[PATCH v2 2/3] drm/bridge: dw-hdmi-qp: Add support for missing HPD

[Chris Morgan]

On Tue, Nov 18, 2025 at 09:46:04AM +0100, Maxime Ripard wrote:
> Hi,
> 
> On Thu, Nov 13, 2025 at 01:29:38PM -0600, Chris Morgan wrote:
> > From: Chris Morgan <macromorgan at hotmail.com>
> > 
> > Add support for the dw-hdmi-qp driver to handle devices with missing
> > HPD pins.
> > 
> > Since in this situation we are now polling for the EDID data via i2c
> > change the error message to a debug message when we are unable to
> > complete an i2c read, as a disconnected device would otherwise fill
> > dmesg with i2c read errors.
> > 
> > Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
> 
> You must also disable any mode using the scrambler when there's no
> hotplug interrupt available.

Is there a simple way to do that? I'm not seeing any references to
scrambling in the current driver.

Should I just limit the rate to HDMI14_MAX_TMDSCLK (340000000)  under
dw_hdmi_qp_bridge_tmds_char_rate_valid() if using EDID polling? A
document I found online from Synopsys [1] claims that scrambling is
used by default at rates above 340 (if I'm reading it right) and used
opportunistically at rates below 340.

Thank you,
Chris

[1] https://www.synopsys.com/blogs/chip-design/hdmi-scrambling-higher-data-rates.html

> 
> Maxime