linux-kernel - Re: [PATCH 1/2] drm/bridge: parade-ps8640: Use regmap APIs

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Date:   Thu, 9 Sep 2021 14:14:29 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Philip Chen <philipchen@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/2] drm/bridge: parade-ps8640: Use regmap APIs

Hi,

On Thu, Sep 9, 2021 at 12:09 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Philip Chen (2021-09-09 11:29:19)
> > Hi,
> >
> > On Wed, Sep 8, 2021 at 2:54 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > >
> > > Quoting Philip Chen (2021-09-08 11:18:05)
> > > > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > > > index 685e9c38b2db..a16725dbf912 100644
> > > > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > > > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > > > @@ -64,12 +65,29 @@ struct ps8640 {
> > > >         struct drm_bridge *panel_bridge;
> > > >         struct mipi_dsi_device *dsi;
> > > >         struct i2c_client *page[MAX_DEVS];
> > > > +       struct regmap   *regmap[MAX_DEVS];
> > > >         struct regulator_bulk_data supplies[2];
> > > >         struct gpio_desc *gpio_reset;
> > > >         struct gpio_desc *gpio_powerdown;
> > > >         bool powered;
> > > >  };
> > > >
> > > > +static const struct regmap_range ps8640_volatile_ranges[] = {
> > > > +       { .range_min = 0, .range_max = 0xff },
> > >
> > > Is the plan to fill this out later or is 0xff the max register? If it's
> > > the latter then I think adding the max register to regmap_config is
> > > simpler.
> > It's the former.
> > The real accessible register range is different per page, E.g.:
> > - For page0, the register range is 0x00 - 0xbf.
> > - For page1, the register range is 0x00 - 0xff.
> > - For page2, the register range is 0x80 - 0xff.
>
> Oh does this have register pages? regmap has support for pages where you
> write some indirection register and then access the same i2c address for
> the next page. This looks different though and has a different i2c
> address for each page?

I haven't looked in tons of detail, but I think the right solution
here is a separate regmap config per page.

-Doug