxxxxxxx; wim@xxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v3] TCO watchdog pretimeout handler

On Wed, Jun 17, 2015 at 4:34 PM, Francois-Nicolas Muller <francois-nicolas.muller@xxxxxxxxx> wrote:

First of all it would be nice to start a new thread per iteration.

> Use TCO watchdog first timeout (pretimeout) to dump CPU backtraces and
> ease debug of watchdog expiration causes.
> On Intel Cherrytrail, TCO logic generates a SMI, then SMI handler
> triggers a SCI to the kernel, on a specific GPE.
> The GPE handler dumps all CPU backtraces and calls panic (in order to
> execute registered panic callbacks).
> GPE number is configured from ACPI tables if LPC HID exists.
>
> Signed-off-by: Francois-Nicolas Muller
> <francois-nicolas.muller@xxxxxxxxx>
> ---
> SMI is not supported by the driver, only SCI.
>
> On Intel Cherrytrail, TCO watchdog raises an SMI, then the SMI handler
> in Bios trigs a SCI to the kernel (in Android OS configuration).
>
> The patch has some effect only on Cherrytrail platform.
> On Braswell, the TCO HID exists in ACPI tables, so SCI is configured.
> But the SMI handler does not trig the SCI.
> On other platforms, the HID does not exist in ACPI tables, and the SMI
> handler does not trig the SCI.
>
> In ACPI tables, _GPE is associated to this HID, so no possible confusion.
>
> FranÃois-Nicolas
> ---
> drivers/watchdog/iTCO_wdt.c | 50
> +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c
> index 3c3fd41..3e9ec8b 100644
> --- a/drivers/watchdog/iTCO_wdt.c
> +++ b/drivers/watchdog/iTCO_wdt.c
> @@ -68,6 +68,8 @@
> #include <linux/io.h> /* For inb/outb/... */
> #include <linux/mfd/core.h>
> #include <linux/mfd/lpc_ich.h>
> +#include <linux/nmi.h>
> +#include <linux/acpi.h>
>
> #include "iTCO_vendor.h"
>
> @@ -127,6 +129,12 @@ module_param(turn_SMI_watchdog_clear_off, int,
> 0); MODULE_PARM_DESC(turn_SMI_watchdog_clear_off,
> "Turn off SMI clearing watchdog (depends on
> TCO-version)(default=1)");
>
> +#define DEFAULT_PRETIMEOUT 0
> +static bool pretimeout = DEFAULT_PRETIMEOUT;

Static variables should not be assigned to zero explicitly (it doesn't make sense).
Moreover you have integer -> boolean implicit conversion.

> +module_param(pretimeout, bool, 0);
> +MODULE_PARM_DESC(pretimeout, "Enable watchdog pretimeout (default="
> + __MODULE_STRING(DEFAULT_PRETIMEOUT)
> +")");

Since it's boolean, I suppose to use direct value here. It would be one line.

> +
> /*
> * Some TCO specific functions
> */
> @@ -201,6 +209,45 @@ static int iTCO_wdt_unset_NO_REBOOT_bit(void)
> return ret; /* returns: 0 = OK, -EIO = Error */ }
>

The below should go under CONFIG_ACPI.

> +static unsigned char *tco_hid = "8086229C"; /* Intel Cherrytrail LPC
> +*/

Why not to use acpi_device_id ?

> +
> +static u32 iTCO_wdt_pretimeout_handler(acpi_handle gpe_device, u32 gpe,
> + void *context) {
> + /* dump backtraces for all available cores */
> + trigger_all_cpu_backtrace();
> +
> + /* call panic notifiers */
> + panic("Kernel Watchdog");
> +
> + return ACPI_INTERRUPT_HANDLED; }
> +
> +static acpi_status __init iTCO_wdt_register_gpe(acpi_handle handle,
> + u32 lvl, void *context, void
> +**rv) {
> + unsigned long long gpe;
> + acpi_status status;
> + union acpi_object object = { 0 };
> + struct acpi_buffer buffer = { sizeof(union acpi_object),
> +&object };
> +
> + status = acpi_evaluate_object(handle, "_GPE", NULL, &buffer);
> + if (ACPI_FAILURE(status))
> + return status;
> +
> + if (object.type != ACPI_TYPE_INTEGER)
> + return AE_BAD_DATA;

Do we really need this right now? Existing users of _GPE are considering the result as integer w/o an additional check.

> +
> + gpe = object.integer.value;
> + status = acpi_install_gpe_handler(NULL, gpe, ACPI_GPE_EDGE_TRIGGERED,
> + iTCO_wdt_pretimeout_handler,
> + NULL);

> + if (ACPI_FAILURE(status))
> + return status;
> +
> + acpi_enable_gpe(NULL, gpe);
> + return AE_OK;
> +}
> +
> static int iTCO_wdt_start(struct watchdog_device *wd_dev) {
> unsigned int val;
> @@ -641,6 +688,9 @@ static int __init iTCO_wdt_init_module(void)
> if (err)
> return err;
>
> + if (pretimeout)
> + acpi_get_devices(tco_hid, iTCO_wdt_register_gpe, NULL,
> + NULL);
> +
> return 0;
> }
>
> --
> 1.9.1
>
> --
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--
With Best Regards,
Andy Shevchenko
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Next message: Nicolas Ferre: "Re: [PATCH] clk: at91: add generated clock driver"
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