Re: [PATCH] drm/msm/dp: skip checking LINK_STATUS_UPDATED bit

Quoting Kuogee Hsieh (2020-10-20 09:59:59)

No need to check LINK_STATuS_UPDATED bit before

LINK_STATUS_UPDATED?

return 6 bytes of link status during link training.

Why?

This patch also fix phy compliance test link rate conversion error.

How?

Signed-off-by: Kuogee Hsieh khsieh@codeaurora.org

Any Fixes: tag?

drivers/gpu/drm/msm/dp/dp_ctrl.c | 20 ++++++-------------- drivers/gpu/drm/msm/dp/dp_link.c | 24 +++++++++++------------- 2 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c index 6bdaec778c4c..76e891c91c6e 100644 --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c @@ -1061,23 +1061,15 @@ static bool dp_ctrl_train_pattern_set(struct dp_ctrl_private *ctrl, static int dp_ctrl_read_link_status(struct dp_ctrl_private *ctrl, u8 *link_status) {

•   int len = 0;
  

•   u32 const offset = DP_LANE_ALIGN_STATUS_UPDATED - DP_LANE0_1_STATUS;
  

•   u32 link_status_read_max_retries = 100;
  

•   while (--link_status_read_max_retries) {
  

•           len = drm_dp_dpcd_read_link_status(ctrl->aux,
  

•                   link_status);
  

•           if (len != DP_LINK_STATUS_SIZE) {
  

•                   DRM_ERROR("DP link status read failed, err: %d\n", len);
  

•                   return len;
  

•           }
  

•   int ret = 0, len;
  
  

•           if (!(link_status[offset] & DP_LINK_STATUS_UPDATED))
  

•                   return 0;
  

•   len = drm_dp_dpcd_read_link_status(ctrl->aux, link_status);
  

•   if (len != DP_LINK_STATUS_SIZE) {
  

•           DRM_ERROR("DP link status read failed, err: %d\n", len);
  

•           ret = len;
  

Could this be positive if the len is greater than 0 but not DP_LINK_STATUS_SIZE? Maybe the check should be len < 0? We certainly don't want to return some smaller size from this function, right?

    }

•   return -ETIMEDOUT;
  

•   return ret;
  

}

static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl, diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c index c811da515fb3..58d65daae3b3 100644 --- a/drivers/gpu/drm/msm/dp/dp_link.c +++ b/drivers/gpu/drm/msm/dp/dp_link.c @@ -773,7 +773,8 @@ static int dp_link_process_link_training_request(struct dp_link_private *link) link->request.test_lane_count);

    link->dp_link.link_params.num_lanes = link->request.test_lane_count;

•   link->dp_link.link_params.rate = link->request.test_link_rate;
  

•   link->dp_link.link_params.rate =
  

•           drm_dp_bw_code_to_link_rate(link->request.test_link_rate);
  

Why are we storing bw_code in test_link_rate? This looks very confusing.

    return 0;

}