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From:   Nicolas Boichat <drinkcat@chromium.org>
Date:   Mon, 18 Feb 2019 07:43:38 +0800
Message-ID: <CANMq1KD9QsmeB0D-GW1pvpDsNER7y23mep8Yf-VPveL+mTELwg@mail.gmail.com>
Subject: Re: [PATCH 3/3] drm/mediatek: add mt8183 dsi driver support
To:     Jitao Shi <jitao.shi@mediatek.com>
Cc:     Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
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On Sun, Feb 17, 2019 at 10:48 PM Jitao Shi <jitao.shi@mediatek.com> wrote:
>
> On Thu, 2019-02-14 at 13:54 +0800, Nicolas Boichat wrote:
> > On Thu, Feb 14, 2019 at 12:43 PM Jitao Shi <jitao.shi@mediatek.com> wrote:
> > >
> > > MT8183 dsi has two changes with mt8173.
> > > 1. Add the register double buffer control, but we no need it, So make
> > >    it default off.
> >
> > Can you describe a little bit more what this is about? That's shadow
> > registers, right?
> >
>
> Yes, it is shadow registers.
>
> Jitao
>
> > > 2. Add picture size control.
> > >
> > > Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_dsi.c | 20 +++++++++++++++++++-
> > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > index 80db02a25cb0..20cb53f05d42 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > @@ -78,6 +78,7 @@
> > >  #define DSI_VBP_NL             0x24
> > >  #define DSI_VFP_NL             0x28
> > >  #define DSI_VACT_NL            0x2C
> > > +#define DSI_SIZE_CON           0x38
> > >  #define DSI_HSA_WC             0x50
> > >  #define DSI_HBP_WC             0x54
> > >  #define DSI_HFP_WC             0x58
> > > @@ -131,7 +132,10 @@
> > >  #define VM_CMD_EN                      BIT(0)
> > >  #define TS_VFP_EN                      BIT(5)
> > >
> > > -#define DSI_CMDQ0              0x180
> >
> > As I said earlier, move this to 2/3.
> >
>
> Thank for you review.
> I'll move it to 2/3 next version.
>
> Best Regards
> Jitao
>
> > > +#define DSI_SHADOW_DEBUG       0x190U
> > > +#define FORCE_COMMIT           BIT(0)
> > > +#define BYPASS_SHADOW          BIT(1)
> > > +
> > >  #define CONFIG                         (0xff << 0)
> > >  #define SHORT_PACKET                   0
> > >  #define LONG_PACKET                    2
> > > @@ -158,6 +162,7 @@ struct phy;
> > >
> > >  struct mtk_dsi_driver_data {
> > >         const u32 reg_cmdq_off;
> > > +       bool has_size_ctl;
> > >  };
> > >
> > >  struct mtk_dsi {
> > > @@ -426,6 +431,9 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
> > >         writel(vm->vfront_porch, dsi->regs + DSI_VFP_NL);
> > >         writel(vm->vactive, dsi->regs + DSI_VACT_NL);
> > >
> > > +       if (dsi->driver_data->has_size_ctl)
> > > +               writel(vm->vactive << 16 | vm->hactive, dsi->regs + DSI_SIZE_CON);
> > > +
> > >         horizontal_sync_active_byte = (vm->hsync_len * dsi_tmp_buf_bpp - 10);
> > >
> > >         if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> > > @@ -595,6 +603,9 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
> > >         }
> > >
> > >         mtk_dsi_enable(dsi);
> > > +
> > > +       /* DSI no need this double buffer, disable it when writing register */
> >
> > "DSI does not need double buffering, disable it when writing register"
> >
>
> I'll fix it next version.

In that case, please say something about "shadow registers". (maybe
it's just me, but usually double-buffering is associated with
framebuffer data, not register settings)

> > > +       writel(FORCE_COMMIT | BYPASS_SHADOW, dsi->regs + DSI_SHADOW_DEBUG);
> >
> > So you do this on all MT* variants, is that ok?
> >
> > >         mtk_dsi_reset_engine(dsi);
> > >         mtk_dsi_phy_timconfig(dsi);
> > >
> > > @@ -1090,11 +1101,18 @@ static const struct mtk_dsi_driver_data mt2701_dsi_driver_data = {
> > >         .reg_cmdq_off = 0x180,
> > >  };
> > >
> > > +static const struct mtk_dsi_driver_data mt8183_dsi_driver_data = {
> > > +       .reg_cmdq_off = 0x200,
> > > +       .has_size_ctl = true,
> > > +};
> > > +
> > >  static const struct of_device_id mtk_dsi_of_match[] = {
> > >         { .compatible = "mediatek,mt2701-dsi",
> > >           .data = &mt2701_dsi_driver_data },
> > >         { .compatible = "mediatek,mt8173-dsi",
> > >           .data = &mt8173_dsi_driver_data },
> > > +       { .compatible = "mediatek,mt8183-dsi",
> > > +         .data = &mt8183_dsi_driver_data },
> > >         { },
> > >  };
> > >
> > > --
> > > 2.20.1
> > >
>
>