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@intel.com
Signed-off-by: Joy Chakraborty <joychakr@google.com
Reviewed-by: Serge Semin <fancer.lancer@gmail.com
Tested-by: Serge Semin <fancer.lancer@gmail.com
Link: https://lore.kernel.org/r/20230512104746.1797865-4-joychakr@google.com
Signed-off-by: Mark Brown <broonie@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index c3bfb6c..4976e3b 100644 (file)
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -426,7 +426,10 @@ 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;