linux-kernel - Re: [PATCH V3 0/7] drm: bridge: samsung-dsim: Support variable clocking

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Date:   Tue, 2 May 2023 13:40:41 -0500
From:   Adam Ford <aford173@...il.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     dri-devel@...ts.freedesktop.org, marex@...x.de,
        aford@...conembedded.com, Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 0/7] drm: bridge: samsung-dsim: Support variable clocking

On Tue, May 2, 2023 at 3:35 AM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
>
> On 02.05.2023 03:07, Adam Ford wrote:
> > This series fixes the blanking pack size and the PMS calculation.  It then
> > adds support to allows the DSIM to dynamically DPHY clocks, and support
> > non-burst mode while allowing the removal of the hard-coded clock values
> > for the PLL for imx8m mini/nano/plus, and it allows the removal of the
> > burst-clock device tree entry when burst-mode isn't supported by connected
> > devices like an HDMI brige.  In that event, the HS clock is set to the value
> > requested by the bridge chip.
> >
> > This has been tested on both an i.MX8M Nano and i.MX8M Plus, and should work
> > on i.MX8M Mini as well.
> >
> > Adam Ford (6):
> >    drm: bridge: samsung-dsim: Fix PMS Calculator on imx8m[mnp]
> >    drm: bridge: samsung-dsim: Fetch pll-clock-frequency automatically
> >    drm: bridge: samsung-dsim: Select GENERIC_PHY_MIPI_DPHY
> >    drm: bridge: samsung-dsim: Dynamically configure DPHY timing
> >    drm: bridge: samsung-dsim: Support non-burst mode
> >    drm: bridge: samsung-dsim: Let blanking calcuation work in non-burst
> >      mode
> >
> > Lucas Stach (1):
> >    drm: bridge: samsung-dsim: fix blanking packet size calculation
> >
> >   drivers/gpu/drm/bridge/Kconfig        |   1 +
> >   drivers/gpu/drm/bridge/samsung-dsim.c | 150 ++++++++++++++++++++++----
> >   include/drm/bridge/samsung-dsim.h     |   5 +
> >   3 files changed, 136 insertions(+), 20 deletions(-)
>
> Works fine (= doesn't break) on Exynos.
>
Thank is great news.  Thank you for testing!

> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

adam
>
>
> >
> > ---
> > V3:  When checking if the bust-clock is present, only check for it
> >       in the device tree, and don't check the presence of the
> >       MIPI_DSI_MODE_VIDEO_BURST flag as it breaks an existing Exynos
> >       board.
> >
> >       Add a new patch to the series to select GENERIC_PHY_MIPI_DPHY in
> >       Kconfig otherwise the build breaks on the 32-bit Exynos.
> >
> >       Change vco_min variable name to min_freq
> >
> >       Added tested-by from Chen-Yu Tsai
> >
> > V2:  Instead of using my packet blanking calculation, this integrates
> >       on from Lucas Stach which gets modified later in the series to
> >       cache the value of the HS-clock instead of having to do the
> >       calucations again.
> >
> >       Instead of completely eliminating the PLL clock frequency from
> >       the device tree, this makes it optional to avoid breaking some
> >       Samsung devices.  When the samsung,pll-clock-frequency is not
> >       found, it reads the value of the clock named "sclk_mipi"
> >       This also maintains backwords compatibility with older device
> >       trees.
> >
> >       This also changes the DPHY calcuation from a Look-up table,
> >       a reverse engineered algorithm which uses
> >       phy_mipi_dphy_get_default_config to determine the standard
> >       nominal values and calculates the cycles necessary to update
> >       the DPHY timings accordingly.
> >
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>