[PATCH] powerpc/6xx: set High BAT Enable flag on G2 cores

Matthias Schiffer
2023-12-21T12:46:32Z

MMU_FTR_USE_HIGH_BATS is set for G2-based cores (G2_LE, e300cX), but the
high BATs need to be enabled in HID2 to work. Add register definitions
and introduce a G2 variant of __setup_cpu_603.

This fixes boot on CPUs like the MPC5200B with STRICT_KERNEL_RWX enabled.

Fixes: e4d6654ebe6e ("powerpc/mm/32s: rework mmu_mapin_ram()")
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
---
arch/powerpc/include/asm/cpu_setup.h | 1 +
arch/powerpc/include/asm/reg.h | 2 ++
arch/powerpc/kernel/cpu_setup_6xx.S | 25 ++++++++++++++++++++++-
arch/powerpc/kernel/cpu_specs_book3s_32.h | 10 ++++-----
4 files changed, 32 insertions(+), 6 deletions(-)

I have only tested this on the MPC5200B (G2_LE), but according to the
e300 manual, e300cX cores should behave the same.

The Fixes tag is the best I could come up with - I believe that the
underlying issue of setting USE_HIGH_BATS without actually enabling them
is as old as Linux's PowerPC implementation, but the specific code
causing the boot failure was added in the mentioned commit.

Another issue I found in the code is that
arch/powerpc/platforms/52xx/lite5200_sleep.S uses the SPRN_HID2 definition
which does not refer to HID2 on the 5200... but that will be for someone
else to fix, if there is still anyone left using that platform.

diff --git a/arch/powerpc/include/asm/cpu_setup.h b/arch/powerpc/include/asm/cpu_setup.h
index 30e2fe3895024..68d804e74d221 100644
--- a/arch/powerpc/include/asm/cpu_setup.h
+++ b/arch/powerpc/include/asm/cpu_setup.h
@@ -35,6 +35,7 @@ void __setup_cpu_750fx(unsigned long offset, struct cpu_spec *spec);
void __setup_cpu_7400(unsigned long offset, struct cpu_spec *spec);
void __setup_cpu_7410(unsigned long offset, struct cpu_spec *spec);
void __setup_cpu_745x(unsigned long offset, struct cpu_spec *spec);
+void __setup_cpu_g2(unsigned long offset, struct cpu_spec *spec);

void __setup_cpu_ppc970(unsigned long offset, struct cpu_spec *spec);
void __setup_cpu_ppc970MP(unsigned long offset, struct cpu_spec *spec);
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 4ae4ab9090a2d..f5641fcd1da85 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -617,6 +617,8 @@
#endif
#define SPRN_HID2 0x3F8 /* Hardware Implementation Register 2 */
#define SPRN_HID2_GEKKO 0x398 /* Gekko HID2 Register */
+#define SPRN_HID2_G2 0x3F3 /* G2 HID2 Register */
+#define HID2_HBE_G2 (1<<18) /* High BAT Enable (G2) */
#define SPRN_IABR 0x3F2 /* Instruction Address Breakpoint Register */
#define SPRN_IABR2 0x3FA /* 83xx */
#define SPRN_IBCR 0x135 /* 83xx Insn Breakpoint Control Reg */
diff --git a/arch/powerpc/kernel/cpu_setup_6xx.S b/arch/powerpc/kernel/cpu_setup_6xx.S
index f29ce3dd6140f..c67d32e04df9c 100644
--- a/arch/powerpc/kernel/cpu_setup_6xx.S
+++ b/arch/powerpc/kernel/cpu_setup_6xx.S
@@ -81,6 +81,20 @@ _GLOBAL(__setup_cpu_745x)
bl setup_745x_specifics
mtlr r5
blr
+_GLOBAL(__setup_cpu_g2)
+ mflr r5
+BEGIN_MMU_FTR_SECTION
+ li r10,0
+ mtspr SPRN_SPRG_603_LRU,r10 /* init SW LRU tracking */
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
+
+BEGIN_FTR_SECTION
+ bl __init_fpu_registers
+END_FTR_SECTION_IFCLR(CPU_FTR_FPU_UNAVAILABLE)
+ bl setup_common_caches
+ bl setup_g2_hid2
+ mtlr r5
+ blr

/* Enable caches for 603's, 604, 750 & 7400 */
SYM_FUNC_START_LOCAL(setup_common_caches)
@@ -115,6 +129,16 @@ SYM_FUNC_START_LOCAL(setup_604_hid0)
blr
SYM_FUNC_END(setup_604_hid0)

+/* Enable high BATs for G2 (G2_LE, e300cX) */
+SYM_FUNC_START_LOCAL(setup_g2_hid2)
+ mfspr r11,SPRN_HID2_G2
+ oris r11,r11,HID2_HBE_G2@h
+ mtspr SPRN_HID2_G2,r11
+ sync
+ isync
+ blr
+SYM_FUNC_END(setup_g2_hid2)
+
/* 7400 <= rev 2.7 and 7410 rev = 1.0 suffer from some
* erratas we work around here.
* Moto MPC710CE.pdf describes them, those are errata
@@ -495,4 +519,3 @@ _GLOBAL(__restore_cpu_setup)
mtcr r7
blr
_ASM_NOKPROBE_SYMBOL(__restore_cpu_setup)
-
diff --git a/arch/powerpc/kernel/cpu_specs_book3s_32.h b/arch/powerpc/kernel/cpu_specs_book3s_32.h
index 3714634d194a1..83f054fcf837c 100644
--- a/arch/powerpc/kernel/cpu_specs_book3s_32.h
+++ b/arch/powerpc/kernel/cpu_specs_book3s_32.h
@@ -69,7 +69,7 @@ static struct cpu_spec cpu_specs[] __initdata = {
.mmu_features = MMU_FTR_USE_HIGH_BATS,
.icache_bsize = 32,
.dcache_bsize = 32,
- .cpu_setup = __setup_cpu_603,
+ .cpu_setup = __setup_cpu_g2,
.machine_check = machine_check_generic,
.platform = "ppc603",
},
@@ -83,7 +83,7 @@ static struct cpu_spec cpu_specs[] __initdata = {
.mmu_features = MMU_FTR_USE_HIGH_BATS,
.icache_bsize = 32,
.dcache_bsize = 32,
- .cpu_setup = __setup_cpu_603,
+ .cpu_setup = __setup_cpu_g2,
.machine_check = machine_check_83xx,
.platform = "ppc603",
},
@@ -96,7 +96,7 @@ static struct cpu_spec cpu_specs[] __initdata = {
.mmu_features = MMU_FTR_USE_HIGH_BATS | MMU_FTR_NEED_DTLB_SW_LRU,
.icache_bsize = 32,
.dcache_bsize = 32,
- .cpu_setup = __setup_cpu_603,
+ .cpu_setup = __setup_cpu_g2,
.machine_check = machine_check_83xx,
.platform = "ppc603",
},
@@ -109,7 +109,7 @@ static struct cpu_spec cpu_specs[] __initdata = {
.mmu_features = MMU_FTR_USE_HIGH_BATS | MMU_FTR_NEED_DTLB_SW_LRU,
.icache_bsize = 32,
.dcache_bsize = 32,
- .cpu_setup = __setup_cpu_603,
+ .cpu_setup = __setup_cpu_g2,
.machine_check = machine_check_83xx,
.num_pmcs = 4,
.platform = "ppc603",
@@ -123,7 +123,7 @@ static struct cpu_spec cpu_specs[] __initdata = {
.mmu_features = MMU_FTR_USE_HIGH_BATS | MMU_FTR_NEED_DTLB_SW_LRU,
.icache_bsize = 32,
.dcache_bsize = 32,
- .cpu_setup = __setup_cpu_603,
+ .cpu_setup = __setup_cpu_g2,
.machine_check = machine_check_83xx,
.num_pmcs = 4,
.platform = "ppc603",