Grazvydas Ignotas wrote:
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.
Really similar problem and similar solution, :-)
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
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