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.

[ralf@linux-mips.org: Fix merge conflict.]

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11207/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
index 7740c4f..6516e9d 100644 (file)
--- a/arch/mips/include/asm/mips-cm.h
+++ b/arch/mips/include/asm/mips-cm.h
@@ -364,6 +364,10 @@ 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
@@ -474,4 +478,32 @@ static inline unsigned int mips_cm_vp_id(unsigned int cpu)
        return (core * mips_cm_max_vp_width()) + vp;
 }
 
+#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 02f7d7a..01908db 100644 (file)
--- 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)
 {
        u64 cm_error, cm_addr, cm_other;