Re: [PATCH v5 3/3] iommu/arm-smmu-qcom: Implement S2CR quirk
On 2020-10-19 19:23, 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
---
Changes since v4:
- Made the bypass_cbndx an integer...
- Separated out the "quirk enabled or not" into a bool, rather than reusing
(the valid) context bank 0 to represent this.
- Dropped the unused EXIDS handling.
drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 67 ++
1 file changed, 67 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 48627fcf6bed..66ba4870659f 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -10,8 +10,15 @@
struct qcom_smmu {
struct arm_smmu_device smmu;
+ bool bypass_quirk;
+ u8 bypass_cbndx;
};
+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 +32,33 @@ 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_quirk = true;
+ qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
FWIW you could arguably just calculate that at point of use. Or store
the index as an int and use a negative value to indicate when it's
irrelevant to save the separate flag. But there's also nothing *wrong*
with having it all spelled out, so regardless,
Acked-by: Robin Murphy
Cheers,
Robin.
+
+ 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));
@@ -45,6 +76,41 @@ 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_quirk) {
+ 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;
+ 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);
+ arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_S2CR(idx), reg);
+}
+
static int
[PATCH v5 3/3] iommu/arm-smmu-qcom: Implement S2CR quirk
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
---
Changes since v4:
- Made the bypass_cbndx an integer...
- Separated out the "quirk enabled or not" into a bool, rather than reusing
(the valid) context bank 0 to represent this.
- Dropped the unused EXIDS handling.
drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 67 ++
1 file changed, 67 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 48627fcf6bed..66ba4870659f 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -10,8 +10,15 @@
struct qcom_smmu {
struct arm_smmu_device smmu;
+ bool bypass_quirk;
+ u8 bypass_cbndx;
};
+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 +32,33 @@ 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_quirk = true;
+ qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
+
+ 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));
@@ -45,6 +76,41 @@ 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_quirk) {
+ 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;
+ 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);
+ 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 =
@@ -86,6 +152,7 @@ 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
