Re: [PATCH 3/3] OMAPDSS: HDMI: Cache EDID

On 28 June 2012 15:44, Tomi Valkeinen [off-list ref] wrote:

On Thu, 2012-06-28 at 15:18 +0530, Jassi Brar wrote:

quoted

quoted

quoted

--- a/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
+++ b/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c

@@ -243,10 +243,13 @@ static int hdmi_check_hpd_state(struct hdmi_ip_data *ip_data)

      hpd = gpio_get_value(ip_data->hpd_gpio);

-     if (hpd)
+     if (hpd) {
              r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_TXON);
-     else
+     } else {
+             /* Invalidate EDID Cache */
+             ip_data->edid_len = 0;
              r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_LDOON);
+     }

There's a problem with this patch, which leaves a wrong EDID in the
cache: if you first have the cable connected and hdmi is enabled, you
then turn off the HDMI display device via sysfs, we do not go to
hdmi_check_hpd_state at all. The next time hdmi is enabled, we only get
the plug-in event, and thus EDID cache is never invalidated.

If the hdmi cable is not replugged during that period, I don't see why
would you want the EDID invalidated ?

I wasn't very clear with my comment.

When the display device is disabled, we're not listening to the hpd
interrupt anymore. So when it's disabled, the cable can be replugged and
the monitor changed, and the driver won't know about it. And so it'll
return the old EDID for the new monitor.

If that could be a problem, then we already have some problem with
current omapdss.

I think among the first things, while enabling HDMI, should be to see
if there is really some display connected on the port i.e, HPD
asserted. Only if ti_hdmi_4xxx_detect() returned true, should we
proceed otherwise wait for HPQ irq.

Unconditionally invalidating edid really seems like a regression - we
impose atleast 50ms (edid read) as extra cost on
hdmi_check_hpd_state(), which kills half the purpose of this patch.