linux-kernel - [PATCH 08/10] MIPS: CM: introduce core-other locking functions

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Date:	Tue, 22 Sep 2015 11:12:16 -0700
From:	Paul Burton <paul.burton@...tec.com>
To:	<linux-mips@...ux-mips.org>
CC:	Paul Burton <paul.burton@...tec.com>,
	<linux-kernel@...r.kernel.org>,
	James Hogan <james.hogan@...tec.com>,
	Markos Chandras <markos.chandras@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 08/10] MIPS: CM: introduce core-other locking functions

Introduce mips_cm_lock_other & mips_cm_unlock_other, mirroring the
existing CPC equivalents, in order to lock access from the current core
to another via the core-other GCR region. This hasn't been required in
the past but with CM3 the CPC starts using GCR_CL_OTHER rather than
CPC_CL_OTHER and this will be required for safety.

Signed-off-by: Paul Burton <paul.burton@...tec.com>
---

 arch/mips/include/asm/mips-cm.h | 32 ++++++++++++++++++++++++++++++++
 arch/mips/kernel/mips-cm.c      | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
index 2796424..29e6b9d 100644
--- a/arch/mips/include/asm/mips-cm.h
+++ b/arch/mips/include/asm/mips-cm.h
@@ -329,6 +329,10 @@ BUILD_CM_Cx_R_(tcid_8_priority,	0x80)
 /* GCR_Cx_OTHER register fields */
 #define CM_GCR_Cx_OTHER_CORENUM_SHF		16
 #define CM_GCR_Cx_OTHER_CORENUM_MSK		(_ULCAST_(0xffff) << 16)
+#define CM3_GCR_Cx_OTHER_CORE_SHF		8
+#define CM3_GCR_Cx_OTHER_CORE_MSK		(_ULCAST_(0x3f) << 8)
+#define CM3_GCR_Cx_OTHER_VP_SHF			0
+#define CM3_GCR_Cx_OTHER_VP_MSK			(_ULCAST_(0x7) << 0)
 
 /* GCR_Cx_RESET_BASE register fields */
 #define CM_GCR_Cx_RESET_BASE_BEVEXCBASE_SHF	12
@@ -405,4 +409,32 @@ static inline int mips_cm_revision(void)
 	return read_gcr_rev();
 }
 
+#ifdef CONFIG_MIPS_CM
+
+/**
+ * mips_cm_lock_other - lock access to another core
+ * @core: the other core to be accessed
+ * @vp: the VP within the other core to be accessed
+ *
+ * Call before operating upon a core via the 'other' register region in
+ * order to prevent the region being moved during access. Must be followed
+ * by a call to mips_cm_unlock_other.
+ */
+extern void mips_cm_lock_other(unsigned int core, unsigned int vp);
+
+/**
+ * mips_cm_unlock_other - unlock access to another core
+ *
+ * Call after operating upon another core via the 'other' register region.
+ * Must be called after mips_cm_lock_other.
+ */
+extern void mips_cm_unlock_other(void);
+
+#else /* !CONFIG_MIPS_CM */
+
+static inline void mips_cm_lock_other(unsigned int core) { }
+static inline void mips_cm_unlock_other(void) { }
+
+#endif /* !CONFIG_MIPS_CM */
+
 #endif /* __MIPS_ASM_MIPS_CM_H__ */
diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
index b8ceee5..fef2647 100644
--- a/arch/mips/kernel/mips-cm.c
+++ b/arch/mips/kernel/mips-cm.c
@@ -9,6 +9,8 @@
  */
 
 #include <linux/errno.h>
+#include <linux/percpu.h>
+#include <linux/spinlock.h>
 
 #include <asm/mips-cm.h>
 #include <asm/mipsregs.h>
@@ -136,6 +138,9 @@ static char *cm3_causes[32] = {
 	"0x19", "0x1a", "0x1b", "0x1c", "0x1d", "0x1e", "0x1f"
 };
 
+static DEFINE_PER_CPU_ALIGNED(spinlock_t, cm_core_lock);
+static DEFINE_PER_CPU_ALIGNED(unsigned long, cm_core_lock_flags);
+
 phys_addr_t __mips_cm_phys_base(void)
 {
 	u32 config3 = read_c0_config3();
@@ -200,6 +205,7 @@ int mips_cm_probe(void)
 {
 	phys_addr_t addr;
 	u32 base_reg;
+	unsigned cpu;
 
 	/*
 	 * No need to probe again if we have already been
@@ -247,9 +253,42 @@ int mips_cm_probe(void)
 	/* determine register width for this CM */
 	mips_cm_is64 = config_enabled(CONFIG_64BIT) && (mips_cm_revision() >= CM_REV_CM3);
 
+	for_each_possible_cpu(cpu)
+		spin_lock_init(&per_cpu(cm_core_lock, cpu));
+
 	return 0;
 }
 
+void mips_cm_lock_other(unsigned int core, unsigned int vp)
+{
+	unsigned curr_core;
+	u32 val;
+
+	preempt_disable();
+	curr_core = current_cpu_data.core;
+	spin_lock_irqsave(&per_cpu(cm_core_lock, curr_core),
+			  per_cpu(cm_core_lock_flags, curr_core));
+
+	if (mips_cm_revision() >= CM_REV_CM3) {
+		val = core << CM3_GCR_Cx_OTHER_CORE_SHF;
+		val |= vp << CM3_GCR_Cx_OTHER_VP_SHF;
+	} else {
+		BUG_ON(vp != 0);
+		val = core << CM_GCR_Cx_OTHER_CORENUM_SHF;
+	}
+
+	write_gcr_cl_other(val);
+}
+
+void mips_cm_unlock_other(void)
+{
+	unsigned curr_core = current_cpu_data.core;
+
+	spin_unlock_irqrestore(&per_cpu(cm_core_lock, curr_core),
+			       per_cpu(cm_core_lock_flags, curr_core));
+	preempt_enable();
+}
+
 void mips_cm_error_report(void)
 {
 	unsigned long revision = mips_cm_revision();
-- 
2.5.3

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