| Message ID | 1458048276-31884-1-git-send-email-dirk.behme@de.bosch.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 793c7f9212fdb7bea5e017427e750afa11217c29 |
| Headers | show |
On Tue, Mar 15, 2016 at 02:24:36PM +0100, Dirk Behme wrote: > From: Knut Wohlrab <knut.wohlrab@de.bosch.com> > > If the SPI chip select (CS) for a dedicated channel is done manually by > the used higher device driver, the CS may be active while writing to > ECSPIx_CONFIGREG. To prevent unwanted clock edges when selecting > the clock mode, only do the necessary changes to the i.MX SPI > configuration register and leave not selected channels untouched. > > To prevent unwanted clock edges on first use, an empty dummy > transmission shall be done by the initialization procedure of the device > driver of this channel. This will set the clock mode to the correct state. The patch does the right thing, so: Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Only the above sentence is not clear to me. By device driver you mean the SPI slave driver (flash, PMIC), right? Isn't this what bitbang->setup_transfer(spi, NULL), called from spi_bitbang_setup() already does? spi_bitbang_setup should be called while adding a new SPI slave device and the setup_transfer with an empty message should setup the config register correctly without involing the slave device driver. Sascha
Am 03/17/2016 um 08:59 AM schrieb Sascha Hauer: > On Tue, Mar 15, 2016 at 02:24:36PM +0100, Dirk Behme wrote: >> > From: Knut Wohlrab <knut.wohlrab@de.bosch.com> >> > >> > If the SPI chip select (CS) for a dedicated channel is done manually by >> > the used higher device driver, the CS may be active while writing to >> > ECSPIx_CONFIGREG. To prevent unwanted clock edges when selecting >> > the clock mode, only do the necessary changes to the i.MX SPI >> > configuration register and leave not selected channels untouched. >> > >> > To prevent unwanted clock edges on first use, an empty dummy >> > transmission shall be done by the initialization procedure of the device >> > driver of this channel. This will set the clock mode to the correct state. > The patch does the right thing, so: > > Acked-by: Sascha Hauer <s.hauer@pengutronix.de> > > Only the above sentence is not clear to me. By device driver you mean > the SPI slave driver (flash, PMIC), right? Isn't this what > bitbang->setup_transfer(spi, NULL), called from spi_bitbang_setup() already > does? spi_bitbang_setup should be called while adding a new SPI slave > device and the setup_transfer with an empty message should setup the > config register correctly without involing the slave device driver. > > Sascha > "Higher device driver" is a "historical" protocol stack to unify our data transfer via several physical interfaces, here SPI. This driver requires own control to the CS signal to start data transfer only if CS is acknowledged by the external SPI slave device via GPIO/IRQ. Therefore we can not rely on iMX6 SPI controller IP or kernel driver CS/RDY functionality. The CS signal is active before the SPI driver is involved and if the SPI driver changes the clock polarity, the unwanted clock edge is destroying the data transfer. Thanks and regards Knut -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index e7a19be..b79d70d 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -333,8 +333,9 @@ static void __maybe_unused mx51_ecspi_trigger(struct spi_imx_data *spi_imx) static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx, struct spi_imx_config *config) { - u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0; + u32 ctrl = MX51_ECSPI_CTRL_ENABLE; u32 clk = config->speed_hz, delay, reg; + u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG); /* * The hardware seems to have a race condition when changing modes. The @@ -358,13 +359,20 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx, if (config->mode & SPI_CPHA) cfg |= MX51_ECSPI_CONFIG_SCLKPHA(config->cs); + else + cfg &= ~MX51_ECSPI_CONFIG_SCLKPHA(config->cs); if (config->mode & SPI_CPOL) { cfg |= MX51_ECSPI_CONFIG_SCLKPOL(config->cs); cfg |= MX51_ECSPI_CONFIG_SCLKCTL(config->cs); + } else { + cfg &= ~MX51_ECSPI_CONFIG_SCLKPOL(config->cs); + cfg &= ~MX51_ECSPI_CONFIG_SCLKCTL(config->cs); } if (config->mode & SPI_CS_HIGH) cfg |= MX51_ECSPI_CONFIG_SSBPOL(config->cs); + else + cfg &= ~MX51_ECSPI_CONFIG_SSBPOL(config->cs); if (spi_imx->usedma) ctrl |= MX51_ECSPI_CTRL_SMC;