This is a note to let you know that I've just added the patch titled
spi: dw: Fix detecting FIFO depth
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
spi-dw-fix-detecting-fifo-depth.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d297933cc7fcfbaaf2d37570baac73287bf0357d Mon Sep 17 00:00:00 2001
From: Axel Lin <axel.lin@xxxxxxxxxx>
Date: Mon, 5 Jan 2015 09:32:56 +0800
Subject: spi: dw: Fix detecting FIFO depth
From: Axel Lin <axel.lin@xxxxxxxxxx>
commit d297933cc7fcfbaaf2d37570baac73287bf0357d upstream.
Current code tries to find the highest valid fifo depth by checking the value
it wrote to DW_SPI_TXFLTR. There are a few problems in current code:
1) There is an off-by-one in dws->fifo_len setting because it assumes the latest
register write fails so the latest valid value should be fifo - 1.
2) We know the depth could be from 2 to 256 from HW spec, so it is not necessary
to test fifo == 257. In the case fifo is 257, it means the latest valid
setting is fifo = 256. So after the for loop iteration, we should check
fifo == 2 case instead of fifo == 257 if detecting the FIFO depth fails.
This patch fixes above issues.
Signed-off-by: Axel Lin <axel.lin@xxxxxxxxxx>
Reviewed-and-tested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/spi/spi-dw.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -621,13 +621,13 @@ static void spi_hw_init(struct dw_spi *d
if (!dws->fifo_len) {
u32 fifo;
- for (fifo = 2; fifo <= 257; fifo++) {
+ for (fifo = 2; fifo <= 256; fifo++) {
dw_writew(dws, DW_SPI_TXFLTR, fifo);
if (fifo != dw_readw(dws, DW_SPI_TXFLTR))
break;
}
- dws->fifo_len = (fifo == 257) ? 0 : fifo;
+ dws->fifo_len = (fifo == 2) ? 0 : fifo - 1;
dw_writew(dws, DW_SPI_TXFLTR, 0);
}
}
Patches currently in stable-queue which might be from axel.lin@xxxxxxxxxx are
queue-3.18/spi-dw-fix-detecting-fifo-depth.patch
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