iommu/arm-smmu-qcom: Make set_stall work when the device is on

Up until now we have only called the set_stall callback during
initialization when the device is off. But we will soon start calling it
to temporarily disable stall-on-fault when the device is on, so handle
that by checking if the device is on and writing SCTLR.

Signed-off-by: Connor Abbott <[e-mail]>
Reviewed-by: Rob Clark <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[will: Fix "mixed declarations and code" warning from sparse]
Signed-off-by: Will Deacon <[e-mail]>

drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c

···
 {
 	struct arm_smmu_domain *smmu_domain = (void *)cookie;
 	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
-	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu_domain->smmu);
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
+	u32 mask = BIT(cfg->cbndx);
+	bool stall_changed = !!(qsmmu->stall_enabled & mask) != enabled;
+	unsigned long flags;
 
 	if (enabled)
-		qsmmu->stall_enabled |= BIT(cfg->cbndx);
+		qsmmu->stall_enabled |= mask;
 	else
-		qsmmu->stall_enabled &= ~BIT(cfg->cbndx);
+		qsmmu->stall_enabled &= ~mask;
+
+	/*
+	 * If the device is on and we changed the setting, update the register.
+	 * The spec pseudocode says that CFCFG is resampled after a fault, and
+	 * we believe that no implementations cache it in the TLB, so it should
+	 * be safe to change it without a TLB invalidation.
+	 */
+	if (stall_changed && pm_runtime_get_if_active(smmu->dev) > 0) {
+		u32 reg;
+
+		spin_lock_irqsave(&smmu_domain->cb_lock, flags);
+		reg = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_SCTLR);
+
+		if (enabled)
+			reg |= ARM_SMMU_SCTLR_CFCFG;
+		else
+			reg &= ~ARM_SMMU_SCTLR_CFCFG;
+
+		arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_SCTLR, reg);
+		spin_unlock_irqrestore(&smmu_domain->cb_lock, flags);
+
+		pm_runtime_put_autosuspend(smmu->dev);
+	}
 }
 
 static void qcom_adreno_smmu_set_prr_bit(const void *cookie, bool set)

include/linux/adreno-smmu-priv.h

···
  *                 TTBR0 translation is enabled with the specified cfg
  * @get_fault_info: Called by the GPU fault handler to get information about
  *                  the fault
- * @set_stall:     Configure whether stall on fault (CFCFG) is enabled.  Call
- *                 before set_ttbr0_cfg().  If stalling on fault is enabled,
- *                 the GPU driver must call resume_translation()
+ * @set_stall:     Configure whether stall on fault (CFCFG) is enabled. If
+ *                 stalling on fault is enabled, the GPU driver must call
+ *                 resume_translation()
  * @resume_translation: Resume translation after a fault
  *
  * @set_prr_bit:   [optional] Configure the GPU's Partially Resident