On Mon, Apr 19, 2010 at 12:44:22PM +0530, Manjunatha GK wrote:
> 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.
>
> The below sequence is required in interrupt handler for
> handling this errata:
> 1. If RDR is set to 1, clear RDR
> 2. Read I2C status register and check for BusBusy bit. If BusBusy
> bit is set, skip remaining steps.
> 3. If BusBusy bit is not set, perform read operation on I2C status
> register.
> 4. If RDR is set, clear the same. Check RDR again and clear if it sets
> RDR bit again.
> 5. Perform I2C Data Read operation N number of times(where N is value
> read from the register BUFSTAT-RXSTAT bit fields).
>
> Note : This errata is applicable for OMAP2 and OMAP3 platforms only.
> It is not applicable for OMAP4.
If people can give me a yes/no before the end of play tomorrow (ie,
2300GMT) then I will get this applied to for-linus/i2c and send it
for -rc.
> Signed-off-by: Manjunatha GK <manjugk@xxxxxx>
> Cc: linux-i2c@xxxxxxxxxxxxxxx
> Cc: ben-linux@xxxxxxxxx
> Cc: Kalliguddi, Hema <hemahk@xxxxxx>
> Cc: Nishanth Menon <nm@xxxxxx>
> Cc: Aaro Koskinen <Aaro.Koskinen@xxxxxxxxx>
>
> ---
> drivers/i2c/busses/i2c-omap.c | 28 ++++++++++++++++++++++++++++
> 1 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index f2019d2..8309eac 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -796,6 +796,34 @@ complete:
> }
> if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
> u8 num_bytes = 1;
> +
> + /*
> + * I2C Errata(Errata Nos. OMAP2: 1.67, OMAP3: 1.8)
> + * Not applicable for OMAP4.
> + * Under certain rare conditions, RDR could be set again
> + * when the bus is busy, then ignore the interrupt and
> + * clear the interrupt.
> + */
> + if ((stat & OMAP_I2C_STAT_RDR) && !cpu_is_omap44xx()) {
> + /* Step 1: If RDR is set, clear it */
> + omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR);
> +
> + /* Step 2: */
> + if(!(omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG)
> + & OMAP_I2C_STAT_BB)) {
> + /* Step 3: */
> + if(omap_i2c_read_reg(dev,
> + OMAP_I2C_STAT_REG)
> + & OMAP_I2C_STAT_RDR) {
> + omap_i2c_ack_stat(dev,
> + OMAP_I2C_STAT_RDR);
> + dev_err(dev->dev,
> + "RDR when the bus is busy.\n");
> + continue;
> + }
> +
> + }
> + }
> if (dev->fifo_size) {
> if (stat & OMAP_I2C_STAT_RRDY)
> num_bytes = dev->fifo_size;
> --
> 1.6.0.4
>
> --
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--
Ben (ben@xxxxxxxxx, http://www.fluff.org/)
'a smiley only costs 4 bytes'
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