On Thu 06 Jan 12:44 PST 2022, Kuogee Hsieh wrote:

DP CTS test case 4.2.2.6 has valid edid with bad checksum on purpose and expect DP source return correct checksum. During drm edid read, correct edid checksum is calculated and stored at connector::real_edid_checksum.

Interesting, thanks for adding this!

Reviewed-by: Bjorn Andersson bjorn.andersson@linaro.org

Regards, Bjorn

The problem is struct dp_panel::connector never be assigned, instead the connector is stored in struct msm_dp::connector. When we run compliance testing test case 4.2.2.6 dp_panel_handle_sink_request() won't have a valid edid set in struct dp_panel::edid so we'll try to use the connectors real_edid_checksum and hit a NULL pointer dereference error because the connector pointer is never assigned.

Changes in V2: -- populate panel connector at msm_dp_modeset_init() instead of at dp_panel_read_sink_caps()

Changes in V3: -- remove unhelpful kernel crash trace commit text -- remove renaming dp_display parameter to dp

Changes in V4: -- add more details to commit text

Fixes: 7948fe12d47 ("drm/msm/dp: return correct edid checksum after corrupted edid checksum read") Signee-off-by: Kuogee Hsieh quic_khsieh@quicinc.com

---

drivers/gpu/drm/msm/dp/dp_display.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c index 3449d3f..40a059d 100644 --- a/drivers/gpu/drm/msm/dp/dp_display.c +++ b/drivers/gpu/drm/msm/dp/dp_display.c @@ -1499,6 +1499,7 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev, struct drm_encoder *encoder) { struct msm_drm_private *priv;

• struct dp_display_private *dp_priv; int ret;

  if (WARN_ON(!encoder) || WARN_ON(!dp_display) || WARN_ON(!dev))

@@ -1507,6 +1508,8 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev, priv = dev->dev_private; dp_display->drm_dev = dev;

• dp_priv = container_of(dp_display, struct dp_display_private, dp_display);
• ret = dp_display_request_irq(dp_display); if (ret) { DRM_ERROR("request_irq failed, ret=%d\n", ret);

@@ -1524,6 +1527,8 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev, return ret; }

• dp_priv->panel->connector = dp_display->connector;
• priv->connectors[priv->num_connectors++] = dp_display->connector; return 0;

}

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