linux-kernel - Re: [PATCH] drm/bridge: ite-it6263: Support HDMI vendor specific infoframe

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Message-ID: <023ae7ec-77a5-412f-bef5-105350561354@nxp.com>
Date: Fri, 5 Sep 2025 13:46:56 +0800
From: Liu Ying <victor.liu@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.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>,
 Dmitry Baryshkov <lumag@...nel.org>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: ite-it6263: Support HDMI vendor specific
 infoframe

On 09/05/2025, Dmitry Baryshkov wrote:
> On Thu, Sep 04, 2025 at 05:10:02PM +0800, Liu Ying wrote:
>> IT6263 supports HDMI vendor specific infoframe.  The infoframe header
>> and payload are configurable via NULL packet registers.  The infoframe
>> is enabled and disabled via PKT_NULL_CTRL register.  Add the HDMI vendor
>> specific infoframe support.
>>
>> Signed-off-by: Liu Ying <victor.liu@....com>
>> ---
>>  drivers/gpu/drm/bridge/ite-it6263.c | 72 ++++++++++++++++++++++++++-----------
>>  1 file changed, 52 insertions(+), 20 deletions(-)
>>
>> +	case HDMI_INFOFRAME_TYPE_VENDOR:
>> +		const char zero_bulk[HDMI_PKT_HB_PB_CHUNK_SIZE] = { };
>> +
>> +		/* clear NULL packet registers due to undefined default value */
>> +		regmap_bulk_write(regmap, HDMI_REG_PKT_HB(0),
>> +				  zero_bulk, sizeof(zero_bulk));
> 
> What if you move this to the probe function? Then there will be no need
> to write those registers each time the infoframe is being written.

Good idea.  But looking at drm_hdmi_vendor_infoframe_from_display_mode(),
hdmi_vendor_infoframe_length() and hdmi_vendor_infoframe_pack_only(), the
payload length could be changed in runtime according to display mode's VIC
and flags(see DRM_MODE_FLAG_3D_MASK).  And, IT6263 supports HDMI1.4a 3D
formats according to it's product information[1].  So, it makes sense to
clear HDMI_REG_PKT_PB(5) and HDMI_REG_PKT_PB(6) here which map to ptr[8]
and ptr[9] in hdmi_vendor_infoframe_pack_only().  For v2, I'd move the
NULL packet registers bulk write to it6263_hdmi_config()(i.e., it6263_probe())
and write zero to HDMI_REG_PKT_PB(5) and HDMI_REG_PKT_PB(6) here.

What do you think?

[1] www.ite.com.tw/en/product/cate1/IT6263

> 
> LGTM otherwise.
> 
>> +
>> +		/* write header and payload */
>> +		regmap_bulk_write(regmap, HDMI_REG_PKT_HB(0), buffer, len);
>> +
>> +		regmap_write(regmap, HDMI_REG_PKT_NULL_CTRL,
>> +			     ENABLE_PKT | REPEAT_PKT);
>> +		break;
> 

-- 
Regards,
Liu Ying