On Mon, 23 Sep 2024, Chaitanya Kumar Borah <chaitanya.kumar.borah@xxxxxxxxx> wrote:
> From PTL, FEC_DECODE_EN sequence can be sent to a DPRX independent
> of TRANS_CONF enable. This allows us to re-issue an FEC_DECODE_EN
> sequence without re-doing the whole mode set sequence. This separate
> control over FEC_ECODE_EN/DIS sequence enables us to have a retry
> mechanism in case the DPRX does not respond with an FEC_ENABLE
> within the stipulated 5ms.
>
> Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_ddi.c | 61 +++++++++++++++++++++++-
> 1 file changed, 59 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 85e519a21542..589acea9906a 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -78,6 +78,8 @@
> #include "skl_scaler.h"
> #include "skl_universal_plane.h"
>
> +#define FEC_RETRY_COUNT 3
If there's only one user, I wouldn't bother with a macro.
> +
> static const u8 index_to_dp_signal_levels[] = {
> [0] = DP_TRAIN_VOLTAGE_SWING_LEVEL_0 | DP_TRAIN_PRE_EMPH_LEVEL_0,
> [1] = DP_TRAIN_VOLTAGE_SWING_LEVEL_0 | DP_TRAIN_PRE_EMPH_LEVEL_1,
> @@ -2255,6 +2257,57 @@ static int read_fec_detected_status(struct drm_dp_aux *aux)
> return status;
> }
>
> +static void retry_fec_enable(struct intel_encoder *encoder,
> + const struct intel_crtc_state *crtc_state,
> + struct drm_dp_aux *aux)
> +{
> + struct drm_i915_private *i915 = to_i915(aux->drm_dev);
> + int ret = 0;
> +
> + /* Clear FEC enable */
> + intel_de_rmw(i915, dp_tp_ctl_reg(encoder, crtc_state),
> + DP_TP_CTL_FEC_ENABLE, 0);
> +
> + /* Set FEC enable */
> + intel_de_rmw(i915, dp_tp_ctl_reg(encoder, crtc_state),
> + 0, DP_TP_CTL_FEC_ENABLE);
> +
> + ret = intel_de_wait_for_set(i915, dp_tp_status_reg(encoder, crtc_state),
> + DP_TP_STATUS_FEC_ENABLE_LIVE, 1);
> + if (!ret)
> + drm_dbg_kms(&i915->drm,
> + "Timeout waiting for FEC live state to get enabled");
> +}
> +
> +static void wait_for_fec_detected_with_retry(struct intel_encoder *encoder,
> + const struct intel_crtc_state *crtc_state,
> + struct drm_dp_aux *aux)
> +{
> + struct drm_i915_private *i915 = to_i915(aux->drm_dev);
> + int status;
> + int err;
> + int retrycount = 0;
> +
> + do {
> + err = readx_poll_timeout(read_fec_detected_status, aux, status,
> + status & DP_FEC_DECODE_EN_DETECTED || status < 0,
> + 500, 5000);
> +
> + if (!err && status >= 0)
> + return;
> +
> + if (err == -ETIMEDOUT) {
> + drm_dbg_kms(&i915->drm,
> + "Timeout waiting for FEC ENABLE to get detected, retrying\n");
> + retry_fec_enable(encoder, crtc_state, aux);
> + } else {
> + drm_dbg_kms(&i915->drm, "FEC detected status read error: %d\n", status);
> + }
> + } while (retrycount++ < FEC_RETRY_COUNT);
Please use a regular for loop with for (i = 0; i < N; i++) so even I can
look at it and know in an instant how many times it's going to loop.
> +
> + drm_err(&i915->drm, "FEC enable Failed after Retry\n");
> +}
> +
There's just way, way too much duplication between the above two
functions and the existing intel_ddi_wait_for_fec_status() and
wait_for_fec_detected(). We'll want *one* code path with the retry baked
in, with no retries for older platforms.
BR,
Jani.
> static void wait_for_fec_detected(struct drm_dp_aux *aux, bool enabled)
> {
> struct drm_i915_private *i915 = to_i915(aux->drm_dev);
> @@ -2303,8 +2356,12 @@ void intel_ddi_wait_for_fec_status(struct intel_encoder *encoder,
> * At least the Synoptics MST hub doesn't set the detected flag for
> * FEC decoding disabling so skip waiting for that.
> */
> - if (enabled)
> - wait_for_fec_detected(&intel_dp->aux, enabled);
> + if (enabled) {
> + if (DISPLAY_VER(i915) >= 30)
> + wait_for_fec_detected_with_retry(encoder, crtc_state, &intel_dp->aux);
> + else
> + wait_for_fec_detected(&intel_dp->aux, enabled);
> + }
> }
>
> static void intel_ddi_enable_fec(struct intel_encoder *encoder,
--
Jani Nikula, Intel
