Re: [RFC PATCH v3 7/7] drm: exynos: mixer: Add interconnect support

[Chanwoo Choi]

Hi,

On Fri, Dec 20, 2019 at 9:03 PM Artur ÅwigoÅ <a.swigon@xxxxxxxxxxx> wrote:
>
> From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> This patch adds interconnect support to exynos-mixer. The mixer works
> the same as before when CONFIG_INTERCONNECT is 'n'.

The patch description doesn't include why interconnect is required
and what to do.

>
> Co-developed-by: Artur ÅwigoÅ <a.swigon@xxxxxxxxxxx>
> Signed-off-by: Artur ÅwigoÅ <a.swigon@xxxxxxxxxxx>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/exynos/exynos_mixer.c | 71 +++++++++++++++++++++++++--
>  1 file changed, 66 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
> index 6cfdb95fef2f..a7e7240a055f 100644
> --- a/drivers/gpu/drm/exynos/exynos_mixer.c
> +++ b/drivers/gpu/drm/exynos/exynos_mixer.c
> @@ -13,6 +13,7 @@
>  #include <linux/component.h>
>  #include <linux/delay.h>
>  #include <linux/i2c.h>
> +#include <linux/interconnect.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
>  #include <linux/kernel.h>
> @@ -97,6 +98,7 @@ struct mixer_context {
>         struct exynos_drm_crtc  *crtc;
>         struct exynos_drm_plane planes[MIXER_WIN_NR];
>         unsigned long           flags;
> +       struct icc_path         *soc_path;
>
>         int                     irq;
>         void __iomem            *mixer_regs;
> @@ -931,6 +933,40 @@ static void mixer_disable_vblank(struct exynos_drm_crtc *crtc)
>         mixer_reg_writemask(mixer_ctx, MXR_INT_EN, 0, MXR_INT_EN_VSYNC);
>  }
>
> +static void mixer_set_memory_bandwidth(struct exynos_drm_crtc *crtc)
> +{
> +       struct drm_display_mode *mode = &crtc->base.state->adjusted_mode;
> +       struct mixer_context *ctx = crtc->ctx;
> +       unsigned long bw, bandwidth = 0;
> +       int i, j, sub;
> +
> +       if (!ctx->soc_path)
> +               return;
> +
> +       for (i = 0; i < MIXER_WIN_NR; i++) {
> +               struct drm_plane *plane = &ctx->planes[i].base;
> +               const struct drm_format_info *format;
> +
> +               if (plane->state && plane->state->crtc && plane->state->fb) {
> +                       format = plane->state->fb->format;
> +                       bw = mode->hdisplay * mode->vdisplay *
> +                                                       drm_mode_vrefresh(mode);
> +                       if (mode->flags & DRM_MODE_FLAG_INTERLACE)
> +                               bw /= 2;
> +                       for (j = 0; j < format->num_planes; j++) {
> +                               sub = j ? (format->vsub * format->hsub) : 1;
> +                               bandwidth += format->cpp[j] * bw / sub;
> +                       }
> +               }
> +       }
> +
> +       /* add 20% safety margin */
> +       bandwidth = bandwidth / 4 * 5;
> +
> +       dev_dbg(ctx->dev, "exynos-mixer: safe bandwidth %ld Bps\n", bandwidth);
> +       icc_set_bw(ctx->soc_path, Bps_to_icc(bandwidth), 0);
> +}

I recommend that add the role of this function in order to guarantee
the minimum bandwidth to prevent performance drop or h/w issue.

> +
>  static void mixer_atomic_begin(struct exynos_drm_crtc *crtc)
>  {
>         struct mixer_context *ctx = crtc->ctx;
> @@ -982,6 +1018,7 @@ static void mixer_atomic_flush(struct exynos_drm_crtc *crtc)
>         if (!test_bit(MXR_BIT_POWERED, &mixer_ctx->flags))
>                 return;
>
> +       mixer_set_memory_bandwidth(crtc);
>         mixer_enable_sync(mixer_ctx);
>         exynos_crtc_handle_event(crtc);
>  }
> @@ -1029,6 +1066,7 @@ static void mixer_disable(struct exynos_drm_crtc *crtc)
>         for (i = 0; i < MIXER_WIN_NR; i++)
>                 mixer_disable_plane(crtc, &ctx->planes[i]);
>
> +       mixer_set_memory_bandwidth(crtc);
>         exynos_drm_pipe_clk_enable(crtc, false);
>
>         pm_runtime_put(ctx->dev);
> @@ -1220,12 +1258,22 @@ static int mixer_probe(struct platform_device *pdev)
>         struct device *dev = &pdev->dev;
>         const struct mixer_drv_data *drv;
>         struct mixer_context *ctx;
> +       struct icc_path *path;
>         int ret;
>
> +       /*
> +        * Returns NULL if CONFIG_INTERCONNECT is disabled.
> +        * May return ERR_PTR(-EPROBE_DEFER).
> +        */
> +       path = of_icc_get(dev, NULL);
> +       if (IS_ERR(path))
> +               return PTR_ERR(path);
> +
>         ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
>         if (!ctx) {
>                 DRM_DEV_ERROR(dev, "failed to alloc mixer context.\n");
> -               return -ENOMEM;
> +               ret = -ENOMEM;
> +               goto err;
>         }
>
>         drv = of_device_get_match_data(dev);
> @@ -1233,6 +1281,7 @@ static int mixer_probe(struct platform_device *pdev)
>         ctx->pdev = pdev;
>         ctx->dev = dev;
>         ctx->mxr_ver = drv->version;
> +       ctx->soc_path = path;
>
>         if (drv->is_vp_enabled)
>                 __set_bit(MXR_BIT_VP_ENABLED, &ctx->flags);
> @@ -1242,17 +1291,29 @@ static int mixer_probe(struct platform_device *pdev)
>         platform_set_drvdata(pdev, ctx);
>
>         ret = component_add(&pdev->dev, &mixer_component_ops);
> -       if (!ret)
> -               pm_runtime_enable(dev);
> +       if (ret < 0)
> +               goto err;
> +
> +       pm_runtime_enable(dev);
> +
> +       return 0;
> +
> +err:
> +       icc_put(path);
>
>         return ret;
>  }
>
>  static int mixer_remove(struct platform_device *pdev)
>  {
> -       pm_runtime_disable(&pdev->dev);
> +       struct device *dev = &pdev->dev;
> +       struct mixer_context *ctx = dev_get_drvdata(dev);
> +
> +       pm_runtime_disable(dev);
> +
> +       component_del(dev, &mixer_component_ops);
>
> -       component_del(&pdev->dev, &mixer_component_ops);
> +       icc_put(ctx->soc_path);
>
>         return 0;
>  }
> --
> 2.17.1
>

Basically, I agree this patch about using ICC feature
to guarantee the minimum bandwidth. But, I don't have
the knowledge of exynos-mixer.c. So, just I reviewed
the part of ICC usage. After digging the exynos-mixer.c,
I'll reply the reviewed tag. Thanks.

-- 
Best Regards,
Chanwoo Choi