linux-kernel - Re: [PATCH] drm/bridge: synopsys/dw-hdmi: set cec clock rate

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Date:   Sun, 13 Mar 2022 08:56:55 -0400
From:   Peter Geis <pgwipeout@...il.com>
To:     Piotr Oniszczuk <piotr.oniszczuk@...il.com>
Cc:     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>,
        Pierre-Hugues Husson <phh@....me>,
        Archit Taneja <architt@...eaurora.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Robin Murphy <robin.murphy@....com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Heiko Stübner <heiko@...ech.de>,
        dri-devel@...ts.freedesktop.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/bridge: synopsys/dw-hdmi: set cec clock rate

On Sun, Mar 13, 2022 at 6:13 AM Piotr Oniszczuk
<piotr.oniszczuk@...il.com> wrote:
>
>
>
> > Wiadomość napisana przez Peter Geis <pgwipeout@...il.com> w dniu 26.01.2022, o godz. 21:24:
> >
> > The hdmi-cec clock must be 32khz in order for cec to work correctly.
> > Ensure after enabling the clock we set it in order for the hardware to
> > work as expected.
> > Warn on failure, in case this is a static clock that is slighty off.
> > Fixes hdmi-cec support on Rockchip devices.
> >
> > Fixes: ebe32c3e282a ("drm/bridge: synopsys/dw-hdmi: Enable cec clock")
> >
> > Signed-off-by: Peter Geis <pgwipeout@...il.com>
> > ---
> > drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > index 54d8fdad395f..1a96da60e357 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -48,6 +48,9 @@
> >
> > #define HDMI14_MAX_TMDSCLK    340000000
> >
> > +/* HDMI CEC needs a clock rate of 32khz */
> > +#define HDMI_CEC_CLK_RATE    32768
> > +
> > enum hdmi_datamap {
> >       RGB444_8B = 0x01,
> >       RGB444_10B = 0x03,
> > @@ -3347,6 +3350,10 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
> >                               ret);
> >                       goto err_iahb;
> >               }
> > +
> > +             ret = clk_set_rate(hdmi->cec_clk, HDMI_CEC_CLK_RATE);
> > +             if (ret)
> > +                     dev_warn(hdmi->dev, "Cannot set HDMI cec clock rate: %d\n", ret);
> >       }
> >
> >       /* Product and revision IDs */
> > --
> > 2.25.1
> >
> >
> > _______________________________________________
> > Linux-rockchip mailing list
> > Linux-rockchip@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-rockchip
>
> Peter,
>
> On my 5.17-rc7 with applied rk356x VOP2 v8 series - this patch makes CEC working on rk3566.
> Unfortunately it breaks working ok CEC on rk3399 rockpi-4b.
>
> Reverting this patch brings back CEC on rk3399 - but rk3366 becomes with non working CEC
>
> I'm not sure how to move forward with this....

I was worried about that, thanks for testing it.
Can you send me the cec_clk rate before and after this patch?

>
> br

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