linux-kernel - Re: [PATCH] i2c: omap: fix i207 errata handling

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Date:	Fri, 21 Nov 2014 10:08:28 -0600
From:	Felipe Balbi <balbi@...com>
To:	Alexander Kochetkov <al.kochet@...il.com>
CC:	<linux-omap@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Wolfram Sang <wsa@...-dreams.de>,
	"Tony Lindgren" <tony@...mide.com>, Felipe Balbi <balbi@...com>,
	Aaro Koskinen <aaro.koskinen@....fi>
Subject: Re: [PATCH] i2c: omap: fix i207 errata handling

On Fri, Nov 21, 2014 at 04:16:51AM +0400, Alexander Kochetkov wrote:
> commit 6d9939f651419a63e091105663821f9c7d3fec37 (i2c: omap: split out [XR]DR
> and [XR]RDY) changed the way how errata i207 (I2C: RDR Flag May Be Incorrectly
> Set) get handled. 6d9939f6514 code doesn't correspond to workaround provided by
> errata.
> 
> According to errata ISR must filter out spurious RDR before data read not after.
> ISR must read RXSTAT to get number of bytes available to read. Because RDR
> could be set while there could no data in the receive FIFO.
> 
> Restored pre 6d9939f6514 way of handling errata.
> 
> Found by code review. Real impact haven't seen.
> Tested on Beagleboard XM C.
> 
> Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
> Fixes: 6d9939f651419a63e09110 i2c: omap: split out [XR]DR and [XR]RDY

Tested on BBB and AM437x Starter Kit

Tested-by: Felipe Balbi <balbi@...com>
Reviewed-by: Felipe Balbi <balbi@...com>

> ---
>  drivers/i2c/busses/i2c-omap.c |    8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 90dcc2e..e7cbcb0 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -958,11 +958,13 @@ omap_i2c_isr_thread(int this_irq, void *dev_id)
>  			if (dev->fifo_size)
>  				num_bytes = dev->buf_len;
>  
> -			omap_i2c_receive_data(dev, num_bytes, true);
> -
> -			if (dev->errata & I2C_OMAP_ERRATA_I207)
> +			if (dev->errata & I2C_OMAP_ERRATA_I207) {
>  				i2c_omap_errata_i207(dev, stat);
> +				num_bytes = (omap_i2c_read_reg(dev,
> +					OMAP_I2C_BUFSTAT_REG) >> 8) & 0x3F;
> +			}
>  
> +			omap_i2c_receive_data(dev, num_bytes, true);
>  			omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR);
>  			continue;
>  		}
> -- 
> 1.7.9.5
> 

-- 
balbi

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