[PATCH V4 3/3] cpufreq: Tegra: implement intermediate frequency callbacks

Viresh Kumar
2014-05-21T09:05:03Z

Tegra had always been switching to intermediate frequency (pll_p_clk) since
ever. 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.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/cpufreq/tegra-cpufreq.c | 81 ++++++++++++++++++++++++-----------------
1 file changed, 47 insertions(+), 34 deletions(-)

diff --git a/drivers/cpufreq/tegra-cpufreq.c b/drivers/cpufreq/tegra-cpufreq.c
index 6e774c6..a64b970 100644
--- a/drivers/cpufreq/tegra-cpufreq.c
+++ b/drivers/cpufreq/tegra-cpufreq.c
@@ -46,7 +46,24 @@ static struct clk *pll_x_clk;
static struct clk *pll_p_clk;
static struct clk *emc_clk;

-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;

@@ -57,28 +74,9 @@ static int tegra_cpu_clk_set_rate(unsigned long rate)
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);

-out:
- clk_disable_unprepare(pll_x_clk);
return ret;
}

@@ -98,10 +96,23 @@ 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 */
+ if (rate * 1000 == clk_get_rate(pll_p_clk)) {
+ ret = tegra_target_intermediate(policy, index);
+ goto disable_pll_x;
+ }
+
+ 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);
+
+disable_pll_x:
+ clk_disable_unprepare(pll_x_clk);

return ret;
}
@@ -137,16 +148,18 @@ 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
};

--
2.0.0.rc2