linux-kernel - Re: [PATCH] drm/bridge: sii902x: Fix mode

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Date: Fri, 3 May 2024 20:43:54 +0530
From: Jayesh Choudhary <j-choudhary@...com>
To: Maxime Ripard <mripard@...nel.org>
CC: <andrzej.hajda@...el.com>, <neil.armstrong@...aro.org>, <rfoss@...nel.org>,
        <Laurent.pinchart@...asonboard.com>, <jonas@...boo.se>,
        <jernej.skrabec@...il.com>, <maarten.lankhorst@...ux.intel.com>,
        <tzimmermann@...e.de>, <airlied@...il.com>, <daniel@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/bridge: sii902x: Fix mode_valid hook

Hello Maxime,

Thanks for the review.

On 15/04/24 13:10, Maxime Ripard wrote:
> Hi,
> 
> On Mon, Apr 08, 2024 at 01:44:35PM +0530, Jayesh Choudhary wrote:
>> Currently, mode_valid hook returns all mode as valid. Add the check
>> for the maximum and minimum pixel clock that the bridge can support
>> while validating a mode.
>>
>> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
>> ---
>>   drivers/gpu/drm/bridge/sii902x.c | 16 +++++++++++++++-
>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
>> index 8f84e98249c7..658819199c84 100644
>> --- a/drivers/gpu/drm/bridge/sii902x.c
>> +++ b/drivers/gpu/drm/bridge/sii902x.c
>> @@ -163,6 +163,16 @@
>>   
>>   #define SII902X_AUDIO_PORT_INDEX		3
>>   
>> +/*
>> + * The maximum resolution supported by the HDMI bridge is 1080p@...z
>> + * and 1920x1200 requiring a pixel clock of 165MHz and the minimum
>> + * resolution supported is 480p@...z requiring a pixel clock of 25MHz
>> + *
>> + * (drm_display_mode clock is in kHz)
>> + */
>> +#define SII902X_MIN_PIXEL_CLOCK			25000
>> +#define SII902X_MAX_PIXEL_CLOCK			165000
>> +
> 
> You should probably add a KHZ suffix or something to make it obvious.
> The natural unit for a frequency is Hertz.

Okay.
Instead of adding the kHz in comments, I will add that in suffix
like SII902X_MIN_PIXEL_CLOCK_KHZ.

> 
>>   struct sii902x {
>>   	struct i2c_client *i2c;
>>   	struct regmap *regmap;
>> @@ -313,7 +323,11 @@ static int sii902x_get_modes(struct drm_connector *connector)
>>   static enum drm_mode_status sii902x_mode_valid(struct drm_connector *connector,
>>   					       struct drm_display_mode *mode)
>>   {
>> -	/* TODO: check mode */
>> +	if (mode->clock < SII902X_MIN_PIXEL_CLOCK)
>> +		return MODE_CLOCK_LOW;
>> +
>> +	if (mode->clock > SII902X_MAX_PIXEL_CLOCK)
>> +		return MODE_CLOCK_HIGH;
>>   
>>   	return MODE_OK;
>>   }
> 
> It's something you should do in atomic_check too
> 

Like using clock from adjusted mode in crtc_state?
Will update in the next revision.

Warm Regards,
-Jayesh