diff options
| author | Rasmus Villemoes <rasmus.villemoes@prevas.dk> | 2019-03-27 17:30:52 +0300 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2019-04-02 09:01:15 +0300 |
| commit | af0e6242909c3c4297392ca3e94eff1b4db71a97 (patch) | |
| tree | 4ae786fa15f6de09bdef58c4566c737da62527ea /drivers/spi/spi-fsl-spi.c | |
| parent | a798a7086c38d91d304132c194cff9f02197f5cd (diff) | |
| download | linux-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.c | 16 |
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) { |