Re: [Intel-gfx] [PATCH 2/3] drm/dp: reuse the 8b/10b link training delay helpers

Ville Syrjälä
2021-10-14T15:43:37Z

On Thu, Oct 14, 2021 at 06:00:58PM +0300, Jani Nikula wrote:
> Reuse the 8b/10b link training delay helpers. Functionally this skips
> the check for invalid values for DPCD 1.4 and later at clock recovery
> delay (as it's a fixed delay and bypasses the rd_interval) but the same
> value will be checked and invalid values reported at channel
> equalization.
>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
> drivers/gpu/drm/drm_dp_helper.c | 30 ++++++++++--------------------
> 1 file changed, 10 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index f7ebf5974fa7..ada0a1ff262d 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -284,35 +284,25 @@ EXPORT_SYMBOL(drm_dp_read_channel_eq_delay);
> void drm_dp_link_train_clock_recovery_delay(const struct drm_dp_aux *aux,
> const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> {
> - unsigned long rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
> - DP_TRAINING_AUX_RD_MASK;
> + u8 rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
> + DP_TRAINING_AUX_RD_MASK;
> + int delay_us;
>
> - if (rd_interval > 4)
> - drm_dbg_kms(aux->drm_dev, "%s: AUX interval %lu, out of range (max 4)\n",
> - aux->name, rd_interval);
> -
> - if (rd_interval == 0 || dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
> - rd_interval = 100;
> + if (dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
> + delay_us = 100;
> else
> - rd_interval *= 4 * USEC_PER_MSEC;
> + delay_us = __8b10b_clock_recovery_delay_us(aux, rd_interval);
>
> - usleep_range(rd_interval, rd_interval * 2);
> + usleep_range(delay_us, delay_us * 2);
> }
> EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
>
> static void __drm_dp_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
> - unsigned long rd_interval)
> + u8 rd_interval)
> {
> - if (rd_interval > 4)
> - drm_dbg_kms(aux->drm_dev, "%s: AUX interval %lu, out of range (max 4)\n",
> - aux->name, rd_interval);
> -
> - if (rd_interval == 0)
> - rd_interval = 400;
> - else
> - rd_interval *= 4 * USEC_PER_MSEC;
> + int delay_us = __8b10b_channel_eq_delay_us(aux, rd_interval);
>
> - usleep_range(rd_interval, rd_interval * 2);
> + usleep_range(delay_us, delay_us * 2);
> }
>
> void drm_dp_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
> --
> 2.30.2

--
Ville Syrjälä
Intel