linux-kernel - Re: [PATCH v3 12/15] drm/bridge: Add ITE IT6263 LVDS to HDMI converter

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Message-ID: <889594b9-e6cb-4d90-b959-cd0258b2f166@nxp.com>
Date: Tue, 22 Oct 2024 15:36:47 +0800
From: Liu Ying <victor.liu@....com>
To: Maxime Ripard <mripard@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
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Subject: Re: [PATCH v3 12/15] drm/bridge: Add ITE IT6263 LVDS to HDMI
 converter

Hi Maxime,

On 10/21/2024, Maxime Ripard wrote:
> On Mon, Oct 21, 2024 at 02:44:43PM +0800, Liu Ying wrote:
>> +static int it6263_bridge_atomic_check(struct drm_bridge *bridge,
>> +				      struct drm_bridge_state *bridge_state,
>> +				      struct drm_crtc_state *crtc_state,
>> +				      struct drm_connector_state *conn_state)
>> +{
>> +	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
>> +	int ret;
>> +
>> +	ret = drm_atomic_helper_connector_hdmi_check(conn_state->connector,
>> +						     conn_state->state);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return mode->clock > MAX_PIXEL_CLOCK_KHZ ? -EINVAL : 0;
> 
> drm_atomic_helper_connector_hdmi_check will already make that check, so
> it's redundant.

MAX_PIXEL_CLOCK_KHZ is 150MHz. With 150MHz pixel clock rate, we'll get
150MHz HDMI character rate for 8bpc and 187.5MHz HDMI character rate
for 10bpc, both are lower than MAX_HDMI_TMDS_CHAR_RATE_HZ = 225MHz.

So, it looks like pixel clock rate is the bottleneck.
Remove drm_atomic_helper_connector_hdmi_check() or keep this as-is?

> 
> Once fixed
> Acked-by: Maxime Ripard <mripard@...nel.org>
> 
> Maxime

-- 
Regards,
Liu Ying