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spi: bitbang: only toggle bitchanges

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The current implementation of bitbang_txrx_be_cpha0 and
bitbang_txrx_be_cpha1 always call setmosi. That runs into several
unnecessary calls into the gpiolib when the level of the GPIO actually
has not to be changed.

This patch changes the routines to remember the last GPIO level
and only calls setmosi if an change has to be made. This
way it improves the transfer throughput.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Michael Grzeschik 2015-03-31 16:35:01 +02:00 committed by Mark Brown
parent c517d838eb
commit 232a5adc51
1 changed files with 14 additions and 4 deletions
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18
drivers/spi/spi-bitbang-txrx.h
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@ -49,12 +49,17 @@ bitbang_txrx_be_cpha0(struct spi_device *spi,
{ {
/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
bool oldbit = !(word & 1);
/* clock starts at inactive polarity */ /* clock starts at inactive polarity */
for (word <<= (32 - bits); likely(bits); bits--) { for (word <<= (32 - bits); likely(bits); bits--) {
/* setup MSB (to slave) on trailing edge */ /* setup MSB (to slave) on trailing edge */
if ((flags & SPI_MASTER_NO_TX) == 0) if ((flags & SPI_MASTER_NO_TX) == 0) {
setmosi(spi, word & (1 << 31)); if ((word & (1 << 31)) != oldbit) {
setmosi(spi, word & (1 << 31));
oldbit = word & (1 << 31);
}
}
spidelay(nsecs); /* T(setup) */ spidelay(nsecs); /* T(setup) */
setsck(spi, !cpol); setsck(spi, !cpol);
@ -76,13 +81,18 @@ bitbang_txrx_be_cpha1(struct spi_device *spi,
{ {
/* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */ /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */
bool oldbit = !(word & (1 << 31));
/* clock starts at inactive polarity */ /* clock starts at inactive polarity */
for (word <<= (32 - bits); likely(bits); bits--) { for (word <<= (32 - bits); likely(bits); bits--) {
/* setup MSB (to slave) on leading edge */ /* setup MSB (to slave) on leading edge */
setsck(spi, !cpol); setsck(spi, !cpol);
if ((flags & SPI_MASTER_NO_TX) == 0) if ((flags & SPI_MASTER_NO_TX) == 0) {
setmosi(spi, word & (1 << 31)); if ((word & (1 << 31)) != oldbit) {
setmosi(spi, word & (1 << 31));
oldbit = word & (1 << 31);
}
}
spidelay(nsecs); /* T(setup) */ spidelay(nsecs); /* T(setup) */
setsck(spi, cpol); setsck(spi, cpol);