linux-kernel - Re: [linux-sunxi] Re: [PATCH 04/12] drm/sun4i: sun6i_mipi

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Date:   Fri, 28 Sep 2018 00:33:39 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Jagan Teki <jagan@...rulasolutions.com>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] Re: [PATCH 04/12] drm/sun4i: sun6i_mipi_dsi: Enable
 missing DSI bus clock

On Fri, Sep 28, 2018 at 12:26 AM Jagan Teki <jagan@...rulasolutions.com> wrote:
>
> On Thu, Sep 27, 2018 at 7:47 PM Chen-Yu Tsai <wens@...e.org> wrote:
> >
> > On Thu, Sep 27, 2018 at 9:44 PM Jagan Teki <jagan@...rulasolutions.com> wrote:
> > >
> > > On Thu, Sep 27, 2018 at 6:13 PM Chen-Yu Tsai <wens@...e.org> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Thu, Sep 27, 2018 at 7:49 PM Jagan Teki <jagan@...rulasolutions.com> wrote:
> > > > >
> > > > > DSI bus_clk is already available in sun6i_dsi but missed to
> > > > > get the clk and process for enable/disable.
> > > > >
> > > > > This patch add support for it.
> > > > >
> > > > > Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> > > > > ---
> > > > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 8 ++++++++
> > > > >  1 file changed, 8 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > index 8e9c76febca2..156b371243c6 100644
> > > > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > @@ -1004,6 +1004,12 @@ static int sun6i_dsi_probe(struct platform_device *pdev)
> > > > >                 return PTR_ERR(dsi->reset);
> > > > >         }
> > > > >
> > > > > +       dsi->bus_clk = devm_clk_get(dev, "bus");
> > > > > +       if (IS_ERR(dsi->bus_clk)) {
> > > > > +               dev_err(dev, "Couldn't get the DSI bus clock\n");
> > > > > +               return PTR_ERR(dsi->bus_clk);
> > > > > +       }
> > > > > +
> > > >
> > > > The DSI driver uses devm_regmap_init_mmio_clk, which enables the
> > > > clock behind the scenes when regmap access needs it enabled.
> > > >
> > > > Did you have any issues without this patch?
> > >
> > > I'm unable to read register values via devmem, I see all 0's for all
> > > dsi reg space.
> >
> > Well that is to be expected given how mmio with clk regmap works.
> > Did you encounter any other problems besides this?
>
> no
>
> >
> > FYI you can dump regmap contents using /sys/kernel/debug/regmap/*/registers
>
> Thanks, but ccu not using regmap I believe so can't see bus enabled
> bit set via devmap
> # devmem 0x01C20060
> 0x33800000

That is perfectly normal. It is only enabled when there are accesses to the
DSI regmap.

ChenYu