cpufreq: qcom: Implement clk_ops::determine_rate() for qcom_cpufreq* clocks

determine_rate() callback is used by the clk_set_rate() API to get the
closest rate of the target rate supported by the clock. If this callback
is not implemented (nor round_rate() callback), then the API will assume
that the clock cannot set the requested rate. And since there is no parent,
it will return -EINVAL.

This is not an issue right now as clk_set_rate() mistakenly compares the
target rate with cached rate and bails out early. But once that is fixed
to compare the target rate with the actual rate of the clock (returned by
recalc_rate()), then clk_set_rate() for this clock will start to fail as
below:

cpu cpu0: _opp_config_clk_single: failed to set clock rate: -22

So implement the determine_rate() callback that just returns the actual
rate at which the clock is passed to the CPUs in a domain.

Fixes: 4370232 ("cpufreq: qcom-hw: Add CPU clock provider support")
Reported-by: Johan Hovold <johan+linaro@kernel.org>
Suggested-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: Mani-Sadhasivam

drivers/cpufreq/qcom-cpufreq-hw.c

@@ -626,8 +626,21 @@ static unsigned long qcom_cpufreq_hw_recalc_rate(struct clk_hw *hw, unsigned lon
 	return __qcom_cpufreq_hw_get(data->policy) * HZ_PER_KHZ;
 }
 
+/*
+ * Since we cannot determine the closest rate of the target rate, let's just
+ * return the actual rate at which the clock is running at. This is needed to
+ * make clk_set_rate() API work properly.
+ */
+static int qcom_cpufreq_hw_determine_rate(struct clk_hw *hw, struct clk_rate_request *req)
+{
+	req->rate = qcom_cpufreq_hw_recalc_rate(hw, 0);
+
+	return 0;
+}
+
 static const struct clk_ops qcom_cpufreq_hw_clk_ops = {
 	.recalc_rate = qcom_cpufreq_hw_recalc_rate,
+	.determine_rate = qcom_cpufreq_hw_determine_rate,
 };
 
 static int qcom_cpufreq_hw_driver_probe(struct platform_device *pdev)