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

[Thierry Reding]

On Mon, Jul 20, 2015 at 02:39:36AM -0500, Steev Klimaszewski wrote:
> 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>

Great, thanks.

Thierry
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