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

[Maxime Ripard]

On Tue, Nov 18, 2025 at 02:36:09PM -0600, Chris Morgan wrote:
> 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.

Yep, that's what you should be testing for :)

Maxime
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 273 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-rockchip/attachments/20251119/93bb5054/attachment-0001.sig>