linux-kernel - Re: [PATCH 02/10] phy: Add configuration interface

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Message-ID: <20180921141805.s4u224xzmtii66dg@flea>
Date:   Fri, 21 Sep 2018 16:18:05 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        Krzysztof Witos <kwitos@...ence.com>,
        Rafal Ciepiela <rafalc@...ence.com>
Subject: Re: [PATCH 02/10] phy: Add configuration interface

On Wed, Sep 19, 2018 at 02:14:36PM +0200, Maxime Ripard wrote:
> > I'm sorry but I'm not convinced a consumer driver should have all the details
> > that are added in phy_configure_opts_mipi_dphy.
> 
> If it can convince you, here is the parameters that are needed by all
> the MIPI-DSI drivers currently in Linux to configure their PHY:
> 
>   - cdns-dsi (drivers/gpu/drm/bridge/cdns-dsi.c)
>     - hs_clk_rate
>     - lanes
>     - videomode
> 
>   - kirin (drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c)
>     - hs_exit
>     - hs_prepare
>     - hs_trail
>     - hs_zero
>     - lpx
>     - ta_get
>     - ta_go
>     - wakeup
> 
>   - msm (drivers/gpu/drm/msm/dsi/*)
>     - clk_post
>     - clk_pre
>     - clk_prepare
>     - clk_trail
>     - clk_zero
>     - hs_clk_rate
>     - hs_exit
>     - hs_prepare
>     - hs_trail
>     - hs_zero
>     - lp_clk_rate
>     - ta_get
>     - ta_go
>     - ta_sure
> 
>   - mtk (drivers/gpu/drm/mediatek/mtk_dsi.c)
>     - hs_clk_rate
>     - hs_exit
>     - hs_prepare
>     - hs_trail
>     - hs_zero
>     - lpx
> 
>   - sun4i (drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c)
>     - clk_post
>     - clk_pre
>     - clk_prepare
>     - clk_zero
>     - hs_prepare
>     - hs_trail
>     - lanes
>     - lp_clk_rate
> 
>   - tegra (drivers/gpu/drm/tegra/dsi.c)
>     - clk_post
>     - clk_pre
>     - clk_prepare
>     - clk_trail
>     - clk_zero
>     - hs_exit
>     - hs_prepare
>     - hs_trail
>     - hs_zero
>     - lpx
>     - ta_get
>     - ta_go
>     - ta_sure
> 
>   - vc4 (drivers/gpu/drm/vc4/vc4_dsi.c)
>     - hs_clk_rate
>     - lanes
> 
> Now, for MIPI-CSI receivers:
> 
>   - marvell-ccic (drivers/media/platform/marvell-ccic/mcam-core.c)
>     - clk_term_en
>     - clk_settle
>     - d_term_en
>     - hs_settle
>     - lp_clk_rate
> 
>   - omap4iss (drivers/staging/media/omap4iss/iss_csiphy.c)
>     - clk_miss
>     - clk_settle
>     - clk_term
>     - hs_settle
>     - hs_term
>     - lanes
> 
>   - rcar-vin (drivers/media/platform/rcar-vin/rcar-csi2.c)
>     - hs_clk_rate
>     - lanes
> 
>   - ti-vpe (drivers/media/platform/ti-vpe/cal.c)
>     - clk_term_en
>     - d_term_en
>     - hs_settle
>     - hs_term
> 
> So the timings expressed in the structure are the set of all the ones
> currently used in the tree by DSI and CSI drivers. I would consider
> that a good proof that it would be useful.
> 
> Note that at least cdns-dsi, exynos4-is
> (drivers/media/platform/exynos4-is/mipi-csis.c), kirin, sun4i, msm,
> mtk, omap4iss, plus the v4l2 drivers cdns-csi2tx and cdns-csi2rx I
> want to convert, have already either a driver for their DPHY using the
> phy framework plus a configuration function, or a design very similar
> that could be migrated to such an API.

There's also a patch set currently being submitted that uses a phy
driver + custom functions:
https://lore.kernel.org/patchwork/cover/988959/

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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