On Tue, Oct 19, 2010 at 06:03:27PM +0800, Jason Wang wrote: > In the TX_ONLY transfer, the SPI controller also receives data > simultaneously and saves them in the rx register. After the TX_ONLY > transfer, the rx register will hold the random data received during > the last tx transaction. > > If the direct following transfer is RX_ONLY, this random data has the > possibility to affect this transfer like this: > When the SPI controller is changed from TX_ONLY to RX_ONLY, > the random data makes the rx register full immediately and > triggers a dummy write automatically(in SPI RX_ONLY transfers, > we need a dummy write to trigger the first transaction). > > So the first data received in the RX_ONLY transfer will be that > random data instead of something meaningful. > > We can avoid this by inserting a Disable/Re-enable toggle of the > channel after the TX_ONLY transfer, since it purges the rx register. > > Signed-off-by: Jason Wang <jason77.wang@xxxxxxxxx> > Tested-by: Grazvydas Ignotas <notasas@xxxxxxxxx> > Acked-by: Tony Lindgren <tony@xxxxxxxxxxx> Applied, thanks. g. > --- > Hi Grant, > > The touchpanel driver can't work correctly on the omap3evm platform, > This is due to a omap2_mcspi driver issue, now fix it. > > drivers/spi/omap2_mcspi.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c > index b3a94ca..43fab41 100644 > --- a/drivers/spi/omap2_mcspi.c > +++ b/drivers/spi/omap2_mcspi.c > @@ -644,6 +644,12 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer) > } else if (mcspi_wait_for_reg_bit(chstat_reg, > OMAP2_MCSPI_CHSTAT_EOT) < 0) > dev_err(&spi->dev, "EOT timed out\n"); > + > + /* disable chan to purge rx datas received in TX_ONLY transfer, > + * otherwise these rx datas will affect the direct following > + * RX_ONLY transfer. > + */ > + omap2_mcspi_set_enable(spi, 0); > } > out: > omap2_mcspi_set_enable(spi, 1); > -- > 1.5.6.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
