Re: PROBLEM: Asus C201 video mode problems on HDMI hotplug (regression)

Nick Bowler
2017-12-01T00:21:26Z

Hi,

On 2017-11-27 22:30 -0500, Nick Bowler wrote:
> A note about the test setup: I had to remove the test equipment so I
> no longer have any information about the video mode from the sink side
> (like in the photos). Thus, with the current setup, I am using the
> presense or absense of audio to determine whether the issue is present
> or not.
>
> The test procedure is: boot up, start music, then hotplug the hdmi four
> times. If sound is heard after all four connections, PASS; otherwise FAIL.
>
> - I retested on 4.15-rc1 to confirm that the issue is still present (it is).
>
> - I applied the functional revert from earlier on top of 4.15-rc1 and the
> problem is fixed.
>
> - Returning to 4.15-rc1 and applying [Laurent Pinchart's] patch --
> the issue is present again (no change in behaviour compared to
> 4.15-rc1).

Another data point... the following patch appears sufficient to restore
working behaviour.

Cheers,
Nick

---
drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 17 -----------------
1 file changed, 17 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index bf14214fa464..3118fbd8433d 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -1101,8 +1101,6 @@ static void dw_hdmi_phy_power_off(struct dw_hdmi *hdmi)
static int dw_hdmi_phy_power_on(struct dw_hdmi *hdmi)
{
const struct dw_hdmi_phy_data *phy = hdmi->phy.data;
- unsigned int i;
- u8 val;

if (phy->gen == 1) {
dw_hdmi_phy_enable_powerdown(hdmi, false);
@@ -1116,21 +1114,6 @@ static int dw_hdmi_phy_power_on(struct dw_hdmi *hdmi)
dw_hdmi_phy_gen2_txpwron(hdmi, 1);
dw_hdmi_phy_gen2_pddq(hdmi, 0);

- /* Wait for PHY PLL lock */
- for (i = 0; i < 5; ++i) {
- val = hdmi_readb(hdmi, HDMI_PHY_STAT0) & HDMI_PHY_TX_PHY_LOCK;
- if (val)
- break;
-
- usleep_range(1000, 2000);
- }
-
- if (!val) {
- dev_err(hdmi->dev, "PHY PLL failed to lock\n");
- return -ETIMEDOUT;
- }
-
- dev_dbg(hdmi->dev, "PHY PLL locked %u iterations\n", i);
return 0;
}

--
2.13.6