linux-kernel - Re: [PATCH v5 07/13] drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready

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Message-ID: <c0784c5e-fc71-64c5-e09f-63e1abd1b61d@ti.com>
Date: Tue, 22 Oct 2024 11:55:25 +0530
From: Devarsh Thakkar <devarsht@...com>
To: Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
        Tomi Valkeinen
	<tomi.valkeinen@...asonboard.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>,
        Laurent Pinchart
	<laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>
CC: Dominik Haller <d.haller@...tec.de>, Sam Ravnborg <sam@...nborg.org>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Nishanth Menon
	<nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
        Praneeth Bajjuri
	<praneeth@...com>, Udit Kumar <u-kumar1@...com>,
        Jayesh Choudhary
	<j-choudhary@...com>,
        DRI Development List <dri-devel@...ts.freedesktop.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 07/13] drm/bridge: cdns-dsi: Wait for Clk and Data
 Lanes to be ready

Hi Aradhya,

Thanks for the patch.

On 20/10/24 01:24, Aradhya Bhatia wrote:
> From: Aradhya Bhatia <a-bhatia1@...com>

[...]

> +	/*
> +	 * Now that the DSI Link and DSI Phy are initialized,
> +	 * wait for the CLK and Data Lanes to be ready.
> +	 */
> +	tmp = CLK_LANE_RDY;
> +	for (int i = 0; i < nlanes; i++)
> +		tmp |= DATA_LANE_RDY(i);
> +
> +	if (readl_poll_timeout(dsi->regs + MCTL_MAIN_STS, status,
> +			       status & tmp, 100, 500000))

The above would mark the condition as true even if one data lane gets ready. I
think we need to poll until all data lanes are marked as ready. Also good to
give a warning in case we time out.

IMHO below should fix this:
        WARN_ON_ONCE(readl_poll_timeout(dsi->regs + MCTL_MAIN_STS, status,
                                       (tmp == (status & tmp)), 100, 0));

Regards
Devarsh