Re: [PATCH v3] OMAP2/3: I2C: Errata ID i207: Clear wrong RDR interrupt

[Aaro Koskinen <aaro.koskinen-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>]

Hi,

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.
> 
> Signed-off-by: Manjunatha GK <manjugk-l0cyMroinI0@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>
> Cc: Nishanth Menon <nm-l0cyMroinI0@public.gmane.org>
> 
> ---
>  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 ae6f5c1..d1648da 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -733,6 +733,34 @@ 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, stat & OMAP_I2C_STAT_RDR);

You know the bit is set, so just: 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, stat
> +							& OMAP_I2C_STAT_RDR);

Same here.

> +						dev_err(dev->dev,
> +						"I2C : RDR when the bus is busy.\n");

Remove the "I2C : " from the log, it's redundant.

> +						continue;
> +					}
> +
> +				}
> +			}
>  			if (dev->fifo_size) {
>  				if (stat & OMAP_I2C_STAT_RRDY)
>  					num_bytes = dev->fifo_size;