Re: [PATCH v1 3/5] PM / devfreq: tegra20: Use clk_round_rate_unboundly()

[Chanwoo Choi]

On 4/1/20 8:22 AM, Chanwoo Choi wrote:
> Hi Dmitry,
> 
> On 3/31/20 8:16 AM, Dmitry Osipenko wrote:
>> The clk_round_rate() doesn't work for us properly if clock rate is bounded
>> by a min/max rate that is requested by some other clk-user because we're
>> building devfreq's OPP table based on the rounding.
>>
>> In particular this becomes a problem if display driver is probed earlier
>> than devfreq, and thus, display adds a memory bandwidth request using
>> interconnect API, which results in a minimum clock-rate being set for
>> the memory clk. In a result, the lowest devfreq OPP rate is getting
>> limited to the minimum rate imposed by the display driver.
>>
>> Let's use new clk_round_rate_unboundly() that resolves the problem by
>> rounding clock rate without taking into account min/max limits imposed by
>> active clk users.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>> ---
>>  drivers/devfreq/tegra20-devfreq.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/devfreq/tegra20-devfreq.c b/drivers/devfreq/tegra20-devfreq.c
>> index ff82bac9ee4e..1bb10ef11dfe 100644
>> --- a/drivers/devfreq/tegra20-devfreq.c
>> +++ b/drivers/devfreq/tegra20-devfreq.c
>> @@ -149,10 +149,10 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>>  
>>  	tegra->regs = mc->regs;
>>  
>> -	max_rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
>> +	max_rate = clk_round_rate_unboundly(tegra->emc_clock, ULONG_MAX);
>>  
>>  	for (rate = 0; rate <= max_rate; rate++) {
>> -		rate = clk_round_rate(tegra->emc_clock, rate);
>> +		rate = clk_round_rate_unboundly(tegra->emc_clock, rate);
>>  
>>  		err = dev_pm_opp_add(&pdev->dev, rate, 0);
>>  		if (err) {
>>
> 
> Firstly, patch1 have to be reviewed for this patch.
> I have no any objection. It looks good to me.
> 
> If patch1 get the confirmation from clock maintainer,
> feel free to add my acked tag:
> Acked-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
> 

Sorry. I mean the patch2 about clk_round_rate_unboundly() function.
instead of patch1. 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics