On Fri, 9 Sept 2022 at 00:18, Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> wrote:
>
> Bring sink out of D3 (power down) mode into D0 (normal operation) mode
> by setting DP_SET_POWER_D0 bit to DP_SET_POWER dpcd register. This
> patch will retry 3 times if written to DP_SET_POWER register failed.
>
> Changes in v4:
> -- split into two patches
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/msm/dp/dp_link.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c
> index 36f0af0..7b5ecf5 100644
> --- a/drivers/gpu/drm/msm/dp/dp_link.c
> +++ b/drivers/gpu/drm/msm/dp/dp_link.c
> @@ -49,23 +49,26 @@ static int dp_aux_link_power_up(struct drm_dp_aux *aux,
> struct dp_link_info *link)
> {
> u8 value;
> - int err;
> + ssize_t len;
> + int i;
>
> if (link->revision < 0x11)
> return 0;
>
> - err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> - if (err < 0)
> - return err;
> + len = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> + if (len < 0)
> + return len;
This is a separate patch.
>
> value &= ~DP_SET_POWER_MASK;
> value |= DP_SET_POWER_D0;
>
> - err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> - if (err < 0)
> - return err;
> -
> - usleep_range(1000, 2000);
> + /* retry for 1ms to give the sink time to wake up */
> + for (i = 0; i < 3; i++) {
> + len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> + usleep_range(1000, 2000);
> + if (len == 1)
> + break;
> + }
>
> return 0;
> }
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
--
With best wishes
Dmitry
