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authorRasmus Villemoes <rasmus.villemoes@prevas.dk>2019-03-27 17:30:52 +0300
committerMark Brown <broonie@kernel.org>2019-04-02 09:01:15 +0300
commitaf0e6242909c3c4297392ca3e94eff1b4db71a97 (patch)
tree4ae786fa15f6de09bdef58c4566c737da62527ea /drivers/spi/spi-fsl-spi.c
parenta798a7086c38d91d304132c194cff9f02197f5cd (diff)
downloadlinux-af0e6242909c3c4297392ca3e94eff1b4db71a97.tar.xz
spi: spi-fsl-spi: automatically adapt bits-per-word in cpu mode
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@prevas.dk> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-fsl-spi.c')
-rw-r--r--drivers/spi/spi-fsl-spi.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index e2b341943796..b36ac6aa3b1f 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -363,12 +363,28 @@ 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, last_bpw;
+ /*
+ * 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 */
cs_change = 1;
list_for_each_entry(t, &m->transfers, transfer_list) {