opp: Don't overwrite rounded clk rate

The OPP table normally contains 'fmax' values corresponding to the
voltage or performance levels of each OPP, but we don't necessarily want
all the devices to run at fmax all the time. Running at fmax makes sense
for devices like CPU/GPU, which have a finite amount of work to do and
since a specific amount of energy is consumed at an OPP, its better to
run at the highest possible frequency for that voltage value.

On the other hand, we have IO devices which need to run at specific
frequencies only for their proper functioning, instead of maximum
possible frequency.

The OPP core currently roundup to the next possible OPP for a frequency
and select the fmax value. To support the IO devices by the OPP core,
lets do the roundup to fetch the voltage or performance state values,
but not use the OPP frequency value. Rather use the value returned by
clk_round_rate().

The current user, cpufreq, of dev_pm_opp_set_rate() already does the
rounding to the next OPP before calling this routine and it won't
have any side affects because of this change.
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
[ Viresh: Massaged changelog, added comment and use temp_opp variable
	  instead ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/core.c

@@ -751,13 +751,16 @@ static int _set_required_opps(struct device *dev,
  * @dev:	 device for which we do this operation
  * @target_freq: frequency to achieve
  *
- * This configures the power-supplies and clock source to the levels specified
- * by the OPP corresponding to the target_freq.
+ * This configures the power-supplies to the levels specified by the OPP
+ * corresponding to the target_freq, and programs the clock to a value <=
+ * target_freq, as rounded by clk_round_rate(). Device wanting to run at fmax
+ * provided by the opp, should have already rounded to the target OPP's
+ * frequency.
  */
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 {
 	struct opp_table *opp_table;
-	unsigned long freq, old_freq;
+	unsigned long freq, old_freq, temp_freq;
 	struct dev_pm_opp *old_opp, *opp;
 	struct clk *clk;
 	int ret;
@@ -796,13 +799,15 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 		goto put_opp_table;
 	}
 
-	old_opp = _find_freq_ceil(opp_table, &old_freq);
+	temp_freq = old_freq;
+	old_opp = _find_freq_ceil(opp_table, &temp_freq);
 	if (IS_ERR(old_opp)) {
 		dev_err(dev, "%s: failed to find current OPP for freq %lu (%ld)\n",
 			__func__, old_freq, PTR_ERR(old_opp));
 	}
 
-	opp = _find_freq_ceil(opp_table, &freq);
+	temp_freq = freq;
+	opp = _find_freq_ceil(opp_table, &temp_freq);
 	if (IS_ERR(opp)) {
 		ret = PTR_ERR(opp);
 		dev_err(dev, "%s: failed to find OPP for freq %lu (%d)\n",