linux-kernel - [PATCH 1/3] PM / devfreq: Actually support providing freq

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Date:   Mon, 23 Apr 2018 17:20:14 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Vinayak Holikatti <vinholikatti@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: [PATCH 1/3] PM / devfreq: Actually support providing freq_table

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 <bjorn.andersson@...aro.org>
---

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];
 }

 static unsigned long find_available_max_freq(struct devfreq *devfreq)
 {
-	struct dev_pm_opp *opp;
-	unsigned long max_freq = ULONG_MAX;
-
-	opp = dev_pm_opp_find_freq_floor(devfreq->dev.parent, &max_freq);
-	if (IS_ERR(opp))
-		max_freq = 0;
-	else
-		dev_pm_opp_put(opp);
+	struct devfreq_dev_profile *profile = devfreq->profile;

-	return max_freq;
+	return profile->freq_table[profile->max_state - 1];
 }

 /**
-- 
2.16.2