G, Manjunath Kondaiah had written, on 04/01/2010 07:20 AM, the following:
Under certain rare conditions, I2C_STAT[13].RDR bit may be set
and the corresponding interrupt fire, even there is no data in
the receive FIFO, or the I2C data transfer is still ongoing.
These spurious RDR events must be ignored by the software.
This patch handles and ignores RDR spurious interrupts.
Reviewed-by: Kalliguddi, Hema <hemahk@xxxxxx>
Signed-off-by: Manjunatha GK <manjugk@xxxxxx>
Cc: linux-omap@xxxxxxxxxxxxxxx
Cc: linux-i2c@xxxxxxxxxxxxxxx
Cc: ben-linux@xxxxxxxxx
Cc: Kalliguddi, Hema <hemahk@xxxxxx>
---
drivers/i2c/busses/i2c-omap.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index f2019d2..acf4076 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -796,6 +796,19 @@ complete:
}
if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
u8 num_bytes = 1;
+
+ /*
+ * OMAP3 I2C Errata ID: i207
+ * Under certain rare conditions, RDR could be set again
+ * when the bus is busy, then clear and ignore the interrupt
+ */
+ if (!(stat & OMAP_I2C_STAT_RRDY) && (stat &
+ OMAP_I2C_STAT_BB)) {
+ /* clear RDR */
+ omap_i2c_ack_stat(dev, stat & OMAP_I2C_STAT_RDR);
+ dev_err(dev->dev, "I2C: RDR when bus is busy.\n");
+ return IRQ_HANDLED;
+ }
couple of comments after reading thru the errata:
a) the sequence in the errata doc is:
if (stat & OMAP_I2C_STAT_RDR) { /* This is cleaner that using an obtuse
check using !(stat & OMAP_I2C_STAT_RRDY) */
omap_i2c_ack_stat(dev, stat & OMAP_I2C_STAT_RDR); /* dummy read - i
think this needs clarification as to why */
if (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) & OMAP_I2C_STAT_BB) /*
reason for the i2c_read_reg is because errata mentions a dummy stat read
which might mean something for BB -> I am not sure may need to be
checked with H/w team. */
continue; /* recheck - faster response compared to return and re
generate interrupt */
}
b) does this apply to OMAP2 and OMAP4?
(unrelated sidenote: my usual crib: we probably need an errata
management system soon considering the erratas that are getting
workedaround in code.. :( )..
if (dev->fifo_size) {
if (stat & OMAP_I2C_STAT_RRDY)
num_bytes = dev->fifo_size;
--
Regards,
Nishanth Menon
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