From: Jonas Gorski <jogo-p3rKhJxN3npAfugRpC6u6w@public.gmane.org> To: Michael Grzeschik <m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Cc: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org Subject: Re: [PATCH v2] spi: bitbang: only toggle bitchanges Date: Tue, 31 Mar 2015 20:59:28 +0200 [thread overview] Message-ID: <CAOiHx=k_NhSgzUDNPGXLUWN9r9bJ1rbsv3vLg_gFKpuinEqKmA@mail.gmail.com> (raw) In-Reply-To: <1427812501-7194-1-git-send-email-m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> On Tue, Mar 31, 2015 at 4:35 PM, Michael Grzeschik <m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 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-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
WARNING: multiple messages have this Message-ID (diff)
From: jogo@openwrt.org (Jonas Gorski) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2] spi: bitbang: only toggle bitchanges Date: Tue, 31 Mar 2015 20:59:28 +0200 [thread overview] Message-ID: <CAOiHx=k_NhSgzUDNPGXLUWN9r9bJ1rbsv3vLg_gFKpuinEqKmA@mail.gmail.com> (raw) In-Reply-To: <1427812501-7194-1-git-send-email-m.grzeschik@pengutronix.de> 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
next prev parent reply other threads:[~2015-03-31 18:59 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-03-31 13:54 [PATCH] spi: bitbang: only toggle bitchanges Michael Grzeschik 2015-03-31 13:54 ` Michael Grzeschik [not found] ` <1427810089-14866-1-git-send-email-m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2015-03-31 14:13 ` Mark Brown 2015-03-31 14:13 ` Mark Brown [not found] ` <20150331141321.GR2869-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> 2015-03-31 14:35 ` [PATCH v2] " Michael Grzeschik 2015-03-31 14:35 ` Michael Grzeschik [not found] ` <1427812501-7194-1-git-send-email-m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2015-03-31 16:21 ` Mark Brown 2015-03-31 16:21 ` Mark Brown 2015-03-31 18:59 ` Jonas Gorski [this message] 2015-03-31 18:59 ` Jonas Gorski [not found] ` <CAOiHx=k_NhSgzUDNPGXLUWN9r9bJ1rbsv3vLg_gFKpuinEqKmA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2015-03-31 20:13 ` Michael Grzeschik 2015-03-31 20:13 ` Michael Grzeschik [not found] ` <20150331201300.GB12253-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2015-03-31 20:23 ` Mark Brown 2015-03-31 20:23 ` Mark Brown [not found] ` <20150331202306.GX2869-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> 2015-04-13 10:59 ` [PATCH v3] " Michael Grzeschik 2015-04-13 10:59 ` Michael Grzeschik [not found] ` <1428922770-16955-1-git-send-email-m.grzeschik-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2015-04-18 12:09 ` Mark Brown 2015-04-18 12:09 ` Mark Brown [not found] ` <20150418120926.GL26185-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> 2015-04-18 13:18 ` Marc Kleine-Budde 2015-04-18 13:18 ` Marc Kleine-Budde [not found] ` <db1d2b9a-730b-40a5-a4f6-091fd3fad0e7-2ueSQiBKiTY7tOexoI0I+QC/G2K4zDHf@public.gmane.org> 2015-04-18 17:16 ` Mark Brown 2015-04-18 17:16 ` Mark Brown
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