Re: [PATCH resend] Input: silead - Add workaround for x86 BIOS-es which bring the Silead chip up in a stuck state

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Mon, Apr 05, 2021 at 10:27:45PM +0200, Hans de Goede wrote:
> Some buggy BIOS-es bring up the touchscreen-controller in a stuck
> state where it blocks the I2C bus. Specifically this happens on
> the Jumper EZpad 7 tablet model.
> 
> After much poking at this problem I have found that the following steps
> are necessary to unstuck the chip / bus:
> 
> 1. Turn off the Silead chip.
> 2. Try to do an I2C transfer with the chip, this will fail in response to
>    which the I2C-bus-driver will call: i2c_recover_bus() which will unstuck
>    the I2C-bus. Note the unstuck-ing of the I2C bus only works if we first
>    drop the chip of the bus by turning it off.
> 3. Turn the chip back on.
> 
> On the x86/ACPI systems were this problem is seen, step 1. and 3. require
> making ACPI calls and dealing with ACPI Power Resources. This commit adds
> a workaround which runtime-suspends the chip to turn it off, leaving it up
> to the ACPI subsystem to deal with all the ACPI specific details.
> 
> There is no good way to detect this bug, so the workaround gets activated
> by a new "silead,stuck-controller-bug" boolean device-property. Since this
> is only used on x86/ACPI, this will be set by model specific device-props
> set by drivers/platform/x86/touchscreen_dmi.c. Therefor this new
> device-property is not documented in the DT-bindings.
> 
> Dmesg will contain the following messages on systems where the workaround
> is activated:
> 
> [   54.309029] silead_ts i2c-MSSL1680:00: [Firmware Bug]: Stuck I2C bus: please ignore the next 'controller timed out' error
> [   55.373593] i2c_designware 808622C1:04: controller timed out
> [   55.582186] silead_ts i2c-MSSL1680:00: Silead chip ID: 0x80360000
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Applied, thank you.

-- 
Dmitry