[PATCH] ARM: smp_twd: reprogram twd based on clk notifier
From: Stephen Warren <hidden>
Date: 2012-09-12 20:47:13
On 09/07/2012 02:19 AM, Shawn Guo wrote:
From: Mike Turquette <redacted> Running cpufreq driver on imx6q, the following warning is seen. $ BUG: sleeping function called from invalid context at kernel/mutex.c:269
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It looks that the warning is caused by that twd_update_frequency() gets called from an atomic context while it calls clk_get_rate() where a mutex gets held. To fix the warning, let's convert the existing code to use clk notifiers in place of CPUfreq notifiers. This works out nicely for Cortex-A9 MPcore designs that scale all CPUs at the same frequency. Signed-off-by: Mike Turquette <redacted> Signed-off-by: Shawn Guo <redacted>
At least in next-20120912, this doesn't appear to cause any issue on either Tegra20 or Tegra30. I'm copying Prashant to verify this is OK for Tegra. For reference, the situation for Tegra is: Pre-3.7: Tegra20: Does not use common clock, and there is NO "smp_twd" clock defined. Tegra30: Does not use common clock, and there IS a "smp_twd" clock defined. In 3.7 will be: Tegra20: Supports common clock, but there is NO "smp_twd" clock defined. Tegra30: Supports common clock, and there IS a "smp_twd" clock defined. I believe Prashant will be sending a patch very soon to define an "smp_twd" clock for Tegra20. The Tegra cpufreq driver currently only initializes on Tegra20 and not Tegra30 right now due to some clock-naming differences. I don't expect this to change in 3.7, but who knows, someone might send a patch in the next 2 days or so...
quoted hunk ↗ jump to hunk
--- arch/arm/kernel/smp_twd.c | 32 +++++++++++++------------------- 1 files changed, 13 insertions(+), 19 deletions(-)diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c index fef42b2..635e3ea 100644 --- a/arch/arm/kernel/smp_twd.c +++ b/arch/arm/kernel/smp_twd.c@@ -11,7 +11,6 @@ #include <linux/init.h> #include <linux/kernel.h> #include <linux/clk.h> -#include <linux/cpufreq.h> #include <linux/delay.h> #include <linux/device.h> #include <linux/err.h>@@ -96,51 +95,46 @@ static void twd_timer_stop(struct clock_event_device *clk) disable_percpu_irq(clk->irq); } -#ifdef CONFIG_CPU_FREQ - /* * Updates clockevent frequency when the cpu frequency changes. * Called on the cpu that is changing frequency with interrupts disabled. */ -static void twd_update_frequency(void *data) +static void twd_update_frequency(void *new_rate) { - twd_timer_rate = clk_get_rate(twd_clk); + twd_timer_rate = *((unsigned long *) new_rate); clockevents_update_freq(*__this_cpu_ptr(twd_evt), twd_timer_rate); } -static int twd_cpufreq_transition(struct notifier_block *nb, - unsigned long state, void *data) +static int twd_rate_change(struct notifier_block *nb, + unsigned long flags, void *data) { - struct cpufreq_freqs *freqs = data; + struct clk_notifier_data *cnd = data; /* * The twd clock events must be reprogrammed to account for the new * frequency. The timer is local to a cpu, so cross-call to the * changing cpu. */ - if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE) - smp_call_function_single(freqs->cpu, twd_update_frequency, - NULL, 1); + if (flags == POST_RATE_CHANGE) + smp_call_function(twd_update_frequency, + (void *)&cnd->new_rate, 1); return NOTIFY_OK; } -static struct notifier_block twd_cpufreq_nb = { - .notifier_call = twd_cpufreq_transition, +static struct notifier_block twd_clk_nb = { + .notifier_call = twd_rate_change, }; -static int twd_cpufreq_init(void) +static int twd_clk_init(void) { if (twd_evt && *__this_cpu_ptr(twd_evt) && !IS_ERR(twd_clk)) - return cpufreq_register_notifier(&twd_cpufreq_nb, - CPUFREQ_TRANSITION_NOTIFIER); + return clk_notifier_register(twd_clk, &twd_clk_nb); return 0; } -core_initcall(twd_cpufreq_init); - -#endif +core_initcall(twd_clk_init); static void __cpuinit twd_calibrate_rate(void) {