From: Rasmus Villemoes rasmus.villemoes@prevas.dk
(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@prevas.dk Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/spi/spi-fsl-spi.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- 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_devic 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);