[XEN v6 04/12] xen/arm: smmu: Use writeq_relaxed_non_atomic() for writing to SMMU_CBn_TTBR0

[Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>]

Refer ARM IHI 0062D.c ID070116 (SMMU 2.0 spec), 17-360, 17.3.9,
SMMU_CBn_TTBR0 is a 64 bit register. Thus, one can use
writeq_relaxed_non_atomic() to write to it instead of invoking
writel_relaxed() twice for lower half and upper half of the register.

This also helps us as p2maddr is 'paddr_t' (which may be u32 in future).
Thus, one can assign p2maddr to a 64 bit register and do the bit
manipulations on it, to generate the value for SMMU_CBn_TTBR0.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
Changes from -

v1 - 1. Extracted the patch from "[XEN v1 8/9] xen/arm: Other adaptations 
required to support 32bit paddr".
Use writeq_relaxed_non_atomic() to write u64 register in a non-atomic
fashion.

v2 - 1. Added R-b.

v3 - 1. No changes.

v4 - 1. Reordered the R-b. No further changes.
(This patch can be committed independent of the series).

v5 - Used 'uint64_t' instead of u64. As the change looked trivial to me, I
retained the R-b.

 xen/drivers/passthrough/arm/smmu.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/xen/drivers/passthrough/arm/smmu.c 
b/xen/drivers/passthrough/arm/smmu.c
index 79281075ba..fb8bef5f69 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -499,8 +499,7 @@ enum arm_smmu_s2cr_privcfg {
 #define ARM_SMMU_CB_SCTLR              0x0
 #define ARM_SMMU_CB_RESUME             0x8
 #define ARM_SMMU_CB_TTBCR2             0x10
-#define ARM_SMMU_CB_TTBR0_LO           0x20
-#define ARM_SMMU_CB_TTBR0_HI           0x24
+#define ARM_SMMU_CB_TTBR0              0x20
 #define ARM_SMMU_CB_TTBCR              0x30
 #define ARM_SMMU_CB_S1_MAIR0           0x38
 #define ARM_SMMU_CB_FSR                        0x58
@@ -1083,6 +1082,7 @@ static void arm_smmu_flush_pgtable(struct arm_smmu_device 
*smmu, void *addr,
 static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain)
 {
        u32 reg;
+       uint64_t reg64;
        bool stage1;
        struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
        struct arm_smmu_device *smmu = smmu_domain->smmu;
@@ -1177,12 +1177,13 @@ static void arm_smmu_init_context_bank(struct 
arm_smmu_domain *smmu_domain)
        dev_notice(smmu->dev, "d%u: p2maddr 0x%"PRIpaddr"\n",
                   smmu_domain->cfg.domain->domain_id, p2maddr);
 
-       reg = (p2maddr & ((1ULL << 32) - 1));
-       writel_relaxed(reg, cb_base + ARM_SMMU_CB_TTBR0_LO);
-       reg = (p2maddr >> 32);
+       reg64 = p2maddr;
+
        if (stage1)
-               reg |= ARM_SMMU_CB_ASID(cfg) << TTBRn_HI_ASID_SHIFT;
-       writel_relaxed(reg, cb_base + ARM_SMMU_CB_TTBR0_HI);
+               reg64 |= (((uint64_t) (ARM_SMMU_CB_ASID(cfg) << 
TTBRn_HI_ASID_SHIFT))
+                        << 32);
+
+       writeq_relaxed_non_atomic(reg64, cb_base + ARM_SMMU_CB_TTBR0);
 
        /*
         * TTBCR
-- 
2.17.1