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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

Ugh, I had a local compile-fix which I forgot to git commit -a --amend,
so this version does not compile, please ignore.

V2 coming up right away.

Regards,

Hans



On 1/28/21 1:52 PM, 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>
> ---
>  drivers/input/touchscreen/silead.c | 39 +++++++++++++++++++++++++++---
>  1 file changed, 35 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/silead.c b/drivers/input/touchscreen/silead.c
> index 8fa2f3b7cfd8..9deef6317761 100644
> --- a/drivers/input/touchscreen/silead.c
> +++ b/drivers/input/touchscreen/silead.c
> @@ -20,6 +20,7 @@
>  #include <linux/input/mt.h>
>  #include <linux/input/touchscreen.h>
>  #include <linux/pm.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/irq.h>
>  #include <linux/regulator/consumer.h>
>  
> @@ -335,10 +336,8 @@ static int silead_ts_get_id(struct i2c_client *client)
>  
>  	error = i2c_smbus_read_i2c_block_data(client, SILEAD_REG_ID,
>  					      sizeof(chip_id), (u8 *)&chip_id);
> -	if (error < 0) {
> -		dev_err(&client->dev, "Chip ID read error %d\n", error);
> +	if (error < 0)
>  		return error;
> -	}
>  
>  	data->chip_id = le32_to_cpu(chip_id);
>  	dev_info(&client->dev, "Silead chip ID: 0x%8X", data->chip_id);
> @@ -351,12 +350,44 @@ static int silead_ts_setup(struct i2c_client *client)
>  	int error;
>  	u32 status;
>  
> +	/*
> +	 * Some buggy BIOS-es bring up the chip in a stuck state where it blocks the I2C bus.
> +	 * 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. The workaround below
> +	 * runtime-suspends the chip to turn it off, leaving it up to the ACPI subsystem
> +	 * to deal with this.
> +	 */
> +	if (device_property_read_bool(dev, "silead,stuck-controller-bug")) {
> +		pm_runtime_set_active(&client->dev);
> +		pm_runtime_enable(&client->dev);
> +		pm_runtime_allow(&client->dev);
> +
> +		pm_runtime_suspend(&client->dev);
> +
> +		dev_warn(&client->dev, FW_BUG "Stuck I2C bus: please ignore the next 'controller timed out' error\n");
> +		silead_ts_get_id(client);
> +
> +		/* The forbid will also resume the device */
> +		pm_runtime_forbid(&client->dev);
> +		pm_runtime_disable(&client->dev);
> +	}
> +
>  	silead_ts_set_power(client, SILEAD_POWER_OFF);
>  	silead_ts_set_power(client, SILEAD_POWER_ON);
>  
>  	error = silead_ts_get_id(client);
> -	if (error)
> +	if (error) {
> +		dev_err(&client->dev, "Chip ID read error %d\n", error);
>  		return error;
> +	}
>  
>  	error = silead_ts_init(client);
>  	if (error)
>