[PATCH v2] armv8: always use current exception level for TCR_ELx access

[Andre Przywara]

Currently get_tcr() takes an "el" parameter, to select the proper
version of the TCR_ELx system register.
This is problematic in case of the Apple M1, since it runs with
HCR_EL2.E2H fixed to 1, so TCR_EL2 is actually using the TCR_EL1 layout,
and we get the wrong version.

For U-Boot's purposes the only sensible choice here is the current
exception level, and indeed most callers treat it like that, so let's
remove that parameter and read the current EL inside the function.
This allows us to check for the E2H bit, and pretend it's EL1 in this
case.

There are two callers which don't care about the EL, and they pass 0,
which looks wrong, but is irrelevant in these two cases, since we don't
use the return value there. So the change cannot affect those two.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
Changelog v1 ... v2:
- Give bit 34 a name, and also use that in start.S

Mark, can you please test this? The A53s I have here for a quick test
are igorant of this patch ...

 arch/arm/cpu/armv8/cache_v8.c           | 28 +++++++++++++++++++++----
 arch/arm/cpu/armv8/fsl-layerscape/cpu.c |  4 ++--
 arch/arm/cpu/armv8/start.S              |  2 +-
 arch/arm/include/asm/armv8/mmu.h        |  4 +++-
 4 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
index 3de18c7675b..e4736e56436 100644
--- a/arch/arm/cpu/armv8/cache_v8.c
+++ b/arch/arm/cpu/armv8/cache_v8.c
@@ -39,8 +39,28 @@ DECLARE_GLOBAL_DATA_PTR;
  *    off:          FFF
  */
 
-u64 get_tcr(int el, u64 *pips, u64 *pva_bits)
+static int get_effective_el(void)
 {
+	int el = current_el();
+
+	if (el == 2) {
+		u64 hcr_el2;
+
+		/*
+		 * If we are using the EL2&0 translation regime, the TCR_EL2
+		 * looks like the EL1 version, even though we are in EL2.
+		 */
+		__asm__ ("mrs %0, HCR_EL2\n" : "=r" (hcr_el2));
+		if (hcr_el2 & BIT(HCR_EL2_E2H_BIT))
+			return 1;
+	}
+
+	return el;
+}
+
+u64 get_tcr(u64 *pips, u64 *pva_bits)
+{
+	int el = get_effective_el();
 	u64 max_addr = 0;
 	u64 ips, va_bits;
 	u64 tcr;
@@ -115,7 +135,7 @@ static u64 *find_pte(u64 addr, int level)
 
 	debug("addr=%llx level=%d\n", addr, level);
 
-	get_tcr(0, NULL, &va_bits);
+	get_tcr(NULL, &va_bits);
 	if (va_bits < 39)
 		start_level = 1;
 
@@ -343,7 +363,7 @@ __weak u64 get_page_table_size(void)
 	u64 va_bits;
 	int start_level = 0;
 
-	get_tcr(0, NULL, &va_bits);
+	get_tcr(NULL, &va_bits);
 	if (va_bits < 39)
 		start_level = 1;
 
@@ -415,7 +435,7 @@ __weak void mmu_setup(void)
 		setup_all_pgtables();
 
 	el = current_el();
-	set_ttbr_tcr_mair(el, gd->arch.tlb_addr, get_tcr(el, NULL, NULL),
+	set_ttbr_tcr_mair(el, gd->arch.tlb_addr, get_tcr(NULL, NULL),
 			  MEMORY_ATTRIBUTES);
 
 	/* enable the mmu */
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
index 253008a9c13..c989a43cbeb 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
@@ -454,7 +454,7 @@ static inline void early_mmu_setup(void)
 
 	/* point TTBR to the new table */
 	set_ttbr_tcr_mair(el, gd->arch.tlb_addr,
-			  get_tcr(el, NULL, NULL) &
+			  get_tcr(NULL, NULL) &
 			  ~(TCR_ORGN_MASK | TCR_IRGN_MASK),
 			  MEMORY_ATTRIBUTES);
 
@@ -609,7 +609,7 @@ static inline void final_mmu_setup(void)
 	invalidate_icache_all();
 
 	/* point TTBR to the new table */
-	set_ttbr_tcr_mair(el, gd->arch.tlb_addr, get_tcr(el, NULL, NULL),
+	set_ttbr_tcr_mair(el, gd->arch.tlb_addr, get_tcr(NULL, NULL),
 			  MEMORY_ATTRIBUTES);
 
 	set_sctlr(get_sctlr() | CR_M);
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index d328e8c08a1..28f0df13f0d 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -125,7 +125,7 @@ pie_fixup_done:
 	msr	cptr_el3, xzr			/* Enable FP/SIMD */
 	b	0f
 2:	mrs	x1, hcr_el2
-	tbnz	x1, #34, 1f			/* HCR_EL2.E2H */
+	tbnz	x1, #HCR_EL2_E2H_BIT, 1f	/* HCR_EL2.E2H */
 	orr	x1, x1, #HCR_EL2_AMO_EL2	/* Route SErrors to EL2 */
 	msr	hcr_el2, x1
 	set_vbar vbar_el2, x0
diff --git a/arch/arm/include/asm/armv8/mmu.h b/arch/arm/include/asm/armv8/mmu.h
index c36b2cf5a58..9f58cedb650 100644
--- a/arch/arm/include/asm/armv8/mmu.h
+++ b/arch/arm/include/asm/armv8/mmu.h
@@ -103,6 +103,8 @@
 #define TCR_EL2_RSVD		(1U << 31 | 1 << 23)
 #define TCR_EL3_RSVD		(1U << 31 | 1 << 23)
 
+#define HCR_EL2_E2H_BIT		34
+
 #ifndef __ASSEMBLY__
 static inline void set_ttbr_tcr_mair(int el, u64 table, u64 tcr, u64 attr)
 {
@@ -134,7 +136,7 @@ struct mm_region {
 
 extern struct mm_region *mem_map;
 void setup_pgtables(void);
-u64 get_tcr(int el, u64 *pips, u64 *pva_bits);
+u64 get_tcr(u64 *pips, u64 *pva_bits);
 #endif
 
 #endif /* _ASM_ARMV8_MMU_H_ */
-- 
2.35.3