[v2] bus: sunxi-rsb: Return correct data when mixing 16-bit and 8-bit reads

Commit Message

Ondřej Jirman Feb. 21, 2020, 8:27 p.m. UTC

When doing a 16-bit read that returns data in the MSB byte, the
RSB_DATA register will keep the MSB byte unchanged when doing
the following 8-bit read. sunxi_rsb_read() will then return
a result that contains high byte from 16-bit read mixed with
the 8-bit result.

The consequence is that after this happens the PMIC's regmap will
look like this: (0x33 is the high byte from the 16-bit read)

% cat /sys/kernel/debug/regmap/sunxi-rsb-3a3/registers
00: 33
01: 33
02: 33
03: 33
04: 33
05: 33
06: 33
07: 33
08: 33
09: 33
0a: 33
0b: 33
0c: 33
0d: 33
0e: 33
[snip]

Fix this by masking the result of the read with the correct mask
based on the size of the read. There are no 16-bit users in the
mainline kernel, so this doesn't need to get into the stable tree.

Signed-off-by: Ondrej Jirman <[e-mail]>
Acked-by: Chen-Yu Tsai <[e-mail]>
---
 drivers/bus/sunxi-rsb.c | 1 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Maxime Ripard Feb. 24, 2020, 11:02 a.m. UTC | #1

On Fri, Feb 21, 2020 at 09:27:26PM +0100, Ondrej Jirman wrote:
> When doing a 16-bit read that returns data in the MSB byte, the
> RSB_DATA register will keep the MSB byte unchanged when doing
> the following 8-bit read. sunxi_rsb_read() will then return
> a result that contains high byte from 16-bit read mixed with
> the 8-bit result.
>
> The consequence is that after this happens the PMIC's regmap will
> look like this: (0x33 is the high byte from the 16-bit read)
>
> % cat /sys/kernel/debug/regmap/sunxi-rsb-3a3/registers
> 00: 33
> 01: 33
> 02: 33
> 03: 33
> 04: 33
> 05: 33
> 06: 33
> 07: 33
> 08: 33
> 09: 33
> 0a: 33
> 0b: 33
> 0c: 33
> 0d: 33
> 0e: 33
> [snip]
>
> Fix this by masking the result of the read with the correct mask
> based on the size of the read. There are no 16-bit users in the
> mainline kernel, so this doesn't need to get into the stable tree.
>
> Signed-off-by: Ondrej Jirman <[e-mail]>
> Acked-by: Chen-Yu Tsai <[e-mail]>

Applied, thanks!
Maxime

Patch

diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
index b8043b58568ac..8ab6a3865f569 100644
--- a/drivers/bus/sunxi-rsb.c
+++ b/drivers/bus/sunxi-rsb.c
@@ -345,7 +349,7 @@  static int sunxi_rsb_read(struct sunxi_rsb *rsb, u8 rtaddr, u8 addr,
 	if (ret)
 		goto unlock;
 
-	*buf = readl(rsb->regs + RSB_DATA);
+	*buf = readl(rsb->regs + RSB_DATA) & GENMASK(len * 8 - 1, 0);
 
 unlock:
 	mutex_unlock(&rsb->lock);