Eric Lee / smarc-ti-linux-kernel

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Commit 128e53423c64343f4974fbcb29758a86a40dad35

Authored by Axel Lin
Committed by Greg Kroah-Hartman
1 parent 179ac907a2

spi: dw: Fix detecting FIFO depth 

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@ingics.com>
Reviewed-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Showing 1 changed file with 2 additions and 2 deletions Side-by-side Diff

drivers/spi/spi-dw.c
Diff comments   View file @ 128e534
... ... @@ -621,13 +621,13 @@
621 621 if (!dws->fifo_len) {
622 622 u32 fifo;
623 623  
624   - for (fifo = 2; fifo <= 257; fifo++) {
  624 + for (fifo = 2; fifo <= 256; fifo++) {
625 625 dw_writew(dws, DW_SPI_TXFLTR, fifo);
626 626 if (fifo != dw_readw(dws, DW_SPI_TXFLTR))
627 627 break;
628 628 }
629 629  
630   - dws->fifo_len = (fifo == 257) ? 0 : fifo;
  630 + dws->fifo_len = (fifo == 2) ? 0 : fifo - 1;
631 631 dw_writew(dws, DW_SPI_TXFLTR, 0);
632 632 }
633 633 }