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SubjectRe: [PATCH v2 7/9] spi: spi-s3c64xx: Ensure cur_speed holds actual clock value
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It was <2020-08-22 sob 14:43>, when Krzysztof Kozlowski wrote:
> On Fri, Aug 21, 2020 at 06:13:59PM +0200, Łukasz Stelmach wrote:
>> cur_speed is used to calculate transfer timeout and needs to be
>> set to the actual value of (half) the clock speed for precise
>> calculations.
>
> If you need this only for timeout calculation just divide it in
> s3c64xx_wait_for_dma().

I divide it here to keep the relationship between the value the variable
holds and the one that is inside clk_* (See? It's multiplied 3 lines
above). If you look around every single clk_get_rate() call in the file is
divided by two.

> Otherwise why only if (cmu) case is updated?

You are righ I will update that too.

However, I wonder if it is even possible that the value read from
S3C64XX_SPI_CLK_CFG would be different than the one written to it?

> You are also affecting here not only timeout but
> s3c64xx_enable_datapath() which is not mentioned in commit log. In other
> words, this looks wrong.

Indeed, there is a reference too. I've corrected the message.

>>
>> Cc: Tomasz Figa <tfiga@chromium.org>
>> Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
>> ---
>> drivers/spi/spi-s3c64xx.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index 02de734b8ab1..89c162efe355 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -626,6 +626,7 @@ static int s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
>> ret = clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);
>> if (ret)
>> return ret;
>> + sdd->cur_speed = clk_get_rate(sdd->src_clk) / 2;
>> } else {
>> /* Configure Clock */
>> val = readl(regs + S3C64XX_SPI_CLK_CFG);
>> --
>> 2.26.2
>>
>
>

--
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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