linux-kernel - Re: [PATCH v3 2/3] drm/bridge: nwl-dsi: Remove a check on unchanged HS clock rate from ->mode

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Message-ID: <176671b3-b0f8-d1be-79a1-ebf8ee9123e9@baylibre.com>
Date:   Fri, 30 Apr 2021 10:35:10 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Liu Ying <victor.liu@....com>, dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, a.hajda@...sung.com,
        robert.foss@...aro.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...l.net, airlied@...ux.ie,
        daniel@...ll.ch, agx@...xcpu.org, robert.chiras@....com,
        linux-imx@....com
Subject: Re: [PATCH v3 2/3] drm/bridge: nwl-dsi: Remove a check on unchanged
 HS clock rate from ->mode_set()

On 23/04/2021 11:26, Liu Ying wrote:
> The check on unchanged HS clock rate in ->mode_set() improves
> the callback's performance a bit by early return.  However,
> the up-coming patch would get MIPI DSI controller and PHY ready
> in ->mode_set() after that check, thus likely skipped.
> So, this patch removes that check to make sure MIPI DSI controller
> and PHY will be brought up and taken down from ->mode_set() and
> ->atomic_disable() respectively in pairs.
> 
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Neil Armstrong <narmstrong@...libre.com>
> Cc: Robert Foss <robert.foss@...aro.org>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Jonas Karlman <jonas@...boo.se>
> Cc: Jernej Skrabec <jernej.skrabec@...l.net>
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Guido Günther <agx@...xcpu.org>
> Cc: Robert Chiras <robert.chiras@....com>
> Cc: NXP Linux Team <linux-imx@....com>
> Signed-off-by: Liu Ying <victor.liu@....com>
> ---
> v2->v3:
> * Split from the single patch in v2 to clarify changes. (Neil)
> 
>  drivers/gpu/drm/bridge/nwl-dsi.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/nwl-dsi.c b/drivers/gpu/drm/bridge/nwl-dsi.c
> index c65ca860712d2..601ccc4a7cdc7 100644
> --- a/drivers/gpu/drm/bridge/nwl-dsi.c
> +++ b/drivers/gpu/drm/bridge/nwl-dsi.c
> @@ -856,13 +856,6 @@ nwl_dsi_bridge_mode_set(struct drm_bridge *bridge,
>  	if (ret < 0)
>  		return;
>  
> -	/*
> -	 * If hs clock is unchanged, we're all good - all parameters are
> -	 * derived from it atm.
> -	 */
> -	if (new_cfg.mipi_dphy.hs_clk_rate == dsi->phy_cfg.mipi_dphy.hs_clk_rate)
> -		return;
> -
>  	phy_ref_rate = clk_get_rate(dsi->phy_ref_clk);
>  	DRM_DEV_DEBUG_DRIVER(dev, "PHY at ref rate: %lu\n", phy_ref_rate);
>  	/* Save the new desired phy config */
> 

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>