linux-kernel - Re: [PATCH v6 3/3] drm/tidss: oldi: Add atomic

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Message-ID: <20250915-benevolent-military-penguin-d64871@penduick>
Date: Mon, 15 Sep 2025 09:57:18 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Swamil Jain <s-jain1@...com>
Cc: jyri.sarha@....fi, tomi.valkeinen@...asonboard.com, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	aradhya.bhatia@...ux.dev, h-shenoy@...com, devarsht@...com, vigneshr@...com, 
	praneeth@...com, u-kumar1@...com, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/3] drm/tidss: oldi: Add atomic_check hook for oldi
 bridge

On Thu, Sep 11, 2025 at 04:37:15PM +0530, Swamil Jain wrote:
> From: Jayesh Choudhary <j-choudhary@...com>
> 
> Since OLDI consumes DSS VP clock directly as serial clock, mode_valid()
> check cannot be performed in tidss driver which should be checked
> in OLDI driver.
> 
> Fixes: 7246e0929945 ("drm/tidss: Add OLDI bridge support")
> Tested-by: Michael Walle <mwalle@...nel.org>
> Reviewed-by: Devarsh Thakkar <devarsht@...com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> Signed-off-by: Swamil Jain <s-jain1@...com>
> ---
>  drivers/gpu/drm/tidss/tidss_oldi.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_oldi.c b/drivers/gpu/drm/tidss/tidss_oldi.c
> index 7ecbb2c3d0a2..ada691839ef3 100644
> --- a/drivers/gpu/drm/tidss/tidss_oldi.c
> +++ b/drivers/gpu/drm/tidss/tidss_oldi.c
> @@ -309,6 +309,26 @@ static u32 *tidss_oldi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>  	return input_fmts;
>  }
>  
> +static int tidss_oldi_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 tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
> +	struct drm_display_mode *adjusted_mode;
> +	unsigned long round_clock;
> +
> +	adjusted_mode = &crtc_state->adjusted_mode;
> +	round_clock = clk_round_rate(oldi->serial, adjusted_mode->clock * 7 * 1000);
> +	/*
> +	 * To keep the check consistent with dispc_vp_set_clk_rate(),
> +	 * we use the same 5% check here.
> +	 */
> +	if (dispc_pclk_diff(adjusted_mode->clock * 7 * 1000, round_clock) > 5)
> +		return -EINVAL;
> +	return 0;
> +}
> +

If you're introducing that check to tidss, please use .5% like everyone
else. I understand that you don't want to change tilcdc to avoid any
regression, but that's not the case here

Maxime

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