arm64: setup: name `tcr` register

In __cpu_setup we conditionally manipulate the TCR_EL1 value in x10
after previously using x10 as a scratch register for unrelated temporary
variables.

To make this a bit clearer, let's move the TCR_EL1 value into a named
register `tcr`. To simplify the register allocation, this is placed in
the highest available caller-saved scratch register, tcr.

Following the example of `mair`, we initialise the register with the
default value prior to any feature discovery, and write it to MAIR_EL1
after all feature discovery is complete, which allows us to simplify the
featuere discovery code.

The existing `mte_tcr` register is no longer needed, and is replaced by
the use of x10 as a temporary, matching the rest of the MTE feature
discovery assembly in __cpu_setup. As x20 is no longer used, the
function is now AAPCS compliant, as we've generally aimed for in our
assembly functions.

There should be no functional change as as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210326180137.43119-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index f560b6f..0a48191 100644 (file)
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -419,15 +419,17 @@ SYM_FUNC_START(__cpu_setup)
        reset_amuserenr_el0 x1                  // Disable AMU access from EL0
 
        /*
-        * Memory region attributes
+        * Default values for VMSA control registers. These will be adjusted
+        * below depending on detected CPU features.
         */
        mair    .req    x17
+       tcr     .req    x16
        mov_q   mair, MAIR_EL1_SET
-#ifdef CONFIG_ARM64_MTE
-       mte_tcr .req    x20
-
-       mov     mte_tcr, #0
+       mov_q   tcr, TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
+                       TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
+                       TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS
 
+#ifdef CONFIG_ARM64_MTE
        /*
         * Update MAIR_EL1, GCR_EL1 and TFSR*_EL1 if MTE is supported
         * (ID_AA64PFR1_EL1[11:8] > 1).
@@ -450,36 +452,26 @@ SYM_FUNC_START(__cpu_setup)
        msr_s   SYS_TFSRE0_EL1, xzr
 
        /* set the TCR_EL1 bits */
-       mov_q   mte_tcr, TCR_KASAN_HW_FLAGS
+       mov_q   x10, TCR_KASAN_HW_FLAGS
+       orr     tcr, tcr, x10
 1:
 #endif
-       /*
-        * Set/prepare TCR and TTBR. TCR_EL1.T1SZ gets further
-        * adjusted if the kernel is compiled with 52bit VA support.
-        */
-       mov_q   x10, TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
-                       TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
-                       TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS
-#ifdef CONFIG_ARM64_MTE
-       orr     x10, x10, mte_tcr
-       .unreq  mte_tcr
-#endif
-       tcr_clear_errata_bits x10, x9, x5
+       tcr_clear_errata_bits tcr, x9, x5
 
 #ifdef CONFIG_ARM64_VA_BITS_52
        ldr_l           x9, vabits_actual
        sub             x9, xzr, x9
        add             x9, x9, #64
-       tcr_set_t1sz    x10, x9
+       tcr_set_t1sz    tcr, x9
 #else
        ldr_l           x9, idmap_t0sz
 #endif
-       tcr_set_t0sz    x10, x9
+       tcr_set_t0sz    tcr, x9
 
        /*
         * Set the IPS bits in TCR_EL1.
         */
-       tcr_compute_pa_size x10, #TCR_IPS_SHIFT, x5, x6
+       tcr_compute_pa_size tcr, #TCR_IPS_SHIFT, x5, x6
 #ifdef CONFIG_ARM64_HW_AFDBM
        /*
         * Enable hardware update of the Access Flags bit.
@@ -489,11 +481,11 @@ SYM_FUNC_START(__cpu_setup)
        mrs     x9, ID_AA64MMFR1_EL1
        and     x9, x9, #0xf
        cbz     x9, 1f
-       orr     x10, x10, #TCR_HA               // hardware Access flag update
+       orr     tcr, tcr, #TCR_HA               // hardware Access flag update
 1:
 #endif /* CONFIG_ARM64_HW_AFDBM */
        msr     mair_el1, mair
-       msr     tcr_el1, x10
+       msr     tcr_el1, tcr
        /*
         * Prepare SCTLR
         */
@@ -501,4 +493,5 @@ SYM_FUNC_START(__cpu_setup)
        ret                                     // return to head.S
 
        .unreq  mair
+       .unreq  tcr
 SYM_FUNC_END(__cpu_setup)