From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Andersson Subject: Re: [PATCH 1/3] PM / devfreq: Actually support providing freq_table Date: Mon, 23 Apr 2018 22:29:16 -0700 Message-ID: <20180424052916.GD2052@tuxbook-pro> References: <20180424002016.9205-1-bjorn.andersson@linaro.org> <20180424002016.9205-2-bjorn.andersson@linaro.org> <5ADE9AE6.9090601@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <5ADE9AE6.9090601@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Chanwoo Choi Cc: MyungJoo Ham , Kyungmin Park , Vinayak Holikatti , "James E.J. Bottomley" , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Vivek Gautam List-Id: linux-pm@vger.kernel.org On Mon 23 Apr 19:48 PDT 2018, Chanwoo Choi wrote: > Hi, > > On 2018??? 04??? 24??? 09:20, Bjorn Andersson wrote: > > The code in devfreq_add_device() handles the case where a freq_table is > > passed by the client, but then requests min and max frequences from > > the, in this case absent, opp tables. > > > > Read the min and max frequencies from the frequency table, which has > > been built from the opp table if one exists, instead of querying the > > opp table. > > > > Signed-off-by: Bjorn Andersson > > --- > > > > An alternative approach is to clarify in the devfreq code that it's not > > possible to pass a freq_table and then in patch 3 create an opp table for the > > device in runtime; although the error handling of this becomes non-trivial. > > > > Transitioning the UFSHCD to use opp tables directly is hindered by the fact > > that the Qualcomm UFS hardware has two different clocks that needs to be > > running at different rates, so we would need a way to describe the two rates in > > the opp table. (And would force us to change the DT binding) > > > > drivers/devfreq/devfreq.c | 22 ++++------------------ > > 1 file changed, 4 insertions(+), 18 deletions(-) > > > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > > index fe2af6aa88fc..086ced50a13d 100644 > > --- a/drivers/devfreq/devfreq.c > > +++ b/drivers/devfreq/devfreq.c > > @@ -74,30 +74,16 @@ static struct devfreq *find_device_devfreq(struct device *dev) > > > > static unsigned long find_available_min_freq(struct devfreq *devfreq) > > { > > - struct dev_pm_opp *opp; > > - unsigned long min_freq = 0; > > - > > - opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &min_freq); > > - if (IS_ERR(opp)) > > - min_freq = 0; > > - else > > - dev_pm_opp_put(opp); > > + struct devfreq_dev_profile *profile = devfreq->profile; > > > > - return min_freq; > > + return profile->freq_table[0]; > > It is wrong. The thermal framework support the devfreq-cooling device > which uses the dev_pm_opp_enable/disable(). > Okay, that makes sense. So rather than registering a custom freq_table I should register the min and max frequency using dev_pm_opp_add(). > In order to find the correct available min frequency, > the devfreq have to use the OPP function instead of using the first entry > of the freq_table array. > Based on this there seems to be room for cleaning out the freq_table from devfreq, to reduce the confusion. I will review this further. Thanks, Bjorn