cpufreq: Tegra: implement intermediate frequency callbacks

Tegra has been switching to intermediate frequency (pll_p_clk) forever.
CPUFreq core has better support for handling notifications for these
frequencies and so we can adapt Tegra's driver to it.

Also do a WARN() if clk_set_parent() fails while moving back to pll_x
as we should have atleast restored to earlier frequency on error.

Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/tegra-cpufreq.c b/drivers/cpufreq/tegra-cpufreq.c
index 6e774c6ac20bf3ab82fe0e0dc3bd204de04009f9..a5fbc0a8d897bc7727ba32c176d255a8093c02f0 100644 (file)
--- a/drivers/cpufreq/tegra-cpufreq.c
+++ b/drivers/cpufreq/tegra-cpufreq.c
@@ -45,46 +45,51 @@ static struct clk *cpu_clk;
 static struct clk *pll_x_clk;
 static struct clk *pll_p_clk;
 static struct clk *emc_clk;
+static bool pll_x_prepared;
 
-static int tegra_cpu_clk_set_rate(unsigned long rate)
+static unsigned int tegra_get_intermediate(struct cpufreq_policy *policy,
+                                          unsigned int index)
+{
+       unsigned int ifreq = clk_get_rate(pll_p_clk) / 1000;
+
+       /*
+        * Don't switch to intermediate freq if:
+        * - we are already at it, i.e. policy->cur == ifreq
+        * - index corresponds to ifreq
+        */
+       if ((freq_table[index].frequency == ifreq) || (policy->cur == ifreq))
+               return 0;
+
+       return ifreq;
+}
+
+static int tegra_target_intermediate(struct cpufreq_policy *policy,
+                                    unsigned int index)
 {
        int ret;
 
        /*
         * Take an extra reference to the main pll so it doesn't turn
-        * off when we move the cpu off of it
+        * off when we move the cpu off of it as enabling it again while we
+        * switch to it from tegra_target() would take additional time. Though
+        * when target-freq is intermediate freq, we don't need to take this
+        * reference.
         */
        clk_prepare_enable(pll_x_clk);
 
        ret = clk_set_parent(cpu_clk, pll_p_clk);
-       if (ret) {
-               pr_err("Failed to switch cpu to clock pll_p\n");
-               goto out;
-       }
-
-       if (rate == clk_get_rate(pll_p_clk))
-               goto out;
-
-       ret = clk_set_rate(pll_x_clk, rate);
-       if (ret) {
-               pr_err("Failed to change pll_x to %lu\n", rate);
-               goto out;
-       }
-
-       ret = clk_set_parent(cpu_clk, pll_x_clk);
-       if (ret) {
-               pr_err("Failed to switch cpu to clock pll_x\n");
-               goto out;
-       }
+       if (ret)
+               clk_disable_unprepare(pll_x_clk);
+       else
+               pll_x_prepared = true;
 
-out:
-       clk_disable_unprepare(pll_x_clk);
        return ret;
 }
 
 static int tegra_target(struct cpufreq_policy *policy, unsigned int index)
 {
        unsigned long rate = freq_table[index].frequency;
+       unsigned int ifreq = clk_get_rate(pll_p_clk) / 1000;
        int ret = 0;
 
        /*
@@ -98,10 +103,30 @@ static int tegra_target(struct cpufreq_policy *policy, unsigned int index)
        else
                clk_set_rate(emc_clk, 100000000);  /* emc 50Mhz */
 
-       ret = tegra_cpu_clk_set_rate(rate * 1000);
+       /*
+        * target freq == pll_p, don't need to take extra reference to pll_x_clk
+        * as it isn't used anymore.
+        */
+       if (rate == ifreq)
+               return clk_set_parent(cpu_clk, pll_p_clk);
+
+       ret = clk_set_rate(pll_x_clk, rate * 1000);
+       /* Restore to earlier frequency on error, i.e. pll_x */
        if (ret)
-               pr_err("cpu-tegra: Failed to set cpu frequency to %lu kHz\n",
-                       rate);
+               pr_err("Failed to change pll_x to %lu\n", rate);
+
+       ret = clk_set_parent(cpu_clk, pll_x_clk);
+       /* This shouldn't fail while changing or restoring */
+       WARN_ON(ret);
+
+       /*
+        * Drop count to pll_x clock only if we switched to intermediate freq
+        * earlier while transitioning to a target frequency.
+        */
+       if (pll_x_prepared) {
+               clk_disable_unprepare(pll_x_clk);
+               pll_x_prepared = false;
+       }
 
        return ret;
 }
@@ -137,16 +162,18 @@ static int tegra_cpu_exit(struct cpufreq_policy *policy)
 }
 
 static struct cpufreq_driver tegra_cpufreq_driver = {
-       .flags          = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
-       .verify         = cpufreq_generic_frequency_table_verify,
-       .target_index   = tegra_target,
-       .get            = cpufreq_generic_get,
-       .init           = tegra_cpu_init,
-       .exit           = tegra_cpu_exit,
-       .name           = "tegra",
-       .attr           = cpufreq_generic_attr,
+       .flags                  = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+       .verify                 = cpufreq_generic_frequency_table_verify,
+       .get_intermediate       = tegra_get_intermediate,
+       .target_intermediate    = tegra_target_intermediate,
+       .target_index           = tegra_target,
+       .get                    = cpufreq_generic_get,
+       .init                   = tegra_cpu_init,
+       .exit                   = tegra_cpu_exit,
+       .name                   = "tegra",
+       .attr                   = cpufreq_generic_attr,
 #ifdef CONFIG_PM
-       .suspend        = cpufreq_generic_suspend,
+       .suspend                = cpufreq_generic_suspend,
 #endif
 };