linux-kernel - Re: [PATCH v3 2/6] drm/bridge: dw-hdmi-qp: Fixup timer base setup

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Message-ID: <80932583-5055-420b-bd92-9ee9ec7d6c1a@collabora.com>
Date: Wed, 3 Sep 2025 22:03:59 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Daniel Stone <daniel@...ishbar.org>
Cc: Sandy Huang <hjc@...k-chips.com>, Heiko Stübner
 <heiko@...ech.de>, Andy Yan <andy.yan@...k-chips.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/6] drm/bridge: dw-hdmi-qp: Fixup timer base setup

Hi Daniel,

On 8/29/25 6:21 PM, Daniel Stone wrote:
> Hi Cristian,
> 
> On Mon, 25 Aug 2025 at 10:57, Cristian Ciocaltea
> <cristian.ciocaltea@...labora.com> wrote:
>> @@ -1255,6 +1254,11 @@ struct dw_hdmi_qp *dw_hdmi_qp_bind(struct platform_device *pdev,
>>                 return ERR_PTR(-ENODEV);
>>         }
>>
>> +       if (!plat_data->ref_clk_rate) {
>> +               dev_err(dev, "Missing ref_clk rate\n");
>> +               return ERR_PTR(-ENODEV);
>> +       }
> 
> This introduces another bisect cliff, as the Rockchip integration
> isn't added until patch 5/6, meaning together with the previous patch
> the driver isn't usable between patches 1-5. It would be most sensible
> I think to keep a default until the users have been fixed up. But
> maybe a better sequence for this series would be:
> * dev_err_probe() cleanup (easy, no dependencies)
> * add refclk to plat_data (populated but unused)
> * use refclk instead of hardcoded frequency in bridge driver, make it mandatory
> * add CEC IRQ to plat_data (populated but unused)
> * add CEC support to driver, probably make it not mandatory to provide
> CEC IRQ in DT since it doesn't seem required for correct operation?
> * enable CEC in defconfig

Yeah, this is pretty similar to how the initial series looked like.  The
current sequence follows Heiko's suggestion, which I (still) think it's the
correct approach.

Both bisect issues are now fixed in v4:

https://lore.kernel.org/all/20250903-rk3588-hdmi-cec-v4-0-fa25163c4b08@collabora.com/

Thanks for the review!

Regards,
Cristian