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From:   Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Date:   Mon, 23 Dec 2019 06:58:32 -0700
Message-ID: <CAOCk7NoDsjGWV=ddZO2yVG_n2N-mhdhfeaNML=kTTr2Mg88q0Q@mail.gmail.com>
Subject: Re: [Freedreno] [v1] drm/msm: update LANE_CTRL register value from
 default value
To:     Harigovindan P <harigovi@codeaurora.org>
Cc:     "open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
        MSM <linux-arm-msm@vger.kernel.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        DTML <devicetree@vger.kernel.org>,
        Abhinav Kumar <abhinavk@codeaurora.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Rob Clark <robdclark@gmail.com>, nganji@codeaurora.org,
        Sean Paul <seanpaul@chromium.org>,
        "Kristian H. Kristensen" <hoegsberg@chromium.org>,
        Jeykumar Sankaran <jsanka@codeaurora.org>,
        Chandan Uddaraju <chandanu@codeaurora.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Dec 23, 2019 at 3:19 AM Harigovindan P <harigovi@codeaurora.org> wrote:
>
> Updating REG_DSI_LANE_CTRL register value by reading default
> register value and writing it back using bitwise OR with
> DSI_LANE_CTRL_CLKLN_HS_FORCE_REQUEST. This works for all panels.

Why?
You explain what the code does, which I can tell from reading the
code.  The commit text should tell me why this change is necessary.
Why would I care if this change is in my tree or not?  What feature
does it provide or what issue does it fix?

>
> Signed-off-by: Harigovindan P <harigovi@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index e6289a3..d3c5233 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -816,7 +816,7 @@ static void dsi_ctrl_config(struct msm_dsi_host *msm_host, bool enable,
>         u32 flags = msm_host->mode_flags;
>         enum mipi_dsi_pixel_format mipi_fmt = msm_host->format;
>         const struct msm_dsi_cfg_handler *cfg_hnd = msm_host->cfg_hnd;
> -       u32 data = 0;
> +       u32 data = 0, lane_ctrl = 0;
>
>         if (!enable) {
>                 dsi_write(msm_host, REG_DSI_CTRL, 0);
> @@ -904,9 +904,11 @@ static void dsi_ctrl_config(struct msm_dsi_host *msm_host, bool enable,
>         dsi_write(msm_host, REG_DSI_LANE_SWAP_CTRL,
>                   DSI_LANE_SWAP_CTRL_DLN_SWAP_SEL(msm_host->dlane_swap));
>
> -       if (!(flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
> +       if (!(flags & MIPI_DSI_CLOCK_NON_CONTINUOUS)) {
> +               lane_ctrl = dsi_read(msm_host, REG_DSI_LANE_CTRL);
>                 dsi_write(msm_host, REG_DSI_LANE_CTRL,
> -                       DSI_LANE_CTRL_CLKLN_HS_FORCE_REQUEST);
> +                       lane_ctrl | DSI_LANE_CTRL_CLKLN_HS_FORCE_REQUEST);
> +       }
>
>         data |= DSI_CTRL_ENABLE;
>
> --
> 2.7.4
>
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