Date:   Fri, 15 Mar 2019 11:26:43 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Yongqiang Niu <yongqiang.niu@...iatek.com>
Cc:     CK Hu <ck.hu@...iatek.com>, Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        devicetree@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 10/18] drm/mediatek: add gmc_bits for ovl private data

On Fri, Mar 15, 2019 at 10:34 AM Yongqiang Niu
<yongqiang.niu@...iatek.com> wrote:
>
> On Tue, 2018-12-25 at 12:15 +0800, Nicolas Boichat wrote:
> > On Mon, Dec 24, 2018 at 6:53 PM Yongqiang Niu
> > <yongqiang.niu@...iatek.com> wrote:
> > >
> > > This patch add gmc_bits for ovl private data
> > >
> > > Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 23 +++++++++++++++++++++--
> > >  1 file changed, 21 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > > index 28d1911..afb313c 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> > > @@ -39,7 +39,9 @@
> > >  #define DISP_REG_OVL_ADDR_MT8173               0x0f40
> > >  #define DISP_REG_OVL_ADDR(ovl, n)              ((ovl)->data->addr + 0x20 * (n))
> > >
> > > -#define        OVL_RDMA_MEM_GMC        0x40402020
> > > +#define GMC_THRESHOLD_BITS     16
> > > +#define GMC_THRESHOLD_HIGH     ((1 << GMC_THRESHOLD_BITS) / 4)
> > > +#define GMC_THRESHOLD_LOW      ((1 << GMC_THRESHOLD_BITS) / 8)
> > >
> > >  #define OVL_CON_BYTE_SWAP      BIT(24)
> > >  #define OVL_CON_MTX_YUV_TO_RGB (6 << 16)
> > > @@ -57,6 +59,7 @@
> > >
> > >  struct mtk_disp_ovl_data {
> > >         unsigned int addr;
> > > +       unsigned int gmc_bits;
> > >         bool fmt_rgb565_is_0;
> > >  };
> > >
> > > @@ -140,9 +143,23 @@ static unsigned int mtk_ovl_layer_nr(struct mtk_ddp_comp *comp)
> > >  static void mtk_ovl_layer_on(struct mtk_ddp_comp *comp, unsigned int idx)
> > >  {
> > >         unsigned int reg;
> > > +       unsigned int gmc_thrshd_l;
> > > +       unsigned int gmc_thrshd_h;
> > > +       unsigned int gmc_value;
> > > +       struct mtk_disp_ovl *ovl = comp_to_ovl(comp);
> > >
> > >         writel(0x1, comp->regs + DISP_REG_OVL_RDMA_CTRL(idx));
> > > -       writel(OVL_RDMA_MEM_GMC, comp->regs + DISP_REG_OVL_RDMA_GMC(idx));
> > > +
> > > +       gmc_thrshd_l = GMC_THRESHOLD_LOW >>
> > > +                     (GMC_THRESHOLD_BITS - ovl->data->gmc_bits);
> > > +       gmc_thrshd_h = GMC_THRESHOLD_HIGH >>
> > > +                     (GMC_THRESHOLD_BITS - ovl->data->gmc_bits);
> > > +       if (ovl->data->gmc_bits == 10)
> > > +               gmc_value = gmc_thrshd_h | gmc_thrshd_h << 16;
> >
> > I don't really get what this does, but is it intentional that you
> > don't use gmc_thrshd_l here?
> >
> GMC register was set RDMA ultra and pre-ultra threshold.
> MT8183 GMC register define is different with other SOC, gmc_thrshd_l not
> used here.

Ok cool. My issue is that this really appears to be like a mistake, so
maybe it's better to only compute gmc_thrshd_l in the else branch?

gmc_thrshd_h = GMC_THRESHOLD_HIGH >>
                     (GMC_THRESHOLD_BITS - ovl->data->gmc_bits);
if (ovl->data->gmc_bits == 10) {
     gmc_value = gmc_thrshd_h | gmc_thrshd_h << 16;
} else {
     gmc_thrshd_l = GMC_THRESHOLD_LOW >>
                     (GMC_THRESHOLD_BITS - ovl->data->gmc_bits);
     gmc_value = gmc_thrshd_l | gmc_thrshd_l << 8 |
                          gmc_thrshd_h << 16 | gmc_thrshd_h << 24;
}

> > Also, if you only ever use 8 or 10 bits gmc, maybe it's easier to
> > hard-code the 2 values?
> > if (ovl->data->gmc_bits == 10)
> >   gmc_value = OVL_RDMA_MEM_GMC_10BIT;
> > else
> >   gmc_value = OVL_RDMA_MEM_GMC_8BIT; //0x40402020
> >
>
> our internal maintainer prefer calculate GMC setting with private data
> gmc bit instead of hard-core.
> and with calculation function that will be more flexible

Sounds ok.

> > > +       else
> > > +               gmc_value = gmc_thrshd_l | gmc_thrshd_l << 8 |
> > > +                           gmc_thrshd_h << 16 | gmc_thrshd_h << 24;
> > > +       writel(gmc_value, comp->regs + DISP_REG_OVL_RDMA_GMC(idx));
> > >
> > >         reg = readl(comp->regs + DISP_REG_OVL_SRC_CON);
> > >         reg = reg | BIT(idx);
> > > @@ -324,11 +341,13 @@ static int mtk_disp_ovl_remove(struct platform_device *pdev)
> > >
> > >  static const struct mtk_disp_ovl_data mt2701_ovl_driver_data = {
> > >         .addr = DISP_REG_OVL_ADDR_MT2701,
> > > +       .gmc_bits = 8,
> > >         .fmt_rgb565_is_0 = false,
> > >  };
> > >
> > >  static const struct mtk_disp_ovl_data mt8173_ovl_driver_data = {
> > >         .addr = DISP_REG_OVL_ADDR_MT8173,
> > > +       .gmc_bits = 8,
> > >         .fmt_rgb565_is_0 = true,
> > >  };
> > >
> > > --
> > > 1.8.1.1.dirty
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@...ts.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>

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