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Re: [XEN v6 04/12] xen/arm: smmu: Use writeq_relaxed_non_atomic() for writing to SMMU_CBn_TTBR0
- To: Michal Orzel <michal.orzel@xxxxxxx>
- From: Rahul Singh <Rahul.Singh@xxxxxxx>
- Date: Thu, 4 May 2023 14:31:37 +0000
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- Cc: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, Xen developer discussion <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "Stabellini, Stefano" <stefano.stabellini@xxxxxxx>, Julien Grall <julien@xxxxxxx>, "Volodymyr_Babchuk@xxxxxxxx" <Volodymyr_Babchuk@xxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, "andrew.cooper3@xxxxxxxxxx" <andrew.cooper3@xxxxxxxxxx>, "george.dunlap@xxxxxxxxxx" <george.dunlap@xxxxxxxxxx>, "jbeulich@xxxxxxxx" <jbeulich@xxxxxxxx>, "wl@xxxxxxx" <wl@xxxxxxx>
- Delivery-date: Thu, 04 May 2023 14:32:00 +0000
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- Thread-topic: [XEN v6 04/12] xen/arm: smmu: Use writeq_relaxed_non_atomic() for writing to SMMU_CBn_TTBR0
Hi Ayan,
On 4 May 2023, at 8:37 am, Michal Orzel <michal.orzel@xxxxxxx> wrote:
On
28/04/2023 19:55, Ayan Kumar Halder wrote:
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);
I
think << should be aligned to the second '(' above.
Reviewed-by:
Michal Orzel <michal.orzel@xxxxxxx>
With the Michal comment fixed.
Regards,
Rahul
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