Patch "spi: dw: Round of n_bytes to power of 2" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    spi: dw: Round of n_bytes to power of 2

to the 5.15-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-round-of-n_bytes-to-power-of-2.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 70259d0ff6639d1bf2cf955b63941b261ea32650
Author: Joy Chakraborty <joychakr@xxxxxxxxxx>
Date:   Fri May 12 10:47:45 2023 +0000

    spi: dw: Round of n_bytes to power of 2
    
    [ Upstream commit 9f34baf67e4d08908fd94ff29c825bb673295336 ]
    
    n_bytes variable in the driver represents the number of bytes per word
    that needs to be sent/copied to fifo. Bits/word can be between 8 and 32
    bits from the client but in memory they are a power of 2, same is mentioned
    in spi.h header:
    "
     * @bits_per_word: Data transfers involve one or more words; word sizes
     *      like eight or 12 bits are common.  In-memory wordsizes are
     *      powers of two bytes (e.g. 20 bit samples use 32 bits).
     *      This may be changed by the device's driver, or left at the
     *      default (0) indicating protocol words are eight bit bytes.
     *      The spi_transfer.bits_per_word can override this for each transfer.
    "
    
    Hence, round of n_bytes to a power of 2 to avoid values like 3 which
    would generate unalligned/odd accesses to memory/fifo.
    
    * tested on Baikal-T1 based system with DW SPI-looped back interface
    transferring a chunk of data with DFS:8,12,16.
    
    Fixes: a51acc2400d4 ("spi: dw: Add support for 32-bits max xfer size")
    Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx
    Signed-off-by: Joy Chakraborty <joychakr@xxxxxxxxxx
    Reviewed-by: Serge Semin <fancer.lancer@xxxxxxxxx
    Tested-by: Serge Semin <fancer.lancer@xxxxxxxxx
    Link: https://lore.kernel.org/r/20230512104746.1797865-4-joychakr@xxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 59e22c6b4b201..8fc598f09a728 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -416,7 +416,10 @@ static int dw_spi_transfer_one(struct spi_controller *master,
 	int ret;
 
 	dws->dma_mapped = 0;
-	dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
+	dws->n_bytes =
+		roundup_pow_of_two(DIV_ROUND_UP(transfer->bits_per_word,
+						BITS_PER_BYTE));
+
 	dws->tx = (void *)transfer->tx_buf;
 	dws->tx_len = transfer->len / dws->n_bytes;
 	dws->rx = transfer->rx_buf;