Re: [PATCH] OMAP3: I2C: Errata i207: Clear wrong RDR interrupt

Ben Dooks
2010-04-05T22:45:24Z

On Thu, Apr 01, 2010 at 08:53:04AM -0500, Nishanth Menon wrote:
> 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-l0cyMroinI0@public.gmane.org>
> >Signed-off-by: Manjunatha GK <manjugk-l0cyMroinI0@public.gmane.org>
> >Cc: linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> >Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> >Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org
> >Cc: Kalliguddi, Hema <hemahk-l0cyMroinI0@public.gmane.org>
> >---
> > 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?

Ok, should this be held for further discussion?

--
Ben (ben-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, http://www.fluff.org/)

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