| Message ID | 20240924035231.1163670-2-treapking@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Drop EDID cache for it6505/anx7625 when the bridge is powered off | expand |
On Tue, Sep 24, 2024 at 11:51:46AM GMT, Pin-yen Lin wrote: > The bridge might miss the display change events when it's powered off. > This happens when a user changes the external monitor when the system > is suspended and the embedded controller doesn't not wake AP up. > > It's also observed that one DP-to-HDMI bridge doesn't work correctly > when there is no EDID read after it is powered on. > > Drop the cache to force an EDID read after system resume to fix this. > > Fixes: 8bdfc5dae4e3 ("drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP") > Signed-off-by: Pin-yen Lin <treapking@chromium.org> > --- > > drivers/gpu/drm/bridge/analogix/anx7625.c | 1 + > 1 file changed, 1 insertion(+) > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Hi, On Mon, Sep 23, 2024 at 8:53 PM Pin-yen Lin <treapking@chromium.org> wrote: > > The bridge might miss the display change events when it's powered off. > This happens when a user changes the external monitor when the system > is suspended and the embedded controller doesn't not wake AP up. > > It's also observed that one DP-to-HDMI bridge doesn't work correctly > when there is no EDID read after it is powered on. > > Drop the cache to force an EDID read after system resume to fix this. > > Fixes: 8bdfc5dae4e3 ("drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP") > Signed-off-by: Pin-yen Lin <treapking@chromium.org> > --- > > drivers/gpu/drm/bridge/analogix/anx7625.c | 1 + > 1 file changed, 1 insertion(+) I'm not totally sure if it matters, but I wonder if you should change this to only delete the EDID cache if you're in DP mode and not eDP mode? For eDP mode the panel is not allowed to change and re-reading it needlessly seems like it would slow down things like suspend/resume. I think this would only matter if someone were using eDP panels in the "old" way (not under the aux-bus) because we don't set the "DRM_BRIDGE_OP_EDID" when we see "aux-bus", so maybe we don't care that much but still... Other than that, I know that there have been discussions in the past about EDID caches but I can't quite remember all the details. I know that panel-edp.c still caches it, so we must have concluded that it's at least fine/reasonable for panels. I don't remember whether caching is encouraged / suggested for external displays, though. Do you happen to know if it even makes a difference there (in other words, do you actually see multiple calls to read the EDID when you plug in a DP display)? -Doug
Hi, On Wed, Sep 25, 2024 at 12:43 AM Doug Anderson <dianders@chromium.org> wrote: > > Hi, > > On Mon, Sep 23, 2024 at 8:53 PM Pin-yen Lin <treapking@chromium.org> wrote: > > > > The bridge might miss the display change events when it's powered off. > > This happens when a user changes the external monitor when the system > > is suspended and the embedded controller doesn't not wake AP up. > > > > It's also observed that one DP-to-HDMI bridge doesn't work correctly > > when there is no EDID read after it is powered on. > > > > Drop the cache to force an EDID read after system resume to fix this. > > > > Fixes: 8bdfc5dae4e3 ("drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP") > > Signed-off-by: Pin-yen Lin <treapking@chromium.org> > > --- > > > > drivers/gpu/drm/bridge/analogix/anx7625.c | 1 + > > 1 file changed, 1 insertion(+) > > I'm not totally sure if it matters, but I wonder if you should change > this to only delete the EDID cache if you're in DP mode and not eDP > mode? For eDP mode the panel is not allowed to change and re-reading > it needlessly seems like it would slow down things like > suspend/resume. I think this would only matter if someone were using > eDP panels in the "old" way (not under the aux-bus) because we don't > set the "DRM_BRIDGE_OP_EDID" when we see "aux-bus", so maybe we don't > care that much but still... I'll update this in v2. > > Other than that, I know that there have been discussions in the past > about EDID caches but I can't quite remember all the details. I know > that panel-edp.c still caches it, so we must have concluded that it's > at least fine/reasonable for panels. I don't remember whether caching > is encouraged / suggested for external displays, though. Do you happen > to know if it even makes a difference there (in other words, do you > actually see multiple calls to read the EDID when you plug in a DP > display)? At least on ChromeOS, Chrome triggers two EDID reads when I plug in an external monitor. I'm not sure if this is common for other DRM masters though. > > -Doug Regards, Pin-yen
diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c index 88e4aa5830f3..b4c1f00f1c3d 100644 --- a/drivers/gpu/drm/bridge/analogix/anx7625.c +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c @@ -2561,6 +2561,7 @@ static int __maybe_unused anx7625_runtime_pm_suspend(struct device *dev) mutex_lock(&ctx->lock); anx7625_stop_dp_work(ctx); + anx7625_remove_edid(ctx); anx7625_power_standby(ctx); mutex_unlock(&ctx->lock);
The bridge might miss the display change events when it's powered off. This happens when a user changes the external monitor when the system is suspended and the embedded controller doesn't not wake AP up. It's also observed that one DP-to-HDMI bridge doesn't work correctly when there is no EDID read after it is powered on. Drop the cache to force an EDID read after system resume to fix this. Fixes: 8bdfc5dae4e3 ("drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP") Signed-off-by: Pin-yen Lin <treapking@chromium.org> --- drivers/gpu/drm/bridge/analogix/anx7625.c | 1 + 1 file changed, 1 insertion(+)