MIPS: Add generic CM probe & access code

The kernel currently only probes for a MIPS Coherence Manager in the
Malta interrupt code in order to detect & enable the GIC. However CM is
not Malta-specific, so this should really be more generic. This patch
introduces some non-Malta-specific code which probes for a CM and
performs some basic initialisation.

A new header, with temporarily duplicated register definitions, is
introduced in order to:

  1) Allow the new definitions to be correct with regards to the
     CM documentation, as many of those in gcmpregs.h aren't.

  2) Allow switching away from the REG() macro used via a few layers of
     nested macros in order to access registers in gcmpregs.h. This
     patch instead introduced accessor functions akin to the
     {read,write}_c0_* functions used for cop0 registers.

  3) Allow users of the CM to be migrated one by one.

  4) Switch from the name 'GCMP' to 'CM' since the Coherence Manager is
     what this code is actually dealing with.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6360/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -2006,6 +2006,9 @@ config MIPS_CMP
 config MIPS_GIC_IPI
 	bool
 
+config MIPS_CM
+	bool
+
 config SB1_PASS_1_WORKAROUNDS
 	bool
 	depends on CPU_SB1_PASS_1

arch/mips/kernel/Makefile

@@ -103,6 +103,8 @@ obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event_mipsxx.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 
+obj-$(CONFIG_MIPS_CM)		+= mips-cm.o
+
 #
 # DSP ASE supported for MIPS32 or MIPS64 Release 2 cores only. It is not
 # safe to unconditionnaly use the assembler -mdsp / -mdspr2 switches

arch/mips/kernel/mips-cm.c

+/*
+ * Copyright (C) 2013 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/errno.h>
+
+#include <asm/mips-cm.h>
+#include <asm/mipsregs.h>
+
+void __iomem *mips_cm_base;
+void __iomem *mips_cm_l2sync_base;
+
+phys_t __mips_cm_phys_base(void)
+{
+	u32 config3 = read_c0_config3();
+	u32 cmgcr;
+
+	/* Check the CMGCRBase register is implemented */
+	if (!(config3 & MIPS_CONF3_CMGCR))
+		return 0;
+
+	/* Read the address from CMGCRBase */
+	cmgcr = read_c0_cmgcrbase();
+	return (cmgcr & MIPS_CMGCRF_BASE) << (36 - 32);
+}
+
+phys_t mips_cm_phys_base(void)
+	__attribute__((weak, alias("__mips_cm_phys_base")));
+
+phys_t __mips_cm_l2sync_phys_base(void)
+{
+	u32 base_reg;
+
+	/*
+	 * If the L2-only sync region is already enabled then leave it at it's
+	 * current location.
+	 */
+	base_reg = read_gcr_l2_only_sync_base();
+	if (base_reg & CM_GCR_L2_ONLY_SYNC_BASE_SYNCEN_MSK)
+		return base_reg & CM_GCR_L2_ONLY_SYNC_BASE_SYNCBASE_MSK;
+
+	/* Default to following the CM */
+	return mips_cm_phys_base() + MIPS_CM_GCR_SIZE;
+}
+
+phys_t mips_cm_l2sync_phys_base(void)
+	__attribute__((weak, alias("__mips_cm_l2sync_phys_base")));
+
+static void mips_cm_probe_l2sync(void)
+{
+	unsigned major_rev;
+	phys_t addr;
+
+	/* L2-only sync was introduced with CM major revision 6 */
+	major_rev = (read_gcr_rev() & CM_GCR_REV_MAJOR_MSK) >>
+		CM_GCR_REV_MAJOR_SHF;
+	if (major_rev < 6)
+		return;
+
+	/* Find a location for the L2 sync region */
+	addr = mips_cm_l2sync_phys_base();
+	BUG_ON((addr & CM_GCR_L2_ONLY_SYNC_BASE_SYNCBASE_MSK) != addr);
+	if (!addr)
+		return;
+
+	/* Set the region base address & enable it */
+	write_gcr_l2_only_sync_base(addr | CM_GCR_L2_ONLY_SYNC_BASE_SYNCEN_MSK);
+
+	/* Map the region */
+	mips_cm_l2sync_base = ioremap_nocache(addr, MIPS_CM_L2SYNC_SIZE);
+}
+
+int mips_cm_probe(void)
+{
+	phys_t addr;
+	u32 base_reg;
+
+	addr = mips_cm_phys_base();
+	BUG_ON((addr & CM_GCR_BASE_GCRBASE_MSK) != addr);
+	if (!addr)
+		return -ENODEV;
+
+	mips_cm_base = ioremap_nocache(addr, MIPS_CM_GCR_SIZE);
+	if (!mips_cm_base)
+		return -ENXIO;
+
+	/* sanity check that we're looking at a CM */
+	base_reg = read_gcr_base();
+	if ((base_reg & CM_GCR_BASE_GCRBASE_MSK) != addr) {
+		pr_err("GCRs appear to have been moved (expected them at 0x%08lx)!\n",
+		       (unsigned long)addr);
+		mips_cm_base = NULL;
+		return -ENODEV;
+	}
+
+	/* set default target to memory */
+	base_reg &= ~CM_GCR_BASE_CMDEFTGT_MSK;
+	base_reg |= CM_GCR_BASE_CMDEFTGT_MEM;
+	write_gcr_base(base_reg);
+
+	/* disable CM regions */
+	write_gcr_reg0_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
+	write_gcr_reg0_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
+	write_gcr_reg1_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
+	write_gcr_reg1_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
+	write_gcr_reg2_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
+	write_gcr_reg2_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
+	write_gcr_reg3_base(CM_GCR_REGn_BASE_BASEADDR_MSK);
+	write_gcr_reg3_mask(CM_GCR_REGn_MASK_ADDRMASK_MSK);
+
+	/* probe for an L2-only sync region */
+	mips_cm_probe_l2sync();
+
+	return 0;
+}