On Thu, Nov 24, 2022 at 11:53 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> On an Advantech MICA-071 tablet, with a builtin barcode scanner connected
> to ttyS0, the following message is shown on suspend:
>
> serial 00:02: disabled
>
> And after suspend/resume trying to use the barcode scanner / ttyS0 shows:
>
> serial 00:02: LSR safety check engaged!
>
> Indicating that the UARTs io-ports are no longer reachable.
>
> This is caused by __pnp_bus_suspend() calling pnp_stop_dev() on the "00:02"
> pnp device on suspend (this outputs the disabled message).
>
> The problem is that pnp_can_write() returns false for the "00:02" pnp
> device, so after disabling it (disabling its decoding of IO addresses)
> during suspend, it cannot be re-enabled.
>
> Add a pnp_can_write() check to the suspend path and only disable devices
> which can actually be re-enabled on resume.
>
> This fixes the Advantech MICA-071's ttyS0 no longer working after
> a suspend/resume.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> drivers/pnp/driver.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pnp/driver.c b/drivers/pnp/driver.c
> index c02e7bf643a6..46c534f6b1c9 100644
> --- a/drivers/pnp/driver.c
> +++ b/drivers/pnp/driver.c
> @@ -182,7 +182,8 @@ static int __pnp_bus_suspend(struct device *dev, pm_message_t state)
> return error;
> }
>
> - if (pnp_can_disable(pnp_dev)) {
> + /* can_write is necessary to be able to re-start the device on resume */
> + if (pnp_can_disable(pnp_dev) && pnp_can_write(pnp_dev)) {
> error = pnp_stop_dev(pnp_dev);
> if (error)
> return error;
> --
Applied as 6.2 material, thanks!
