From: Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx>
(cherry picked from upstream af0e6242909c3c4297392ca3e94eff1b4db71a97)
Taking one interrupt for every byte is rather slow. Since the
controller is perfectly capable of transmitting 32 bits at a time,
change t->bits_per-word to 32 when the length is divisible by 4 and
large enough that the reduced number of interrupts easily compensates
for the one or two extra fsl_spi_setup_transfer() calls this causes.
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
drivers/spi/spi-fsl-spi.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 479d10dc6cb8..946b417f2d1c 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -357,12 +357,28 @@ static int fsl_spi_bufs(struct spi_device *spi, struct spi_transfer *t,
static int fsl_spi_do_one_msg(struct spi_master *master,
struct spi_message *m)
{
+ struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(master);
struct spi_device *spi = m->spi;
struct spi_transfer *t, *first;
unsigned int cs_change;
const int nsecs = 50;
int status;
+ /*
+ * In CPU mode, optimize large byte transfers to use larger
+ * bits_per_word values to reduce number of interrupts taken.
+ */
+ if (!(mpc8xxx_spi->flags & SPI_CPM_MODE)) {
+ list_for_each_entry(t, &m->transfers, transfer_list) {
+ if (t->len < 256 || t->bits_per_word != 8)
+ continue;
+ if ((t->len & 3) == 0)
+ t->bits_per_word = 32;
+ else if ((t->len & 1) == 0)
+ t->bits_per_word = 16;
+ }
+ }
+
/* Don't allow changes if CS is active */
first = list_first_entry(&m->transfers, struct spi_transfer,
transfer_list);
--
2.40.1
