On 2020-10-17 05:39, Bjorn Andersson wrote:
The firmware found in some Qualcomm platforms intercepts writes to S2CR
in order to replace bypass type streams with fault; and ignore S2CR
updates of type fault.
Detect this behavior and implement a custom write_s2cr function in order
to trick the firmware into supporting bypass streams by the means of
configuring the stream for translation using a reserved and disabled
context bank.
Also circumvent the problem of configuring faulting streams by
configuring the stream as bypass.
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
Changes since v3:
- Move the reservation of the "identity context bank" to the Qualcomm specific
implementation.
- Implement the S2CR quirk with the newly introduced write_s2cr callback.
drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 68 ++++++++++++++++++++++
1 file changed, 68 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 0089048342dd..c0f42d6a6e01 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -10,8 +10,14 @@
struct qcom_smmu {
struct arm_smmu_device smmu;
+ bool bypass_cbndx;
Nit: variables named "*ndx" usually hold an actual index value. If it's
just a flag then maybe name it something like "use_bypass_context"?
};
+static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
+{
+ return container_of(smmu, struct qcom_smmu, smmu);
+}
+
static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
{ .compatible = "qcom,adreno" },
{ .compatible = "qcom,mdp4" },
@@ -25,9 +31,32 @@ static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
{
+ unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1);
+ struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
+ u32 reg;
u32 smr;
int i;
+ /*
+ * With some firmware versions writes to S2CR of type FAULT are
+ * ignored, and writing BYPASS will end up written as FAULT in the
+ * register. Perform a write to S2CR to detect if this is the case and
+ * if so reserve a context bank to emulate bypass streams.
+ */
+ reg = FIELD_PREP(ARM_SMMU_S2CR_TYPE, S2CR_TYPE_BYPASS) |
+ FIELD_PREP(ARM_SMMU_S2CR_CBNDX, 0xff) |
+ FIELD_PREP(ARM_SMMU_S2CR_PRIVCFG, S2CR_PRIVCFG_DEFAULT);
+ arm_smmu_gr0_write(smmu, last_s2cr, reg);
+ reg = arm_smmu_gr0_read(smmu, last_s2cr);
+ if (FIELD_GET(ARM_SMMU_S2CR_TYPE, reg) != S2CR_TYPE_BYPASS) {
+ qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
Oh, so maybe the name is in fact OK but the type is wrong :/
I guess this does happens to work out, but for the wrong reason...
+
+ set_bit(qsmmu->bypass_cbndx, smmu->context_map);
+
+ reg = FIELD_PREP(ARM_SMMU_CBAR_TYPE, CBAR_TYPE_S1_TRANS_S2_BYPASS);
+ arm_smmu_gr1_write(smmu, ARM_SMMU_GR1_CBAR(qsmmu->bypass_cbndx), reg);
+ }
+
for (i = 0; i < smmu->num_mapping_groups; i++) {
smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
@@ -46,6 +75,44 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
return 0;
}
+static void qcom_smmu_write_s2cr(struct arm_smmu_device *smmu, int idx)
+{
+ struct arm_smmu_s2cr *s2cr = smmu->s2crs + idx;
+ struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
+ u32 cbndx = s2cr->cbndx;
+ u32 type = s2cr->type;
+ u32 reg;
+
+ if (qsmmu->bypass_cbndx) {
Note that if we are talking indices here then 0 would be perfectly valid
in general. This works out OK in practice given that we're always
reserving the last implemented context above, and if we ever *did* only
have one such that index 0 is the last then we're going to have a bad
time either way, but it's not necessarily the most obvious.
+ if (type == S2CR_TYPE_BYPASS) {
+ /*
+ * Firmware with quirky S2CR handling will substitute
+ * BYPASS writes with FAULT, so point the stream to the
+ * reserved context bank and ask for translation on the
+ * stream
+ */
+ type = S2CR_TYPE_TRANS;
+ cbndx = qsmmu->bypass_cbndx;
+ } else if (type == S2CR_TYPE_FAULT) {
+ /*
+ * Firmware with quirky S2CR handling will ignore FAULT
+ * writes, so trick it to write FAULT by asking for a
+ * BYPASS.
+ */
+ type = S2CR_TYPE_BYPASS;
Ha, that's brilliant :)
+ cbndx = 0xff;
+ }
+ }
+
+ reg = FIELD_PREP(ARM_SMMU_S2CR_TYPE, type) |
+ FIELD_PREP(ARM_SMMU_S2CR_CBNDX, cbndx) |
+ FIELD_PREP(ARM_SMMU_S2CR_PRIVCFG, s2cr->privcfg);
+
+ if (smmu->features & ARM_SMMU_FEAT_EXIDS && smmu->smrs && smmu->smrs[idx].valid)
+ reg |= ARM_SMMU_S2CR_EXIDVALID;
Does any of your hardware actually have EXIDS implemented? No big deal
if you only want this here "just in case", I'm just curious as I was
under then impression that it was essentially a ThunderX special.
Other than sorting out bypass_cbndx one way or the other, overall this
is now looking about as nice as it ever could - thanks for persevering!
Robin.
+ arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_S2CR(idx), reg);
+}
+
static int qcom_smmu_def_domain_type(struct device *dev)
{
const struct of_device_id *match =
@@ -87,6 +154,7 @@ static const struct arm_smmu_impl qcom_smmu_impl = {
.cfg_probe = qcom_smmu_cfg_probe,
.def_domain_type = qcom_smmu_def_domain_type,
.reset = qcom_smmu500_reset,
+ .write_s2cr = qcom_smmu_write_s2cr,
};
struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu)
