[PATCH v2 5/7] ARM: B15: Add suspend/resume hooks

From: Florian Fainelli
Date: Fri Jun 23 2017 - 13:53:48 EST


The Broadcom Brahma-B15 CPU readahead cache registers will be restored
to their Power-on-Reset values after a S3 suspend/resume cycles, so we
want to restore what we had enabled before.

Another thing we want to take care of is disabling the read-ahead cache
prior to suspending to avoid any sort of side effect with the spinlock
we need to grab to serialize register accesses.

Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
---
arch/arm/mm/cache-b15-rac.c | 48 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)

diff --git a/arch/arm/mm/cache-b15-rac.c b/arch/arm/mm/cache-b15-rac.c
index d85b63211759..9ee1d89cced0 100644
--- a/arch/arm/mm/cache-b15-rac.c
+++ b/arch/arm/mm/cache-b15-rac.c
@@ -15,6 +15,7 @@
#include <linux/of_address.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
+#include <linux/syscore_ops.h>

#include <asm/cacheflush.h>
#include <asm/hardware/cache-b15-rac.h>
@@ -41,6 +42,10 @@ extern void v7_flush_kern_cache_all(void);
RACENPREF_MASK << RACENDATA_SHIFT)

#define RAC_ENABLED 0
+/* Special state where we want to bypass the spinlock and call directly
+ * into the v7 cache maintenance operations during suspend/resume
+ */
+#define RAC_SUSPENDED 1

static void __iomem *b15_rac_base;
static DEFINE_SPINLOCK(rac_lock);
@@ -96,6 +101,12 @@ void b15_flush_##name(void) \
unsigned int do_flush; \
u32 val = 0; \
\
+ if (test_bit(RAC_SUSPENDED, &b15_rac_flags)) { \
+ v7_flush_##name(); \
+ bar; \
+ return; \
+ } \
+ \
spin_lock(&rac_lock); \
do_flush = test_bit(RAC_ENABLED, &b15_rac_flags); \
if (do_flush) \
@@ -208,6 +219,39 @@ static int b15_rac_dead_cpu(unsigned int cpu)
}
#endif /* CONFIG_HOTPLUG_CPU */

+#ifdef CONFIG_PM_SLEEP
+static int b15_rac_suspend(void)
+{
+ /* Suspend the read-ahead cache oeprations, forcing our cache
+ * implementation to fallback to the regular ARMv7 calls.
+ *
+ * We are guaranteed to be running on the boot CPU at this point and
+ * with every other CPU quiesced, so setting RAC_SUSPENDED is not racy
+ * here.
+ */
+ rac_config0_reg = b15_rac_disable_and_flush();
+ set_bit(RAC_SUSPENDED, &b15_rac_flags);
+
+ return 0;
+}
+
+static void b15_rac_resume(void)
+{
+ /* Coming out of a S3 suspend/resume cycle, the read-ahead cache
+ * register RAC_CONFIG0_REG will be restored to its default value, make
+ * sure we re-enable it and set the enable flag, we are also guaranteed
+ * to run on the boot CPU, so not racy again.
+ */
+ __b15_rac_enable(rac_config0_reg);
+ clear_bit(RAC_SUSPENDED, &b15_rac_flags);
+}
+
+static struct syscore_ops b15_rac_syscore_ops = {
+ .suspend = b15_rac_suspend,
+ .resume = b15_rac_resume,
+};
+#endif
+
static int __init b15_rac_init(void)
{
struct device_node *dn;
@@ -242,6 +286,10 @@ static int __init b15_rac_init(void)
goto out_cpu_dead;
#endif

+#ifdef CONFIG_PM_SLEEP
+ register_syscore_ops(&b15_rac_syscore_ops);
+#endif
+
spin_lock(&rac_lock);
reg = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
for_each_possible_cpu(cpu)
--
2.9.3