linux-kernel - Re: [PATCH 03/18] drm/mediatek: redefine mtk_ddp_sout_sel

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Date:   Tue, 25 Dec 2018 11:57:00 +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,
        linux-mediatek@...ts.infradead.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 03/18] drm/mediatek: redefine mtk_ddp_sout_sel

On Mon, Dec 24, 2018 at 6:52 PM Yongqiang Niu
<yongqiang.niu@...iatek.com> wrote:
>
> This patch redefine mtk_ddp_sout_sel

Can you describe a bit more why you are making this change?

> Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_ddp.c | 32 ++++++++++++++++++++------------
>  1 file changed, 20 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> index adb37e4..592f852 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> @@ -405,21 +405,27 @@ static unsigned int mtk_ddp_sel_in(enum mtk_ddp_comp_id cur,
>         return value;
>  }
>
> -static void mtk_ddp_sout_sel(void __iomem *config_regs,
> -                            enum mtk_ddp_comp_id cur,
> -                            enum mtk_ddp_comp_id next)
> +static unsigned int mtk_ddp_sout_sel(void __iomem *config_regs,

You don't use config_regs anymore, drop it.

> +                                    enum mtk_ddp_comp_id cur,
> +                                    enum mtk_ddp_comp_id next,
> +                                    unsigned int *addr)
>  {
> +       unsigned int value;
> +
>         if (cur == DDP_COMPONENT_BLS && next == DDP_COMPONENT_DSI0) {
> -               writel_relaxed(BLS_TO_DSI_RDMA1_TO_DPI1,
> -                              config_regs + DISP_REG_CONFIG_OUT_SEL);
> +               *addr = DISP_REG_CONFIG_OUT_SEL;
> +               value = BLS_TO_DSI_RDMA1_TO_DPI1;

You can directly return BLS_TO_DSI_RDMA1_TO_DPI1.

>         } else if (cur == DDP_COMPONENT_BLS && next == DDP_COMPONENT_DPI0) {
> -               writel_relaxed(BLS_TO_DPI_RDMA1_TO_DSI,
> -                              config_regs + DISP_REG_CONFIG_OUT_SEL);
> -               writel_relaxed(DSI_SEL_IN_RDMA,
> -                              config_regs + DISP_REG_CONFIG_DSI_SEL);
> -               writel_relaxed(DPI_SEL_IN_BLS,
> -                              config_regs + DISP_REG_CONFIG_DPI_SEL);
> +               *addr = DISP_REG_CONFIG_OUT_SEL;
> +               value = BLS_TO_DPI_RDMA1_TO_DSI;

I (kind of) understand the change above, as you still end up writing
BLS_TO_DSI_RDMA1_TO_DPI1 in DISP_REG_CONFIG_OUT_SEL.

This changes the behaviour, as now you only write
BLS_TO_DPI_RDMA1_TO_DSI to DISP_REG_CONFIG_OUT_SEL, but the previous
revision of the code would also write to DISP_REG_CONFIG_DSI_SEL and
DISP_REG_CONFIG_DPI_SEL. Why?

> +       } else if (cur == DDP_COMPONENT_RDMA1 && next == DDP_COMPONENT_DSI0) {
> +               *addr = DISP_REG_CONFIG_DSI_SEL;
> +               value = DSI_SEL_IN_RDMA;
> +       } else {
> +               value = 0;
>         }
> +
> +       return value;
>  }
>
>  void mtk_ddp_add_comp_to_path(void __iomem *config_regs,
> @@ -434,7 +440,9 @@ void mtk_ddp_add_comp_to_path(void __iomem *config_regs,
>                 writel_relaxed(reg, config_regs + addr);
>         }
>
> -       mtk_ddp_sout_sel(config_regs, cur, next);
> +       value = mtk_ddp_sout_sel(cur, next, &addr);
> +       if (value)
> +               writel_relaxed(value, config_regs + addr);

Why this change? I don't see mtk_ddp_sout_sel being used later in the
series, so I'm not sure why we don't directly write the value into the
register.

>         value = mtk_ddp_sel_in(cur, next, &addr);
>         if (value) {
> --
> 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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