Re: [PATCH] i2c: designware: platdrv: Remove DPM_FLAG_SMART_SUSPEND flag on BYT and CHT

[Wolfram Sang <wsa@the-dreams.de>]

[-- Attachment #1: Type: text/plain, Size: 3435 bytes --]

On Tue, Apr 07, 2020 at 08:11:16PM +0200, Hans de Goede wrote:
> We already set DPM_FLAG_SMART_PREPARE, so we completely skip all
> callbacks (other then prepare) where possible, quoting from
> dw_i2c_plat_prepare():
> 
>         /*
>          * If the ACPI companion device object is present for this device, it
>          * may be accessed during suspend and resume of other devices via I2C
>          * operation regions, so tell the PM core and middle layers to avoid
>          * skipping system suspend/resume callbacks for it in that case.
>          */
>         return !has_acpi_companion(dev);
> 
> Also setting the DPM_FLAG_SMART_SUSPEND will cause acpi_subsys_suspend()
> to leave the controller runtime-suspended even if dw_i2c_plat_prepare()
> returned 0.
> 
> Leaving the controller runtime-suspended normally, when the I2C controller
> is suspended during the suspend_late phase, is not an issue because
> the pm_runtime_get_sync() done by i2c_dw_xfer() will (runtime-)resume it.
> 
> But for dw I2C controllers on Bay- and Cherry-Trail devices acpi_lpss.c
> leaves the controller alive until the suspend_noirq phase, because it may
> be used by the _PS3 ACPI methods of PCI devices and PCI devices are left
> powered on until the suspend_noirq phase.
> 
> Between the suspend_late and resume_early phases runtime-pm is disabled.
> So for any ACPI I2C OPRegion accesses done after the suspend_late phase,
> the pm_runtime_get_sync() done by i2c_dw_xfer() is a no-op and the
> controller is left runtime-suspended.
> 
> i2c_dw_xfer() has a check to catch this condition (rather then waiting
> for the I2C transfer to timeout because the controller is suspended).
> acpi_subsys_suspend() leaving the controller runtime-suspended in
> combination with an ACPI I2C OPRegion access done after the suspend_late
> phase triggers this check, leading to the following error being logged
> on a Bay Trail based Lenovo Thinkpad 8 tablet:
> 
> [   93.275882] i2c_designware 80860F41:00: Transfer while suspended
> [   93.275993] WARNING: CPU: 0 PID: 412 at drivers/i2c/busses/i2c-designware-master.c:429 i2c_dw_xfer+0x239/0x280
> ...
> [   93.276252] Workqueue: kacpi_notify acpi_os_execute_deferred
> [   93.276267] RIP: 0010:i2c_dw_xfer+0x239/0x280
> ...
> [   93.276340] Call Trace:
> [   93.276366]  __i2c_transfer+0x121/0x520
> [   93.276379]  i2c_transfer+0x4c/0x100
> [   93.276392]  i2c_acpi_space_handler+0x219/0x510
> [   93.276408]  ? up+0x40/0x60
> [   93.276419]  ? i2c_acpi_notify+0x130/0x130
> [   93.276433]  acpi_ev_address_space_dispatch+0x1e1/0x252
> ...
> 
> So since on BYT and CHT platforms we want ACPI I2c OPRegion accesses
> to work until the suspend_noirq phase, we need the controller to be
> runtime-resumed during the suspend phase if it is runtime-suspended
> suspended at that time. This means that we must not set the
> DPM_FLAG_SMART_SUSPEND on these platforms.
> 
> On BYT and CHT we already have a special ACCESS_NO_IRQ_SUSPEND flag
> to make sure the controller stays functional until the suspend_noirq
> phase. This commit makes the driver not set the DPM_FLAG_SMART_SUSPEND
> flag when that flag is set.
> 
> Cc: stable@vger.kernel.org
> Fixes: b30f2f65568f ("i2c: designware: Set IRQF_NO_SUSPEND flag for all BYT and CHT controllers")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Applied to for-current, thanks!


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]