| Message ID | 1438092193-31799-1-git-send-email-kernel@martin.sperl.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | ca861dd0c5e36c4a2cf454049a45a961c855290a |
| Headers | show |
Any feedback on this patch? Can this get merged? Noralf (via private communication) has confirmed that with this patch his fbtft device (which uses spi-cpol and spi-cpha) works. Thanks, Martin On 28.07.2015 16:03, kernel@martin.sperl.org wrote: > From: Martin Sperl <kernel@martin.sperl.org> > > When using reverse polarity for clock (spi-cpol) on a device > the clock line gets altered after chip-select has been asserted > resulting in an additional clock beat, which confuses hardware. > > This did not show when using native-CS, as the same register > is used to control cs as well as polarity, so the changes came > into effect at the same time. Unfortunately this is not true > with gpio-cs. > > To avoid this situation this patch moves the setup of polarity > (spi-cpol and spi-cpha) outside of the chip-select into > prepare_message, which is run prior to asserting chip-select. > > Also fixes resetting 3-wire mode after use of rx-mode, so that > a 3-Wire sequence TX, RX, TX works as well (right now it runs > TX, RX, RX instead) > > Reported-by: Noralf Tronnes <noralf@tronnes.org> > Signed-off-by: Martin Sperl <kernel@martin.sperl.org> > --- > drivers/spi/spi-bcm2835.c | 28 +++++++++++++++++++++++----- > 1 file changed, 23 insertions(+), 5 deletions(-) > > See also the images for the effect that this patch has on the signals: > https://github.com/raspberrypi/linux/pull/1077#issuecomment-125484500 > > diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c > index 59705ab..c9357bb 100644 > --- a/drivers/spi/spi-bcm2835.c > +++ b/drivers/spi/spi-bcm2835.c > @@ -553,13 +553,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, > spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536); > bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); > > - /* handle all the modes */ > + /* handle all the 3-wire mode */ > if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf)) > cs |= BCM2835_SPI_CS_REN; > - if (spi->mode & SPI_CPOL) > - cs |= BCM2835_SPI_CS_CPOL; > - if (spi->mode & SPI_CPHA) > - cs |= BCM2835_SPI_CS_CPHA; > + else > + cs &= ~BCM2835_SPI_CS_REN; > > /* for gpio_cs set dummy CS so that no HW-CS get changed > * we can not run this in bcm2835_spi_set_cs, as it does > @@ -592,6 +590,25 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, > return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs); > } > > +static int bcm2835_spi_prepare_message(struct spi_master *master, > + struct spi_message *msg) > +{ > + struct spi_device *spi = msg->spi; > + struct bcm2835_spi *bs = spi_master_get_devdata(master); > + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); > + > + cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA); > + > + if (spi->mode & SPI_CPOL) > + cs |= BCM2835_SPI_CS_CPOL; > + if (spi->mode & SPI_CPHA) > + cs |= BCM2835_SPI_CS_CPHA; > + > + bcm2835_wr(bs, BCM2835_SPI_CS, cs); > + > + return 0; > +} > + > static void bcm2835_spi_handle_err(struct spi_master *master, > struct spi_message *msg) > { > @@ -739,6 +756,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) > master->set_cs = bcm2835_spi_set_cs; > master->transfer_one = bcm2835_spi_transfer_one; > master->handle_err = bcm2835_spi_handle_err; > + master->prepare_message = bcm2835_spi_prepare_message; > master->dev.of_node = pdev->dev.of_node; > > bs = spi_master_get_devdata(master); > -- 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
On Tue, Aug 04, 2015 at 12:12:59PM +0200, Martin Sperl wrote: > Any feedback on this patch? Can this get merged? > > Noralf (via private communication) has confirmed that with > this patch his fbtft device (which uses spi-cpol and spi-cpha) > works. > On 28.07.2015 16:03, kernel@martin.sperl.org wrote: Please don't top post or send content free pings, and please allow a reasonable time for review - you only posted this last week.
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 59705ab..c9357bb 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -553,13 +553,11 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536); bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); - /* handle all the modes */ + /* handle all the 3-wire mode */ if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf)) cs |= BCM2835_SPI_CS_REN; - if (spi->mode & SPI_CPOL) - cs |= BCM2835_SPI_CS_CPOL; - if (spi->mode & SPI_CPHA) - cs |= BCM2835_SPI_CS_CPHA; + else + cs &= ~BCM2835_SPI_CS_REN; /* for gpio_cs set dummy CS so that no HW-CS get changed * we can not run this in bcm2835_spi_set_cs, as it does @@ -592,6 +590,25 @@ static int bcm2835_spi_transfer_one(struct spi_master *master, return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs); } +static int bcm2835_spi_prepare_message(struct spi_master *master, + struct spi_message *msg) +{ + struct spi_device *spi = msg->spi; + struct bcm2835_spi *bs = spi_master_get_devdata(master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA); + + if (spi->mode & SPI_CPOL) + cs |= BCM2835_SPI_CS_CPOL; + if (spi->mode & SPI_CPHA) + cs |= BCM2835_SPI_CS_CPHA; + + bcm2835_wr(bs, BCM2835_SPI_CS, cs); + + return 0; +} + static void bcm2835_spi_handle_err(struct spi_master *master, struct spi_message *msg) { @@ -739,6 +756,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) master->set_cs = bcm2835_spi_set_cs; master->transfer_one = bcm2835_spi_transfer_one; master->handle_err = bcm2835_spi_handle_err; + master->prepare_message = bcm2835_spi_prepare_message; master->dev.of_node = pdev->dev.of_node; bs = spi_master_get_devdata(master);