linux-kernel - Re: [PATCH v4 0/4] platform/x86: intel_scu

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Date:   Mon, 18 Sep 2023 15:15:47 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Stephen Boyd <swboyd@...omium.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Mark Gross <markgross@...nel.org>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        platform-driver-x86@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Prashant Malani <pmalani@...omium.org>
Subject: Re: [PATCH v4 0/4] platform/x86: intel_scu_ipc: Timeout fixes

Hi,

On 9/13/23 23:27, Stephen Boyd wrote:
> I recently looked at some crash reports on ChromeOS devices that call
> into this intel_scu_ipc driver. They were hitting timeouts, and it
> certainly looks possible for those timeouts to be triggering because of
> scheduling issues. Once things started going south, the timeouts kept
> coming. Maybe that's because the other side got seriously confused? I
> don't know.
> 
> I added some sleeps to these paths to trigger the timeout behavior to
> make sure the code works. Simply sleeping for a long time in busy_loop()
> hits the timeout, which could happen if the system is scheduling lots of
> other things at the time.
> 
> I couldn't really test the last patch because forcing a timeout or
> returning immediately wasn't fast enough to trigger the second
> transaction to run into the first one being processed.

Thank you for your patch, I've applied this patch to my fixes
branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=fixes

Note it will show up in my fixes branch once I've pushed my
local branch there, which might take a while.

I will include this patch in my next fixes pull-req to Linus
for the current kernel development cycle.

Regards,

Hans




> Changes from v3 (https://lore.kernel.org/r/20230911193937.302552-1-swboyd@chromium.org):
>  * Use readx_poll_timeout() to shorten a line
> 
> Changes from v2 (https://lore.kernel.org/r/20230906180944.2197111-1-swboyd@chromium.org):
>  * Use read_poll_timeout() helper in patch #1 (again)
>  * New patch #3 to fix bug pointed out by Andy
>  * Consolidate more code into busy check in patch #4
> 
> Changes from v1 (https://lore.kernel.org/r/20230831011405.3246849-1-swboyd@chromium.org):
>  * Don't use read_poll_timeout() helper in patch 1, just add code
>  * Rewrite patch 2 to be simpler
>  * Make intel_scu_ipc_busy() return -EBUSY when busy
>  * Downgrade dev_err() to dev_dbg() in intel_scu_ipc_busy()
> 
> Stephen Boyd (4):
>   platform/x86: intel_scu_ipc: Check status after timeout in busy_loop()
>   platform/x86: intel_scu_ipc: Check status upon timeout in
>     ipc_wait_for_interrupt()
>   platform/x86: intel_scu_ipc: Don't override scu in
>     intel_scu_ipc_dev_simple_command()
>   platform/x86: intel_scu_ipc: Fail IPC send if still busy
> 
>  drivers/platform/x86/intel_scu_ipc.c | 66 +++++++++++++++++-----------
>  1 file changed, 40 insertions(+), 26 deletions(-)
> 
> Cc: Prashant Malani <pmalani@...omium.org>
> 
> base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c