If the device-tree specifies a max-memory-bandwidth property then
the CLCD driver uses that to calculate the bits-per-pixel supported,
however, it doesn't ensure that the result is a sane value, i.e. a
power of 2 and <= 32 as the rest of the code assumes.
Acked-by: Pawel Moll <pawel.moll@xxxxxxx>
Signed-off-by: Jon Medhurst <tixy@xxxxxxxxxx>
---
This fixes code which is new in 3.17 (commit d10715be03) and so I assume
is a candidate for adding to a coming -rc ? Without the fix, people can
be left (as I was) with a blank non-functioning screen even if they
create a valid device-tree for the new driver functionality.
drivers/video/fbdev/amba-clcd.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/video/fbdev/amba-clcd.c b/drivers/video/fbdev/amba-clcd.c
index beadd3e..98b66b7 100644
--- a/drivers/video/fbdev/amba-clcd.c
+++ b/drivers/video/fbdev/amba-clcd.c
@@ -24,6 +24,7 @@
#include <linux/list.h>
#include <linux/amba/bus.h>
#include <linux/amba/clcd.h>
+#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/hardirq.h>
#include <linux/dma-mapping.h>
@@ -650,6 +651,7 @@ static int clcdfb_of_init_display(struct clcd_fb *fb)
{
struct device_node *endpoint;
int err;
+ int bpp;
u32 max_bandwidth;
u32 tft_r0b0g0[3];
@@ -667,11 +669,15 @@ static int clcdfb_of_init_display(struct clcd_fb *fb)
err = of_property_read_u32(fb->dev->dev.of_node, "max-memory-bandwidth",
&max_bandwidth);
- if (!err)
- fb->panel->bpp = 8 * max_bandwidth / (fb->panel->mode.xres *
+ if (!err) {
+ bpp = 8 * max_bandwidth / (fb->panel->mode.xres *
fb->panel->mode.yres * fb->panel->mode.refresh);
- else
- fb->panel->bpp = 32;
+ bpp = rounddown_pow_of_two(bpp);
+ if (bpp > 32)
+ bpp = 32;
+ } else
+ bpp = 32;
+ fb->panel->bpp = bpp;
#ifdef CONFIG_CPU_BIG_ENDIAN
fb->panel->cntl |= CNTL_BEBO;
--
2.0.1
--
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