MIPS: smp-cps: Don't rely on CP0_CMGCRBASE

CP0_CMGCRBASE is not always available on CPS enabled system
such as early proAptiv.

For early SMP bring up where we can't safely access memeory,
we patch the entry of CPS NMI vector to inject CMGCR address
directly into register during early core bringup.

For VPE bringup as the core is already coherenct at that point
we just read the variable to obtain the address.

Signed-off-by: Jiaxun Yang <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>

Author: FlyGoat

arch/mips/include/asm/smp-cps.h

@@ -7,6 +7,8 @@
 #ifndef __MIPS_ASM_SMP_CPS_H__
 #define __MIPS_ASM_SMP_CPS_H__
 
+#define CPS_ENTRY_PATCH_INSNS	6
+
 #ifndef __ASSEMBLY__
 
 struct vpe_boot_config {
@@ -30,6 +32,8 @@ extern void mips_cps_boot_vpes(struct core_boot_config *cfg, unsigned vpe);
 extern void mips_cps_pm_save(void);
 extern void mips_cps_pm_restore(void);
 
+extern void *mips_cps_core_entry_patch_end;
+
 #ifdef CONFIG_MIPS_CPS
 
 extern bool mips_cps_smp_in_use(void);

arch/mips/kernel/cps-vec.S

@@ -13,6 +13,7 @@
 #include <asm/mipsregs.h>
 #include <asm/mipsmtregs.h>
 #include <asm/pm.h>
+#include <asm/smp-cps.h>
 
 #define GCR_CPC_BASE_OFS	0x0088
 #define GCR_CL_COHERENCE_OFS	0x2008
@@ -80,25 +81,20 @@
 	 nop
 	.endm
 
-	/* Calculate an uncached address for the CM GCRs */
-	.macro	cmgcrb	dest
-	.set	push
-	.set	noat
-	MFC0	$1, CP0_CMGCRBASE
-	PTR_SLL	$1, $1, 4
-	PTR_LI	\dest, UNCAC_BASE
-	PTR_ADDU \dest, \dest, $1
-	.set	pop
-	.endm
 
 .balign 0x1000
 
 LEAF(mips_cps_core_entry)
 	/*
-	 * These first 4 bytes will be patched by cps_smp_setup to load the
-	 * CCA to use into register s0.
+	 * These first several instructions will be patched by cps_smp_setup to load the
+	 * CCA to use into register s0 and GCR base address to register s1.
 	 */
-	.word	0
+	.rept   CPS_ENTRY_PATCH_INSNS
+	nop
+	.endr
+
+	.global mips_cps_core_entry_patch_end
+mips_cps_core_entry_patch_end:
 
 	/* Check whether we're here due to an NMI */
 	mfc0	k0, CP0_STATUS
@@ -121,8 +117,7 @@ not_nmi:
 	mtc0	t0, CP0_STATUS
 
 	/* Skip cache & coherence setup if we're already coherent */
-	cmgcrb	v1
-	lw	s7, GCR_CL_COHERENCE_OFS(v1)
+	lw	s7, GCR_CL_COHERENCE_OFS(s1)
 	bnez	s7, 1f
 	 nop
 
@@ -132,7 +127,7 @@ not_nmi:
 
 	/* Enter the coherent domain */
 	li	t0, 0xff
-	sw	t0, GCR_CL_COHERENCE_OFS(v1)
+	sw	t0, GCR_CL_COHERENCE_OFS(s1)
 	ehb
 
 	/* Set Kseg0 CCA to that in s0 */
@@ -305,8 +300,7 @@ LEAF(mips_cps_core_init)
  */
 LEAF(mips_cps_get_bootcfg)
 	/* Calculate a pointer to this cores struct core_boot_config */
-	cmgcrb	t0
-	lw	t0, GCR_CL_ID_OFS(t0)
+	lw	t0, GCR_CL_ID_OFS(s1)
 	li	t1, COREBOOTCFG_SIZE
 	mul	t0, t0, t1
 	PTR_LA	t1, mips_cps_core_bootcfg
@@ -366,8 +360,9 @@ LEAF(mips_cps_boot_vpes)
 	has_vp	t0, 5f
 
 	/* Find base address of CPC */
-	cmgcrb	t3
-	PTR_L	t1, GCR_CPC_BASE_OFS(t3)
+	PTR_LA	t1, mips_gcr_base
+	PTR_L	t1, 0(t1)
+	PTR_L	t1, GCR_CPC_BASE_OFS(t1)
 	PTR_LI	t2, ~0x7fff
 	and	t1, t1, t2
 	PTR_LI	t2, UNCAC_BASE

arch/mips/kernel/smp-cps.c

@@ -162,6 +162,8 @@ static void __init cps_prepare_cpus(unsigned int max_cpus)
 	 */
 	entry_code = (u32 *)&mips_cps_core_entry;
 	uasm_i_addiu(&entry_code, 16, 0, cca);
+	UASM_i_LA(&entry_code, 17, (long)mips_gcr_base);
+	BUG_ON((void *)entry_code > (void *)&mips_cps_core_entry_patch_end);
 	blast_dcache_range((unsigned long)&mips_cps_core_entry,
 			   (unsigned long)entry_code);
 	bc_wback_inv((unsigned long)&mips_cps_core_entry,