[PATCH 4/8] drm/exynos: fimd: clear channel before enabling iommu

[Stéphane Marchesin]

On Wed, Dec 26, 2012 at 3:27 AM, Prathyush K <prathyush.k at samsung.com> wrote:
> From: Akshu Agrawal <akshu.a at samsung.com>
>
> If any fimd channel was already active, initializing iommu will result
> in a PAGE FAULT (e.g. u-boot could have turned on the display and
> not disabled it before the kernel starts). This patch checks if any
> channel is active before initializing iommu and disables it.
>

Will that work if another drm exynos platform driver (let's say hdmi)
starts before fimd and enables the iommu?

Stéphane

> Signed-off-by: Akshu Agrawal <akshu.a at samsung.com>
> Signed-off-by: Prathyush K <prathyush.k at samsung.com>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_fimd.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> index f88eaa4..3aeedf5 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> @@ -733,6 +733,28 @@ out:
>         return IRQ_HANDLED;
>  }
>
> +static void fimd_clear_channel(struct device *dev)
> +{
> +       struct fimd_context *ctx = get_fimd_context(dev);
> +       int win, ch_enabled = 0;
> +
> +       DRM_DEBUG_KMS("%s\n", __FILE__);
> +
> +       /* Check if any channel is enabled */
> +       for (win = 0; win < WINDOWS_NR; win++) {
> +               u32 val = readl(ctx->regs + SHADOWCON);
> +               if (val & SHADOWCON_CHx_ENABLE(win)) {
> +                       val &= ~SHADOWCON_CHx_ENABLE(win);
> +                       writel(val, ctx->regs + SHADOWCON);
> +                       ch_enabled = 1;
> +               }
> +       }
> +
> +       /* Wait for vsync, as disable channel takes effect at next vsync */
> +       if (ch_enabled)
> +               fimd_wait_for_vblank(dev);
> +}
> +
>  static int fimd_subdrv_probe(struct drm_device *drm_dev, struct device *dev)
>  {
>         DRM_DEBUG_KMS("%s\n", __FILE__);
> @@ -755,9 +777,14 @@ static int fimd_subdrv_probe(struct drm_device *drm_dev, struct device *dev)
>         drm_dev->vblank_disable_allowed = 1;
>
>         /* attach this sub driver to iommu mapping if supported. */
> -       if (is_drm_iommu_supported(drm_dev))
> +       if (is_drm_iommu_supported(drm_dev)) {
> +               /*
> +                * If any channel is already active, iommu will throw
> +                * a PAGE FAULT when enabled. So clear any channel if enabled.
> +                */
> +               fimd_clear_channel(dev);
>                 drm_iommu_attach_device(drm_dev, dev);
> -
> +       }
>         return 0;
>  }
>
> --
> 1.8.0
>
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