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authorLinus Walleij <linus.walleij@linaro.org>2012-10-23 08:29:48 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-11-04 10:31:02 +0000
commita68becd1dcda55b467dcabaff136cadc10abb761 (patch)
tree5340a006f3a058b5aa1f40c81bbadcb50c762295 /arch/arm/kernel/smp_twd.c
parent2577cf246233b1e4e38576f28a5ec05c9c6a6c2a (diff)
downloadop-kernel-dev-a68becd1dcda55b467dcabaff136cadc10abb761.zip
op-kernel-dev-a68becd1dcda55b467dcabaff136cadc10abb761.tar.gz
ARM: 7563/1: SMP_TWD: make setup()/stop() reentrant
It has been brought to my knowledge that the .setup()/.stop() function pair in the SMP TWD is going to be called from atomic contexts for CPUs coming and going, and then the clk_prepare()/clk_unprepare() calls cannot be called on subsequent .setup()/.stop() iterations. This is however just the tip of an iceberg as the function pair is not designed to be reentrant at all. This change makes the SMP_TWD clock .setup()/.stop() pair reentrant by splitting the .setup() function in three parts: - One COMMON part that is executed the first time the first CPU in the TWD cluster is initialized. This will fetch the TWD clk for the cluster and prepare+enable it. If no clk is available it will calibrate the rate instead. - One part that is executed the FIRST TIME a certain CPU is brought on-line. This initializes and sets up the clock event for a certain CPU. - One part that is executed on every subsequent .setup() call. This will re-initialize the clock event. This is augmented to call the clk_enable()/clk_disable() pair properly. Cc: Shawn Guo <shawn.guo@linaro.org> Reported-by: Peter Chen <peter.chen@freescale.com> Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Tested-by: Shawn Guo <shawn.guo@linaro.org> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/smp_twd.c')
-rw-r--r--arch/arm/kernel/smp_twd.c42
1 files changed, 37 insertions, 5 deletions
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 780b057..a2e7437 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -31,6 +31,8 @@ static void __iomem *twd_base;
static struct clk *twd_clk;
static unsigned long twd_timer_rate;
+static bool common_setup_called;
+static DEFINE_PER_CPU(bool, percpu_setup_called);
static struct clock_event_device __percpu **twd_evt;
static int twd_ppi;
@@ -264,15 +266,45 @@ static struct clk *twd_get_clock(void)
static int __cpuinit twd_timer_setup(struct clock_event_device *clk)
{
struct clock_event_device **this_cpu_clk;
+ int cpu = smp_processor_id();
- if (!twd_clk)
+ /*
+ * If the basic setup for this CPU has been done before don't
+ * bother with the below.
+ */
+ if (per_cpu(percpu_setup_called, cpu)) {
+ __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
+ clockevents_register_device(*__this_cpu_ptr(twd_evt));
+ enable_percpu_irq(clk->irq, 0);
+ return 0;
+ }
+ per_cpu(percpu_setup_called, cpu) = true;
+
+ /*
+ * This stuff only need to be done once for the entire TWD cluster
+ * during the runtime of the system.
+ */
+ if (!common_setup_called) {
twd_clk = twd_get_clock();
- if (!IS_ERR_OR_NULL(twd_clk))
- twd_timer_rate = clk_get_rate(twd_clk);
- else
- twd_calibrate_rate();
+ /*
+ * We use IS_ERR_OR_NULL() here, because if the clock stubs
+ * are active we will get a valid clk reference which is
+ * however NULL and will return the rate 0. In that case we
+ * need to calibrate the rate instead.
+ */
+ if (!IS_ERR_OR_NULL(twd_clk))
+ twd_timer_rate = clk_get_rate(twd_clk);
+ else
+ twd_calibrate_rate();
+
+ common_setup_called = true;
+ }
+ /*
+ * The following is done once per CPU the first time .setup() is
+ * called.
+ */
__raw_writel(0, twd_base + TWD_TIMER_CONTROL);
clk->name = "local_timer";
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