MIPS: Allow using more than 32-bit addresses for reset vectors when possible

While most MIPS64 CPUs use 32-bit values for their VP Local Reset
Exception Base registers, some I6500 CPUs can utilize a 64-bit value,
allowing addressing up to 47 bits of physical memory.

For the EyeQ6H CPU, where physical memory addresses exceed the 4GB
limit, utilizing this feature is mandatory to enable SMP support.

Unfortunately, there is no way to detect this capability based solely
on the ID of the CPU. According to Imagination, which designed the
CPU, the only reliable method is to fill the reset base field with
0xFF and then read back its value. If the upper part of the read-back
value is zero, it indicates that the address space is limited to 32
bits.

Signed-off-by: Gregory CLEMENT <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>

Author: gclement

arch/mips/include/asm/mips-cm.h

@@ -326,7 +326,9 @@ GCR_CX_ACCESSOR_RW(32, 0x018, other)
 
 /* GCR_Cx_RESET_BASE - Configure where powered up cores will fetch from */
 GCR_CX_ACCESSOR_RW(32, 0x020, reset_base)
+GCR_CX_ACCESSOR_RW(64, 0x020, reset64_base)
 #define CM_GCR_Cx_RESET_BASE_BEVEXCBASE		GENMASK(31, 12)
+#define CM_GCR_Cx_RESET64_BASE_BEVEXCBASE	GENMASK_ULL(47, 12)
 #define CM_GCR_Cx_RESET_BASE_MODE		BIT(1)
 
 /* GCR_Cx_ID - Identify the current core */

arch/mips/kernel/smp-cps.c

@@ -37,7 +37,7 @@ enum label_id {
 UASM_L_LA(_not_nmi)
 
 static DECLARE_BITMAP(core_power, NR_CPUS);
-static uint32_t core_entry_reg;
+static u64 core_entry_reg;
 static phys_addr_t cps_vec_pa;
 
 struct core_boot_config *mips_cps_core_bootcfg;
@@ -94,6 +94,20 @@ static void __init *mips_cps_build_core_entry(void *addr)
 	return p;
 }
 
+static bool __init check_64bit_reset(void)
+{
+	bool cx_64bit_reset = false;
+
+	mips_cm_lock_other(0, 0, 0, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
+	write_gcr_co_reset64_base(CM_GCR_Cx_RESET64_BASE_BEVEXCBASE);
+	if ((read_gcr_co_reset64_base() & CM_GCR_Cx_RESET64_BASE_BEVEXCBASE) ==
+	    CM_GCR_Cx_RESET64_BASE_BEVEXCBASE)
+		cx_64bit_reset = true;
+	mips_cm_unlock_other();
+
+	return cx_64bit_reset;
+}
+
 static int __init allocate_cps_vecs(void)
 {
 	/* Try to allocate in KSEG1 first */
@@ -105,11 +119,23 @@ static int __init allocate_cps_vecs(void)
 					CM_GCR_Cx_RESET_BASE_BEVEXCBASE;
 
 	if (!cps_vec_pa && mips_cm_is64) {
-		cps_vec_pa = memblock_phys_alloc_range(BEV_VEC_SIZE, BEV_VEC_ALIGN,
-							0x0, SZ_4G - 1);
-		if (cps_vec_pa)
-			core_entry_reg = (cps_vec_pa & CM_GCR_Cx_RESET_BASE_BEVEXCBASE) |
+		phys_addr_t end;
+
+		if (check_64bit_reset()) {
+			pr_info("VP Local Reset Exception Base support 47 bits address\n");
+			end = MEMBLOCK_ALLOC_ANYWHERE;
+		} else {
+			end = SZ_4G - 1;
+		}
+		cps_vec_pa = memblock_phys_alloc_range(BEV_VEC_SIZE, BEV_VEC_ALIGN, 0, end);
+		if (cps_vec_pa) {
+			if (check_64bit_reset())
+				core_entry_reg = (cps_vec_pa & CM_GCR_Cx_RESET64_BASE_BEVEXCBASE) |
+					CM_GCR_Cx_RESET_BASE_MODE;
+			else
+				core_entry_reg = (cps_vec_pa & CM_GCR_Cx_RESET_BASE_BEVEXCBASE) |
 					CM_GCR_Cx_RESET_BASE_MODE;
+		}
 	}
 
 	if (!cps_vec_pa)
@@ -308,7 +334,10 @@ static void boot_core(unsigned int core, unsigned int vpe_id)
 	mips_cm_lock_other(0, core, 0, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
 
 	/* Set its reset vector */
-	write_gcr_co_reset_base(core_entry_reg);
+	if (mips_cm_is64)
+		write_gcr_co_reset64_base(core_entry_reg);
+	else
+		write_gcr_co_reset_base(core_entry_reg);
 
 	/* Ensure its coherency is disabled */
 	write_gcr_co_coherence(0);
@@ -411,7 +440,10 @@ static int cps_boot_secondary(int cpu, struct task_struct *idle)
 
 	if (cpu_has_vp) {
 		mips_cm_lock_other(0, core, vpe_id, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
-		write_gcr_co_reset_base(core_entry_reg);
+		if (mips_cm_is64)
+			write_gcr_co_reset64_base(core_entry_reg);
+		else
+			write_gcr_co_reset_base(core_entry_reg);
 		mips_cm_unlock_other();
 	}