linux-kernel - Re: [PATCH v4] phy: dphy: Correct clk

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Date:   Wed, 2 Feb 2022 20:52:01 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Liu Ying <victor.liu@....com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-phy@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-imx@....com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kishon Vijay Abraham I <kishon@...com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Maxime Ripard <mripard@...nel.org>,
        Guido Günther <agx@...xcpu.org>,
        Wyon Bi <bivvy.bi@...k-chips.com>
Subject: Re: [PATCH v4] phy: dphy: Correct clk_pre parameter

On 24-01-22, 10:40, Liu Ying wrote:
> The D-PHY specification (v1.2) explicitly mentions that the T-CLK-PRE
> parameter's unit is Unit Interval(UI) and the minimum value is 8.  Also,
> kernel doc of the 'clk_pre' member of struct phy_configure_opts_mipi_dphy
> mentions that it should be in UI.  However, the dphy core driver wrongly
> sets 'clk_pre' to 8000, which seems to hint that it's in picoseconds.
> 
> So, let's fix the dphy core driver to correctly reflect the T-CLK-PRE
> parameter's minimum value according to the D-PHY specification.
> 
> I'm assuming that all impacted custom drivers shall program values in
> TxByteClkHS cycles into hardware for the T-CLK-PRE parameter.  The D-PHY
> specification mentions that the frequency of TxByteClkHS is exactly 1/8
> the High-Speed(HS) bit rate(each HS bit consumes one UI).  So, relevant
> custom driver code is changed to program those values as
> DIV_ROUND_UP(cfg->clk_pre, BITS_PER_BYTE), then.
> 
> Note that I've only tested the patch with RM67191 DSI panel on i.MX8mq EVK.
> Help is needed to test with other i.MX8mq, Meson and Rockchip platforms,
> as I don't have the hardwares.

Applied, thanks

-- 
~Vinod