| Message ID | 1427812501-7194-1-git-send-email-m.grzeschik@pengutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Mar 31, 2015 at 04:35:01PM +0200, Michael Grzeschik wrote: > 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. Applied, thanks.
On Tue, Mar 31, 2015 at 4:35 PM, Michael Grzeschik <m.grzeschik@pengutronix.de> wrote: > 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> > --- > v2: added missing braces > > drivers/spi/spi-bitbang-txrx.h | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h > index c616e41..06b34e5 100644 > --- a/drivers/spi/spi-bitbang-txrx.h > +++ b/drivers/spi/spi-bitbang-txrx.h > @@ -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 */ > > + bool oldbit = !(word & 1); Is it intentional you check the first bit (word & 1) here? Everywhere else you use (word & 31). > /* clock starts at inactive polarity */ > for (word <<= (32 - bits); likely(bits); bits--) { > > /* setup MSB (to slave) on trailing edge */ > - if ((flags & SPI_MASTER_NO_TX) == 0) > - setmosi(spi, word & (1 << 31)); > + if ((flags & SPI_MASTER_NO_TX) == 0) { > + if ((word & (1 << 31)) != oldbit) { You are comparing a bool to an int, and ((word & (1 << 31)) will always be != true (== 1). Your condition needs to be !!(word & (1 << 31)) != oldbit . > + setmosi(spi, word & (1 << 31)); > + oldbit = word & (1 << 31); > + } > + } > spidelay(nsecs); /* T(setup) */ > > 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 */ > > + bool oldbit = !(word & (1 << 31)); > /* clock starts at inactive polarity */ > for (word <<= (32 - bits); likely(bits); bits--) { > > /* setup MSB (to slave) on leading edge */ > setsck(spi, !cpol); > - if ((flags & SPI_MASTER_NO_TX) == 0) > - setmosi(spi, word & (1 << 31)); > + if ((flags & SPI_MASTER_NO_TX) == 0) { > + if ((word & (1 << 31)) != oldbit) { Same issue here. > + setmosi(spi, word & (1 << 31)); > + oldbit = word & (1 << 31); > + } > + } > spidelay(nsecs); /* T(setup) */ > > setsck(spi, cpol); > -- Regards Jonas
On Tue, Mar 31, 2015 at 08:59:28PM +0200, Jonas Gorski wrote: > On Tue, Mar 31, 2015 at 4:35 PM, Michael Grzeschik > <m.grzeschik@pengutronix.de> wrote: > > 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> > > --- > > v2: added missing braces > > > > drivers/spi/spi-bitbang-txrx.h | 18 ++++++++++++++---- > > 1 file changed, 14 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h > > index c616e41..06b34e5 100644 > > --- a/drivers/spi/spi-bitbang-txrx.h > > +++ b/drivers/spi/spi-bitbang-txrx.h > > @@ -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 */ > > > > + bool oldbit = !(word & 1); > > Is it intentional you check the first bit (word & 1) here? Everywhere > else you use (word & 31). Doh! I was reworking this from an _le_ variant of the same code. This hunk unfortunately is an leftover... :/ Mark, should I send a corrected version or do you squash the 31 into the applied patch? Thanks for the hint, Michael
On Tue, Mar 31, 2015 at 10:13:00PM +0200, Michael Grzeschik wrote: > Mark, should I send a corrected version or do you squash the 31 into the > applied patch? If you could send me a patch (either incremental or squashed is fine) that'd be good - I'd prefer to have something from you as I'd need to set up a test system for bitbang.
diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h index c616e41..06b34e5 100644 --- a/drivers/spi/spi-bitbang-txrx.h +++ b/drivers/spi/spi-bitbang-txrx.h @@ -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 */ + bool oldbit = !(word & 1); /* clock starts at inactive polarity */ for (word <<= (32 - bits); likely(bits); bits--) { /* setup MSB (to slave) on trailing edge */ - if ((flags & SPI_MASTER_NO_TX) == 0) - setmosi(spi, word & (1 << 31)); + if ((flags & SPI_MASTER_NO_TX) == 0) { + if ((word & (1 << 31)) != oldbit) { + setmosi(spi, word & (1 << 31)); + oldbit = word & (1 << 31); + } + } spidelay(nsecs); /* T(setup) */ 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 */ + bool oldbit = !(word & (1 << 31)); /* clock starts at inactive polarity */ for (word <<= (32 - bits); likely(bits); bits--) { /* setup MSB (to slave) on leading edge */ setsck(spi, !cpol); - if ((flags & SPI_MASTER_NO_TX) == 0) - setmosi(spi, word & (1 << 31)); + if ((flags & SPI_MASTER_NO_TX) == 0) { + if ((word & (1 << 31)) != oldbit) { + setmosi(spi, word & (1 << 31)); + oldbit = word & (1 << 31); + } + } spidelay(nsecs); /* T(setup) */ setsck(spi, cpol);
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> --- v2: added missing braces drivers/spi/spi-bitbang-txrx.h | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)