linux-kernel - Re: [PATCH v3 1/7] mfd: cros_ec: spi: calculate delay between transfers correctly

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Message-ID: <20140520084358.GB24991@lee--X1>
Date:	Tue, 20 May 2014 09:43:58 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	swarren@...dia.com, wsa@...-dreams.de, abrestic@...omium.org,
	dgreid@...omium.org, olof@...om.net, sjg@...omium.org,
	linux-samsung-soc@...r.kernel.org, linux-tegra@...r.kernel.org,
	David Hendricks <dhendrix@...omium.org>, sameo@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/7] mfd: cros_ec: spi: calculate delay between
 transfers correctly

> From: David Hendricks <dhendrix@...omium.org>
> 
> To avoid spamming the EC we calculate the time between the previous
> transfer and the current transfer and force a delay if the time delta
> is too small.
> 
> However, a small miscalculation causes the delay period to be
> far too short. Most noticably this impacts commands with a long
> turnaround time such as EC firmware reads and writes.
> 
> Signed-off-by: David Hendricks <dhendrix@...omium.org>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> Acked-by: Lee Jones <lee.jones@...aro.org>
> Reviewed-by: Simon Glass <sjg@...omium.org>
> Tested-by: Andrew Bresticker <abrestic@...omium.org>
> Tested-by: Stephen Warren <swarren@...dia.com>
> ---
> Changes in v3: None
> Changes in v2: None
> 
>  drivers/mfd/cros_ec_spi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

> diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
> index 84af8d7..c185eb6 100644
> --- a/drivers/mfd/cros_ec_spi.c
> +++ b/drivers/mfd/cros_ec_spi.c
> @@ -219,7 +219,7 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
>  		ktime_get_ts(&ts);
>  		delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns;
>  		if (delay < EC_SPI_RECOVERY_TIME_NS)
> -			ndelay(delay);
> +			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
>  	}
>  
>  	/* Transmit phase - send our message */

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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