linux-kernel - Re: [PATCH 3/4] drm/vc4: use new helper to get ACR values

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Message-ID: <20250310-invisible-married-firefly-945c84@houat>
Date: Mon, 10 Mar 2025 15:51:53 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Dmitry Baryshkov <lumag@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, Dave Stevenson <dave.stevenson@...pberrypi.com>, 
	Maíra Canal <mcanal@...lia.com>, Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>, 
	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>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 3/4] drm/vc4: use new helper to get ACR values

On Sun, Mar 09, 2025 at 10:13:58AM +0200, Dmitry Baryshkov wrote:
> From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> 
> Use drm_hdmi_acr_get_n_cts() helper instead of calculating N and CTS
> values in the VC4 driver.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 10 +++-------
>  drivers/gpu/drm/vc4/vc4_hdmi.h |  7 +++++++
>  2 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 37238a12baa58a06a5d6f40d1ab64abc7fac60d7..f24bcc2f3a2ac39aaea061b809940978341472f4 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -1637,6 +1637,7 @@ static void vc4_hdmi_encoder_atomic_mode_set(struct drm_encoder *encoder,
>  		      &crtc_state->adjusted_mode);
>  	vc4_hdmi->output_bpc = conn_state->hdmi.output_bpc;
>  	vc4_hdmi->output_format = conn_state->hdmi.output_format;
> +	vc4_hdmi->tmds_char_rate = conn_state->hdmi.tmds_char_rate;
>  	mutex_unlock(&vc4_hdmi->mutex);
>  }
>  
> @@ -1829,17 +1830,12 @@ static void vc4_hdmi_audio_set_mai_clock(struct vc4_hdmi *vc4_hdmi,
>  
>  static void vc4_hdmi_set_n_cts(struct vc4_hdmi *vc4_hdmi, unsigned int samplerate)
>  {
> -	const struct drm_display_mode *mode = &vc4_hdmi->saved_adjusted_mode;
> -	u32 n, cts;
> -	u64 tmp;
> +	unsigned int n, cts;
>  
>  	lockdep_assert_held(&vc4_hdmi->mutex);
>  	lockdep_assert_held(&vc4_hdmi->hw_lock);
>  
> -	n = 128 * samplerate / 1000;
> -	tmp = (u64)(mode->clock * 1000) * n;
> -	do_div(tmp, 128 * samplerate);
> -	cts = tmp;
> +	drm_hdmi_acr_get_n_cts(vc4_hdmi->tmds_char_rate, samplerate, &n, &cts);
>  
>  	HDMI_WRITE(HDMI_CRP_CFG,
>  		   VC4_HDMI_CRP_CFG_EXTERNAL_CTS_EN |
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> index e3d989ca302b72533c374dfa3fd0d5bd7fe64a82..0a775dbfe99d45521f3d0a2016555aefa81d7934 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> @@ -211,6 +211,13 @@ struct vc4_hdmi {
>  	 * KMS hooks. Protected by @mutex.
>  	 */
>  	enum hdmi_colorspace output_format;
> +
> +	/**
> +	 * @tmds_char_rate: Copy of
> +	 * @drm_connector_state.hdmi.tmds_char_rate for use outside of
> +	 * KMS hooks. Protected by @mutex.
> +	 */
> +	unsigned long long tmds_char_rate;
>  };

This should be in drm_connector_hdmi if it's useful

Maxime

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