From: Trent Piepho <tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> To: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Cc: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>, Fabio Estevam <fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, Trent Piepho <tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> Subject: [PATCH V2 11/12] spi/mxs: Don't set clock for each xfer Date: Tue, 2 Apr 2013 05:19:54 -0700 [thread overview] Message-ID: <1364905195-24286-11-git-send-email-tpiepho@gmail.com> (raw) In-Reply-To: <1364905195-24286-1-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> mxs_spi_setup_transfer() would set the SSP SCK rate every time it was called, which is before each transfer. It is uncommon for the SCK rate to change between transfers and this causes unnecessary reprogramming of the clock registers. Changed to only set the rate when it has changed. This significantly speeds up short SPI messages, especially messages made up of many transfers. On an iMX287, using spidev with messages that consist of 511 transfers of 4 bytes each at an SCK of 48 MHz, the effective transfer rate more than doubles from about 290 KB/sec to 600 KB/sec. Signed-off-by: Trent Piepho <tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Cc: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org> Cc: Fabio Estevam <fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org> Cc: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> --- drivers/spi/spi-mxs.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c index a7d5f85..12794ea 100644 --- a/drivers/spi/spi-mxs.c +++ b/drivers/spi/spi-mxs.c @@ -68,6 +68,7 @@ struct mxs_spi { struct mxs_ssp ssp; struct completion c; + unsigned int sck; /* Rate requested (vs actual) */ }; static int mxs_spi_setup_transfer(struct spi_device *dev, @@ -88,7 +89,19 @@ static int mxs_spi_setup_transfer(struct spi_device *dev, return -EINVAL; } - mxs_ssp_set_clk_rate(ssp, hz); + if (hz != spi->sck) { + mxs_ssp_set_clk_rate(ssp, hz); + /* + * Save requested value, not actual value from ssp->clk_rate. + * Otherwise we would set the rate again each trasfer when + * actual is not quite the same as requested. + */ + spi->sck = hz; + /* + * Perhaps we should return an error if the actual clock is + * nowhere close to what was requested? + */ + } writel(BM_SSP_CTRL0_LOCK_CS, ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET); -- 1.7.10.4 ------------------------------------------------------------------------------ Own the Future-Intel(R) Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://altfarm.mediaplex.com/ad/ck/12124-176961-30367-2
WARNING: multiple messages have this Message-ID (diff)
From: tpiepho@gmail.com (Trent Piepho) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH V2 11/12] spi/mxs: Don't set clock for each xfer Date: Tue, 2 Apr 2013 05:19:54 -0700 [thread overview] Message-ID: <1364905195-24286-11-git-send-email-tpiepho@gmail.com> (raw) In-Reply-To: <1364905195-24286-1-git-send-email-tpiepho@gmail.com> mxs_spi_setup_transfer() would set the SSP SCK rate every time it was called, which is before each transfer. It is uncommon for the SCK rate to change between transfers and this causes unnecessary reprogramming of the clock registers. Changed to only set the rate when it has changed. This significantly speeds up short SPI messages, especially messages made up of many transfers. On an iMX287, using spidev with messages that consist of 511 transfers of 4 bytes each at an SCK of 48 MHz, the effective transfer rate more than doubles from about 290 KB/sec to 600 KB/sec. Signed-off-by: Trent Piepho <tpiepho@gmail.com> Cc: Marek Vasut <marex@denx.de> Cc: Fabio Estevam <fabio.estevam@freescale.com> Cc: Shawn Guo <shawn.guo@linaro.org> --- drivers/spi/spi-mxs.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c index a7d5f85..12794ea 100644 --- a/drivers/spi/spi-mxs.c +++ b/drivers/spi/spi-mxs.c @@ -68,6 +68,7 @@ struct mxs_spi { struct mxs_ssp ssp; struct completion c; + unsigned int sck; /* Rate requested (vs actual) */ }; static int mxs_spi_setup_transfer(struct spi_device *dev, @@ -88,7 +89,19 @@ static int mxs_spi_setup_transfer(struct spi_device *dev, return -EINVAL; } - mxs_ssp_set_clk_rate(ssp, hz); + if (hz != spi->sck) { + mxs_ssp_set_clk_rate(ssp, hz); + /* + * Save requested value, not actual value from ssp->clk_rate. + * Otherwise we would set the rate again each trasfer when + * actual is not quite the same as requested. + */ + spi->sck = hz; + /* + * Perhaps we should return an error if the actual clock is + * nowhere close to what was requested? + */ + } writel(BM_SSP_CTRL0_LOCK_CS, ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET); -- 1.7.10.4
next prev parent reply other threads:[~2013-04-02 12:19 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-04-02 12:19 [PATCH V2 01/12] spi/mxs: Always set LOCK_CS Trent Piepho 2013-04-02 12:19 ` Trent Piepho [not found] ` <1364905195-24286-1-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 12:19 ` [PATCH V2 02/12] spi/mxs: Remove mxs_spi_enable and mxs_spi_disable Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 03/12] spi/mxs: Change flag arguments in txrx functions to bit flags Trent Piepho 2013-04-02 12:19 ` Trent Piepho [not found] ` <1364905195-24286-3-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 23:24 ` Marek Vasut 2013-04-02 23:24 ` Marek Vasut 2013-04-02 12:19 ` [PATCH V2 04/12] spi/mxs: Fix extra CS pulses and read mode in multi-transfer messages Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 05/12] spi/mxs: Fix chip select control bits in DMA mode Trent Piepho 2013-04-02 12:19 ` Trent Piepho [not found] ` <1364905195-24286-5-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 23:29 ` Marek Vasut 2013-04-02 23:29 ` Marek Vasut 2013-04-02 12:19 ` [PATCH V2 06/12] spi/mxs: Remove full duplex check, spi core already does it Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 07/12] spi/mxs: Remove bogus setting of ssp clk rate field Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 08/12] spi/mxs: Fix race in setup method Trent Piepho 2013-04-02 12:19 ` Trent Piepho [not found] ` <1364905195-24286-8-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 23:31 ` Marek Vasut 2013-04-02 23:31 ` Marek Vasut [not found] ` <201304030131.37782.marex-ynQEQJNshbs@public.gmane.org> 2013-04-03 2:12 ` Trent Piepho 2013-04-03 2:12 ` Trent Piepho 2013-04-03 2:27 ` Marek Vasut 2013-04-03 2:27 ` Marek Vasut [not found] ` <201304030427.41297.marex-ynQEQJNshbs@public.gmane.org> 2013-04-03 6:08 ` Trent Piepho 2013-04-03 6:08 ` Trent Piepho [not found] ` <CA+7tXih2r6YFE80y7z7Nj7c0Ytvh+v56-SrbS+VQ7kCW3KBRXA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2013-04-03 6:50 ` Marek Vasut 2013-04-03 6:50 ` Marek Vasut [not found] ` <201304030850.31752.marex-ynQEQJNshbs@public.gmane.org> 2013-04-03 9:32 ` Trent Piepho 2013-04-03 9:32 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 09/12] spi/mxs: Remove check of spi mode bits Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 12:19 ` [PATCH V2 10/12] spi/mxs: Clean up setup_transfer function Trent Piepho 2013-04-02 12:19 ` Trent Piepho [not found] ` <1364905195-24286-10-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 23:35 ` Marek Vasut 2013-04-02 23:35 ` Marek Vasut 2013-04-02 12:19 ` Trent Piepho [this message] 2013-04-02 12:19 ` [PATCH V2 11/12] spi/mxs: Don't set clock for each xfer Trent Piepho [not found] ` <1364905195-24286-11-git-send-email-tpiepho-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2013-04-02 23:38 ` Marek Vasut 2013-04-02 23:38 ` Marek Vasut 2013-04-02 12:19 ` [PATCH V2 12/12] spi/mxs: Use u32 instead of uint32_t Trent Piepho 2013-04-02 12:19 ` Trent Piepho 2013-04-02 23:18 ` [PATCH V2 01/12] spi/mxs: Always set LOCK_CS Marek Vasut 2013-04-02 23:18 ` Marek Vasut [not found] ` <201304030118.42976.marex-ynQEQJNshbs@public.gmane.org> 2013-07-10 13:49 ` Fabio Estevam 2013-07-10 13:49 ` Fabio Estevam 2013-07-10 15:29 ` Lothar Waßmann 2013-07-10 15:29 ` Lothar Waßmann [not found] ` <20957.32214.721252.361301-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org> 2013-07-18 1:08 ` Trent Piepho 2013-04-03 1:41 ` Shawn Guo 2013-04-03 1:41 ` Shawn Guo 2013-04-14 18:01 ` Marek Vasut 2013-04-14 18:01 ` Marek Vasut
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