[PATCH] drm/tegra: dpaux: Fix transfers larger than 4 bytes

[Steev Klimaszewski]

On Mon, Jul 20, 2015 at 1:49 AM, Thierry Reding <thierry.reding at gmail.com>
wrote:

> From: Thierry Reding <treding at nvidia.com>
>
> The DPAUX read/write FIFO registers aren't sequential in the register
> space, causing transfers larger than 4 bytes to cause accesses to non-
> existing FIFO registers.
>
> Fixes: 6b6b604215c6 ("drm/tegra: Add eDP support")
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/tegra/dpaux.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
> index d6b55e3e3716..a43a836e6f88 100644
> --- a/drivers/gpu/drm/tegra/dpaux.c
> +++ b/drivers/gpu/drm/tegra/dpaux.c
> @@ -72,34 +72,32 @@ static inline void tegra_dpaux_writel(struct
> tegra_dpaux *dpaux,
>  static void tegra_dpaux_write_fifo(struct tegra_dpaux *dpaux, const u8
> *buffer,
>                                    size_t size)
>  {
> -       unsigned long offset = DPAUX_DP_AUXDATA_WRITE(0);
>         size_t i, j;
>
> -       for (i = 0; i < size; i += 4) {
> -               size_t num = min_t(size_t, size - i, 4);
> +       for (i = 0; i < DIV_ROUND_UP(size, 4); i++) {
> +               size_t num = min_t(size_t, size - i * 4, 4);
>                 unsigned long value = 0;
>
>                 for (j = 0; j < num; j++)
> -                       value |= buffer[i + j] << (j * 8);
> +                       value |= buffer[i * 4 + j] << (j * 8);
>
> -               tegra_dpaux_writel(dpaux, value, offset++);
> +               tegra_dpaux_writel(dpaux, value,
> DPAUX_DP_AUXDATA_WRITE(i));
>         }
>  }
>
>  static void tegra_dpaux_read_fifo(struct tegra_dpaux *dpaux, u8 *buffer,
>                                   size_t size)
>  {
> -       unsigned long offset = DPAUX_DP_AUXDATA_READ(0);
>         size_t i, j;
>
> -       for (i = 0; i < size; i += 4) {
> -               size_t num = min_t(size_t, size - i, 4);
> +       for (i = 0; i < DIV_ROUND_UP(size, 4); i++) {
> +               size_t num = min_t(size_t, size - i * 4, 4);
>                 unsigned long value;
>
> -               value = tegra_dpaux_readl(dpaux, offset++);
> +               value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXDATA_READ(i));
>
>                 for (j = 0; j < num; j++)
> -                       buffer[i + j] = value >> (j * 8);
> +                       buffer[i * 4 + j] = value >> (j * 8);
>         }
>  }
>
> --
> 2.4.5
>
>

This fixes the issue that I reported earlier, so feel free to add my

Tested-by: Steev Klimaszewski <steev at gentoo.org>
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