Re: [PATCH v6] OMAP2/3: I2C: Errata ID i207: Clear wrong RDR interrupt

[Nishanth Menon <nm-l0cyMroinI0@public.gmane.org>]

very minor comments below:
On 04/28/2010 12:47 AM, G, Manjunath Kondaiah 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>
> Cc: Aaro Koskinen<Aaro.Koskinen-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>
> Cc: Tony Lindgren<tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
> ---
>   drivers/i2c/busses/i2c-omap.c |   40 ++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 40 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index ef73483..cdcdfeb 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -166,6 +166,8 @@ enum {
>   #define SYSC_IDLEMODE_SMART		0x2
>   #define SYSC_CLOCKACTIVITY_FCLK		0x2
>
> +/* Errata definitions */
> +#define I2C_OMAP_ERRATA_I207		(1<<  0)
                                         ^^^^
                               tiny nit: s/1<</1 << (need a space)
>
>   struct omap_i2c_dev {
>   	struct device		*dev;
> @@ -199,6 +201,7 @@ struct omap_i2c_dev {
>   	u16			bufstate;
>   	u16			syscstate;
>   	u16			westate;
> +	u16			errata;
overall I'd prefer the term quirk over errata - quirk is more of a 
standard linux term used accross network, usb and other drivers, will 
allow the code to be a little more familiar with the upstream 
maintainers/reviewers.. but i leave it to tony and others to comment 
more.. maybe it is just me being an ass again ;)

>   };
>
>   const static u8 reg_map[] = {
> @@ -498,6 +501,11 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
>   	/* Take the I2C module out of reset: */
>   	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
>
> +	dev->errata = 0;
> +
> +	if (cpu_is_omap2430() || cpu_is_omap34xx())
                    ^^^^^^^^ wont cpu_is_omap24xx() cover omap2420 as 
well? I think it might be better using that.. apologies on missing it in 
the last look.

> +		dev->errata |= I2C_OMAP_ERRATA_I207;
> +
>   	/* Enable interrupts */
>   	dev->iestate = (OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY |
>   			OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK |
> @@ -695,6 +703,34 @@ omap_i2c_ack_stat(struct omap_i2c_dev *dev, u16 stat)
>   	omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, stat);
>   }
>
> +static inline void i2c_omap_errata_i207(struct omap_i2c_dev *dev, u16 stat)
> +{
> +	/*
> +	 * 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) {
> +		/* 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_dbg(dev->dev, "RDR when bus is busy.\n");
> +			}
> +
> +		}
> +	}
> +}
> +
>   /* rev1 devices are apparently only on some 15xx */
>   #ifdef CONFIG_ARCH_OMAP15XX
>
> @@ -826,6 +862,10 @@ complete:
>   		}
>   		if (stat&  (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
>   			u8 num_bytes = 1;
> +
> +			if (dev->errata&  I2C_OMAP_ERRATA_I207)
> +				i2c_omap_errata_i207(dev, stat);
> +
>   			if (dev->fifo_size) {
>   				if (stat&  OMAP_I2C_STAT_RRDY)
>   					num_bytes = dev->fifo_size;

Thanks, sparse and checkpatch are happy now :)
Regards,
Nishanth Menon