Re: [PATCH] drm/bridge: ti-sn65dsi86: Clear old error bits before AUX transfers

[Rob Clark <robdclark@gmail.com>]

On Fri, May 8, 2020 at 4:33 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> The AUX channel transfer error bits in the status register are latched
> and need to be cleared.  Clear them before doing our transfer so we
> don't see old bits and get confused.
>
> Without this patch having a single failure would mean that all future
> transfers would look like they failed.
>
> Fixes: b814ec6d4535 ("drm/bridge: ti-sn65dsi86: Implement AUX channel")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Rob Clark <robdclark@gmail.com>

> ---
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 6ad688b320ae..d865cc2565bc 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -827,6 +827,12 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
>                                      buf[i]);
>         }
>
> +       /* Clear old status bits before start so we don't get confused */
> +       regmap_write(pdata->regmap, SN_AUX_CMD_STATUS_REG,
> +                    AUX_IRQ_STATUS_NAT_I2C_FAIL |
> +                    AUX_IRQ_STATUS_AUX_RPLY_TOUT |
> +                    AUX_IRQ_STATUS_AUX_SHORT);
> +
>         regmap_write(pdata->regmap, SN_AUX_CMD_REG, request_val | AUX_CMD_SEND);
>
>         ret = regmap_read_poll_timeout(pdata->regmap, SN_AUX_CMD_REG, val,
> --
> 2.26.2.645.ge9eca65c58-goog
>
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