linux-kernel - Re: [PATCH v2 3/8] i2c: bcm2835: Use ratelimited logging on transfer errors

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Date:   Tue, 27 Sep 2016 15:01:54 +0200
From:   Martin Sperl <kernel@...tin.sperl.org>
To:     Noralf Trønnes <noralf@...nnes.org>
Cc:     wsa@...-dreams.de, swarren@...dotorg.org, eric@...olt.net,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v2 3/8] i2c: bcm2835: Use ratelimited logging on transfer errors


> On 27 Sep 2016, at 13:57, Noralf Trønnes <noralf@...nnes.org> wrote:
> 
> Writing to an AT24C32 generates on average 2x i2c transfer errors per
> 32-byte page write. Which amounts to a lot for a 4k write. This is due
> to the fact that the chip doesn't respond during it's internal write
> cycle when the at24 driver tries and retries the next write.
> Reduce this flooding of the log by using dev_err_ratelimited().
> 
> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> Reviewed-by: Eric Anholt <eric@...olt.net>
> ---
> drivers/i2c/busses/i2c-bcm2835.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
> index df036ed..370a322 100644
> --- a/drivers/i2c/busses/i2c-bcm2835.c
> +++ b/drivers/i2c/busses/i2c-bcm2835.c
> @@ -207,7 +207,8 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
>        (msg->flags & I2C_M_IGNORE_NAK))
>        return 0;
> 
> -    dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
> +    dev_err_ratelimited(i2c_dev->dev, "i2c transfer failed: %x\n",
> +                i2c_dev->msg_err);
Do we really need this error message at all?

Maybe just remove it instead, because error messages during 
"normal"/successfull operations of at24 seems  strange.

Or make it a debug message instead.

Martin