Re: [PATCH 3/7] drm/msm/dp: reset aux controller after dp_aux_cmd_fifo_tx() failed.

[Stephen Boyd <swboyd@chromium.org>]

Quoting Kuogee Hsieh (2021-07-06 10:20:16)
> Aux hardware calibration sequence requires resetting the aux controller
> in order for the new setting to take effect. However resetting the AUX
> controller will also clear HPD interrupt status which may accidentally
> cause pending unplug interrupt to get lost. Therefore reset aux
> controller only when link is in connection state when dp_aux_cmd_fifo_tx()
> fail. This fixes Link Layer CTS cases 4.2.1.1 and 4.2.1.2.
>
> Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_aux.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c
> index 4a3293b..eb40d84 100644
> --- a/drivers/gpu/drm/msm/dp/dp_aux.c
> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
> @@ -353,6 +353,9 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
>                         if (!(aux->retry_cnt % MAX_AUX_RETRIES))
>                                 dp_catalog_aux_update_cfg(aux->catalog);
>                 }
> +               /* reset aux if link is in connected state */
> +               if (dp_catalog_link_is_connected(aux->catalog))

How do we avoid resetting aux when hpd is unplugged and then plugged
back in during an aux transfer?

> +                       dp_catalog_aux_reset(aux->catalog);
>         } else {
>                 aux->retry_cnt = 0;
>                 switch (aux->aux_error_num) {
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>