Hi,
On Mon, Jul 11, 2011 at 10:26 PM, Wolfram Sang <w.sang@xxxxxxxxxxxxxx> wrote:
> Hi Koen,
>
> thanks for v2.
>
> On Mon, Jul 11, 2011 at 09:52:01PM +0200, Koen Beel wrote:
>
>> (Sorry, patch in attachment as I still don't have a decent mail setup
>> at my company)
>
> That's bad :(
>
> ====
>
>> Fix clock rate setting on mxs-mmc driver.
>> Previously, if div2 was zero the value for TIMING_CLOCK_RATE would
>> have been 255 instead of 0.
>> Also the limits for div1 (TIMING_CLOCK_DIVIDE) and div2
>> (TIMING_CLOCK_RATE + 1) where not correctly defined.
>
> Very minor nit: No paragraphs I'd say.
>
>> Can easily be reproduced on mx23evk: default clock for high speed sdio
>> cards is 50 MHz. With a SSP_CLK of 28.8 MHz default), this resulted in
>> an actual clock rate of about 56 kHz.
>> Tested on mx23evk.
>>
>> Changes in V2 patch:
>> - use DIV_ROUND_UP to make sure the actual clock rate is not higher
>> then the requested clock rate.
>> - rename variables to reflect naming in datasheet and to make things
>> more clear
>
> Changelogs are good, but should go below "---"
>
>>
>> Signed-off-by: Koen Beel <koen.beel@xxxxxxxxx>
>> ---
>> drivers/mmc/host/mxs-mmc.c | 30 ++++++++++++++----------------
>> 1 files changed, 14 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
>> index 99d39a6..d513d47 100644
>> --- a/drivers/mmc/host/mxs-mmc.c
>> +++ b/drivers/mmc/host/mxs-mmc.c
>> @@ -564,40 +564,38 @@ static void mxs_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
>>
>> static void mxs_mmc_set_clk_rate(struct mxs_mmc_host *host, unsigned int rate)
>> {
>> - unsigned int ssp_rate, bit_rate;
>> - u32 div1, div2;
>> + unsigned int ssp_clk, ssp_sck;
>
> ssp_sck is not really needed? Value could directly go to host->clk_rate.
>
>> + u32 clock_divide, clock_rate;
>> u32 val;
>>
>> - ssp_rate = clk_get_rate(host->clk);
>> + ssp_clk = clk_get_rate(host->clk);
>>
>> - for (div1 = 2; div1 < 254; div1 += 2) {
>> - div2 = ssp_rate / rate / div1;
>> - if (div2 < 0x100)
>> + for (clock_divide = 2; clock_divide <= 254; clock_divide += 2) {
>> + clock_rate = DIV_ROUND_UP(ssp_clk, rate * clock_divide);
>> + clock_rate = (clock_rate > 0) ? clock_rate - 1 : 0;
>> + if (clock_rate <= 255)
>> break;
>> }
>>
>> - if (div1 >= 254) {
>> + if (clock_divide > 254) {
>> dev_err(mmc_dev(host->mmc),
>> "%s: cannot set clock to %d\n", __func__, rate);
>
> Didn't you want to set some minimal values instead of just returning?
> Just wondering, could be a seperate patch in my book...
>
>> return;
>> }
>>
>> - if (div2 == 0)
>> - bit_rate = ssp_rate / div1;
>> - else
>> - bit_rate = ssp_rate / div1 / div2;
>> + ssp_sck = ssp_clk / clock_divide / (1 + clock_rate);
>>
>> val = readl(host->base + HW_SSP_TIMING);
>> val &= ~(BM_SSP_TIMING_CLOCK_DIVIDE | BM_SSP_TIMING_CLOCK_RATE);
>> - val |= BF_SSP(div1, TIMING_CLOCK_DIVIDE);
>> - val |= BF_SSP(div2 - 1, TIMING_CLOCK_RATE);
>> + val |= BF_SSP(clock_divide, TIMING_CLOCK_DIVIDE);
>> + val |= BF_SSP(clock_rate, TIMING_CLOCK_RATE);
>> writel(val, host->base + HW_SSP_TIMING);
>>
>> - host->clk_rate = bit_rate;
>> + host->clk_rate = ssp_sck;
>>
>> dev_dbg(mmc_dev(host->mmc),
>> - "%s: div1 %d, div2 %d, ssp %d, bit %d, rate %d\n",
>> - __func__, div1, div2, ssp_rate, bit_rate, rate);
>> + "%s: clock_divide %d, clock_rate %d, ssp_clk %d, rate_actual %d, rate_requested %d\n",
>> + __func__, clock_divide, clock_rate, ssp_clk, ssp_sck, rate);
>> }
>>
>
> Rest looks good to me, and test was also successful.
>
> Chris, if you want to take this version already:
Still need me to do something on this or is it ok?
Koen
>
> Reviewed-by: Wolfram Sang <w.sang@xxxxxxxxxxxxxx>
>
> --
> Pengutronix e.K. | Wolfram Sang |
> Industrial Linux Solutions | http://www.pengutronix.de/ |
>
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