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

[Thierry Reding]

From: Thierry Reding <tred...@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