[PATCH v5 7/8] iommu/arm-smmu: Get associated RMR info and install bypass SMR
Steven Price
steven.price at arm.com
Thu Jun 3 04:27:30 PDT 2021
On 03/06/2021 09:52, Jon Nettleton wrote:
> On Mon, May 24, 2021 at 1:04 PM Shameer Kolothum
> <shameerali.kolothum.thodi at huawei.com> wrote:
>>
>> From: Jon Nettleton <jon at solid-run.com>
>>
>> Check if there is any RMR info associated with the devices behind
>> the SMMU and if any, install bypass SMRs for them. This is to
>> keep any ongoing traffic associated with these devices alive
>> when we enable/reset SMMU during probe().
>>
>> Signed-off-by: Jon Nettleton <jon at solid-run.com>
>> Signed-off-by: Steven Price <steven.price at arm.com>
>> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
>> ---
>> drivers/iommu/arm/arm-smmu/arm-smmu.c | 65 +++++++++++++++++++++++++++
>> 1 file changed, 65 insertions(+)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> index 6f72c4d208ca..56db3d3238fc 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> @@ -2042,6 +2042,67 @@ err_reset_platform_ops: __maybe_unused;
>> return err;
>> }
>>
>> +static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device *smmu)
>> +{
>> + struct list_head rmr_list;
>> + struct iommu_resv_region *e;
>> + int i, cnt = 0;
>> + u32 smr;
>> + u32 reg;
>> +
>> + INIT_LIST_HEAD(&rmr_list);
>> + if (iommu_dma_get_rmrs(dev_fwnode(smmu->dev), &rmr_list))
>> + return;
>> +
>> + reg = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_sCR0);
>> +
>> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
>> + /*
>> + * SMMU is already enabled and disallowing bypass, so preserve
>> + * the existing SMRs
>> + */
>> + for (i = 0; i < smmu->num_mapping_groups; i++) {
>> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
>> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
>> + continue;
>> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
>> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
>> + smmu->smrs[i].valid = true;
>> + }
>> + }
>> +
>> + list_for_each_entry(e, &rmr_list, list) {
>> + u32 sid = e->fw_data.rmr.sid;
>> +
>> + i = arm_smmu_find_sme(smmu, sid, ~0);
>> + if (i < 0)
>> + continue;
>> + if (smmu->s2crs[i].count == 0) {
>> + smmu->smrs[i].id = sid;
>> + smmu->smrs[i].mask = ~0;
Looking at this code again, that mask looks wrong! According to the SMMU
spec MASK[i]==1 means ID[i] is ignored. I.e. this means completely
ignore the ID...
I'm not at all sure why they designed the hardware that way round.
>> + smmu->smrs[i].valid = true;
>> + }
>> + smmu->s2crs[i].count++;
>> + smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
>> + smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
>> + smmu->s2crs[i].cbndx = 0xff;
>> +
>> + cnt++;
>> + }
>> +
>> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
>> + /* Remove the valid bit for unused SMRs */
>> + for (i = 0; i < smmu->num_mapping_groups; i++) {
>> + if (smmu->s2crs[i].count == 0)
>> + smmu->smrs[i].valid = false;
>> + }
>> + }
>> +
>> + dev_notice(smmu->dev, "\tpreserved %d boot mapping%s\n", cnt,
>> + cnt == 1 ? "" : "s");
>> + iommu_dma_put_rmrs(dev_fwnode(smmu->dev), &rmr_list);
>> +}
>> +
>> static int arm_smmu_device_probe(struct platform_device *pdev)
>> {
>> struct resource *res;
>> @@ -2168,6 +2229,10 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>> }
>>
>> platform_set_drvdata(pdev, smmu);
>> +
>> + /* Check for RMRs and install bypass SMRs if any */
>> + arm_smmu_rmr_install_bypass_smr(smmu);
>> +
>> arm_smmu_device_reset(smmu);
>> arm_smmu_test_smr_masks(smmu);
>>
>> --
>> 2.17.1
>>
>
> Shameer and Robin
>
> I finally got around to updating edk2 and the HoneyComb IORT tables to
> reflect the new standards.
> Out of the box the new patchset was generating errors immediatly after
> the smmu bringup.
>
> arm-smmu arm-smmu.0.auto: Unhandled context fault: fsr=0x402, iova=0x2080000140,
> fsynr=0x1d0040, cbfrsynra=0x4000, cb=0
>
> These errors were generated even with disable_bypass=0
>
> I tracked down the issue to
>
> This code is skipped as Robin said would be correct
If you're skipping the first bit of code, then that (hopefully) means
that the SMMU is disabled...
>> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
>> + /*
>> + * SMMU is already enabled and disallowing bypass, so preserve
>> + * the existing SMRs
>> + */
>> + for (i = 0; i < smmu->num_mapping_groups; i++) {
>> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
>> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
>> + continue;
>> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
>> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
>> + smmu->smrs[i].valid = true;
>> + }[ 2.707729] arm-smmu: setting up rmr list on 0x4000
> [ 2.712598] arm-smmu: s2crs count is 0 smrs index 0x0
> [ 2.717638] arm-smmu: s2crs count is 0 smrs id is 0x4000
> [ 2.722939] arm-smmu: s2crs count is 0 smrs mask is 0x8000
> [ 2.728417] arm-smmu arm-smmu.0.auto: preserved 1 boot mapping
>
>> + }
>
> Then this code block was hit which is correct
>
>> + if (smmu->s2crs[i].count == 0) {
>> + smmu->smrs[i].id = sid;
>> + smmu->smrs[i].mask = ~0;
>> + smmu->smrs[i].valid = true;
>> + }
>
> The mask was causing the issue. If I think ammended that segment to read
> the mask as setup by the hardware everything was back to functioning both
> with and without disable_bypass set.
...so reading a mask from it doesn't sounds quite right.
Can you have a go with a corrected mask of '0' rather than all-1s and
see if that helps? My guess is that the mask of ~0 was causing multiple
matches in the SMRs which is 'UNPREDICTABLE'.
Sadly in my test setup there's only the one device behind the SMMU so
I didn't spot this (below patch works for me, but that's not saying
much).
Steve
--->8---
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 56db3d3238fc..44831d0c78e4 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -2079,7 +2079,7 @@ static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device *smmu)
continue;
if (smmu->s2crs[i].count == 0) {
smmu->smrs[i].id = sid;
- smmu->smrs[i].mask = ~0;
+ smmu->smrs[i].mask = 0;
smmu->smrs[i].valid = true;
}
smmu->s2crs[i].count++;
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