On 2014/10/16 17:34, Mark Brown wrote:
> On Thu, Oct 16, 2014 at 05:16:02PM +0800, addy ke wrote:
>> On 2014/10/15 21:04, Mark Brown wrote:
>>> On Wed, Oct 15, 2014 at 07:25:49PM +0800, Addy Ke wrote:
>
>>>> + if (WARN_ON(rs->speed > MAX_SCLK_OUT))
>>>> + rs->speed = MAX_SCLK_OUT;
>
>>>> + /* the minimum divsor is 2 */
>>>> + if (rs->max_freq < 2 * rs->speed) {
>>>> + clk_set_rate(rs->spiclk, 2 * rs->speed);
>>>> + rs->max_freq = clk_get_rate(rs->spiclk);
>>>> + }
>
>>> I'll apply this but you should be checking the return code from
>>> clk_set_rate() here, please send a followup patch doing that. It might
>
>> If clk_set_rate return error, do I only put dev_warn here or return error
>> value to spi core?
>
> It'd be better to return an error if we need to set the rate and can't
> do it.
>
>>> also be worth consdering just setting the rate unconditionally here, it
>>> seems like it should make things simpler.
>
>> I think we need.
>> If we set the rate unconditionally here, clk_set_rate() will be executed in
>> each spi transfer.
>
> Is that really such a high cost?
>
Not high cost, but I think if the default spi_clk is enough, we do not need to
set spi_clk again.
Maybe we can only set spi_clk as (2 * MAX_SCLK_OUT) in probe().
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