On Thu, Oct 14, 2010 at 5:14 AM, Jason Wang <jason77.wang@xxxxxxxxx> wrote: > Grazvydas Ignotas wrote: >> Working here on pandora too, applied on top of linux-next (did not >> test suspend though). >> >> Not caused by this patch, but the old problem where lower measurement >> bits get lost is back - when I draw diagonal line it looks like >> stairs. I think it's caused by OMAP SPI driver, CCing linux-omap. >> >> > > Yes, it is OMAP spi driver issues, I have met the same problem before, > please refer to: > http://www.spinics.net/lists/arm-kernel/msg91538.html > > you can apply this patch and test again. It solves my issue, thanks Tested-by: Grazvydas Ignotas <notasas@xxxxxxxxx> BTW I have done similar patch almost 2 years ago for exactly the same problem: http://marc.info/?l=linux-omap&m=122565580616920&w=2 but then problem went away after random kernel update (from what I remember), and my patch was no longer needed. > From 393f445ab899abaf5d60a55a54f242c430507047 Mon Sep 17 00:00:00 2001 > From: Jason Wang <jason77.wang@xxxxxxxxx> > Date: Thu, 14 Oct 2010 10:08:07 +0800 > Subject: [PATCH] spi/omap2_mcspi: disable channel after TX_ONLY transfer in > PIO mode > > In TX_ONLY transfer, the SPI controller can also receive data > simultaneously and saves them in rx register. After the TX_ONLY > transfer, the rx register will hold random data received during > last tx transaction. > > If the next transfer is RX_ONLY, this random data has > the possibility to affect this transfer like this: > > If the spi controller is changed from TX_ONLY to RX_ONLY mode, > The random data makes the rx register full imediately and > triggers a dummy write (in SPI RX_ONLY transfer, we need a dummy > write to trigger the first transaction). > > So the first data received in RX_ONLY transfer will be that > random data instead of something meaningfug. > > We can avoid this by a Disable/reenable toggle of the spi channel > after the TX_ONLY transfer, since it purges the rx register. > > Signed-off-by: Jason Wang <jason77.wang@xxxxxxxxx> > --- > 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-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
