linux-kernel - Re: [PATCH] spi: s3c64xx: do not disable the clock while configuring the spi

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Date:	Thu, 07 Jul 2016 11:41:49 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Andi Shyti <andi.shyti@...sung.com>,
	Mark Brown <broonie@...nel.org>
Cc:	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andi Shyti <andi@...zian.org>
Subject: Re: [PATCH] spi: s3c64xx: do not disable the clock while configuring
 the spi

On 07/07/2016 09:23 AM, Andi Shyti wrote:
> When the clock is coming from the cmu it is not required to be
> disabled and then re-enabled in order to change the rate.
> 
> Besides, some exynos chipsets (e.g. exynos5433) do not deliver
> any to the SFR if one from the pclk ("spi" in this case) or sclk
> ("busclk") is disabled.
> 
> Remove the clock disabling/enabling to avoid falling into this
> situation.
> 
> Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
> Signed-off-by: Andi Shyti <andi.shyti@...sung.com>
> ---
> 
> Hi,
> 
> This patch has been tested by me and Sylwester on Trats2
> (exynos4412) and tm2(e) (exynos5433) boards, for big data
> (which use dma transfer) and small data.
> 
> It also fixes in exynos5433 a synchronus abort caused by the fact
> that the pclk (spi) doesn't get delivered if the sclk is disabled
> (busclk)
> 
> Thanks,
> Andi
> 
>  drivers/spi/spi-s3c64xx.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Best regards,
Krzysztof