Re: [PATCH v3 5/9] serial: qcom-geni: fix receiver enable

[Doug Anderson]

Hi,

On Wed, Oct 9, 2024 at 7:51 AM Johan Hovold <johan+linaro@xxxxxxxxxx> wrote:
>
> The receiver is supposed to be enabled in the startup() callback and not
> in set_termios() which is called also during console setup.
>
> This specifically avoids accepting input before the port has been opened
> (and interrupts enabled), something which can also break the GENI
> firmware (cancel fails and after abort, the "stale" counter handling
> appears to be broken so that later input is not processed until twelve
> chars have been received).
>
> There also does not appear to be any need to keep the receiver disabled
> while updating the port settings.
>
> Since commit 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during
> console writes") the calls to manipulate the secondary interrupts, which
> were done without holding the port lock, can also lead to the receiver
> being left disabled when set_termios() races with the console code (e.g.
> when init opens the tty during boot). This can manifest itself as a
> serial getty not accepting input.
>
> The calls to stop and start rx in set_termios() can similarly race with
> DMA completion and, for example, cause the DMA buffer to be unmapped
> twice or the mapping to be leaked.
>
> Fix this by only enabling the receiver during startup and while holding
> the port lock to avoid racing with the console code.
>
> Fixes: 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during console writes")
> Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA")
> Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP")
> Cc: stable@xxxxxxxxxxxxxxx      # 6.3
> Cc: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)

Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>