On 2/1/2018 5:03 PM, Sricharan R wrote:
Hi Robin,

On 1/31/2018 6:36 PM, Robin Murphy wrote:
On 19/01/18 11:43, Vivek Gautam wrote:
From: Sricharan R <sricha...@codeaurora.org>

The smmu device probe/remove and add/remove master device callbacks
gets called when the smmu is not linked to its master, that is without
the context of the master device. So calling runtime apis in those places

Signed-off-by: Sricharan R <sricha...@codeaurora.org>
[vivek: Cleanup pm runtime calls]
Signed-off-by: Vivek Gautam <vivek.gau...@codeaurora.org>
   drivers/iommu/arm-smmu.c | 45 +++++++++++++++++++++++++++++++++++++++++----
   1 file changed, 41 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 21acffe91a1c..95478bfb182c 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -914,11 +914,15 @@ static void arm_smmu_destroy_domain_context(struct 
iommu_domain *domain)
       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
       struct arm_smmu_device *smmu = smmu_domain->smmu;
       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
-    int irq;
+    int ret, irq;
         if (!smmu || domain->type == IOMMU_DOMAIN_IDENTITY)
   +    ret = pm_runtime_get_sync(smmu->dev);
+    if (ret)
+        return;
        * Disable the context bank and free the page tables before freeing
        * it.
@@ -933,6 +937,8 @@ static void arm_smmu_destroy_domain_context(struct 
iommu_domain *domain)
       __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
+    pm_runtime_put_sync(smmu->dev);
     static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
@@ -1408,12 +1414,20 @@ static int arm_smmu_add_device(struct device *dev)
       while (i--)
           cfg->smendx[i] = INVALID_SMENDX;
   -    ret = arm_smmu_master_alloc_smes(dev);
+    ret = pm_runtime_get_sync(smmu->dev);
       if (ret)
           goto out_cfg_free;
   +    ret = arm_smmu_master_alloc_smes(dev);
+    if (ret) {
+        pm_runtime_put_sync(smmu->dev);
+        goto out_cfg_free;
Please keep to the existing pattern and put this on the cleanup path with a new 
label, rather than inline.

+    }
       iommu_device_link(&smmu->iommu, dev);
   +    pm_runtime_put_sync(smmu->dev);
       return 0;
@@ -1428,7 +1442,7 @@ static void arm_smmu_remove_device(struct device *dev)
       struct iommu_fwspec *fwspec = dev->iommu_fwspec;
       struct arm_smmu_master_cfg *cfg;
       struct arm_smmu_device *smmu;
+    int ret;
         if (!fwspec || fwspec->ops != &arm_smmu_ops)
@@ -1436,8 +1450,21 @@ static void arm_smmu_remove_device(struct device *dev)
       cfg  = fwspec->iommu_priv;
       smmu = cfg->smmu;
   +    /*
+     * The device link between the master device and
+     * smmu is already purged at this point.
+     * So enable the power to smmu explicitly.
+     */
I don't understand this comment, especially since we don't even introduce 
device links until the following patch... :/

  This is because the core device_del callback, does a device_links_purge for 
that device,
  before calling the remove_device notifier. As a result, have to explicitly 
turn on the
  power to iommu. Probably the comment should be removed, rest of the places we 
  explain why we are turning on explicitly.

Yes, will remove the comment here.

+    ret = pm_runtime_get_sync(smmu->dev);
+    if (ret)
+        return;
       iommu_device_unlink(&smmu->iommu, dev);
+    pm_runtime_put_sync(smmu->dev);
@@ -2130,6 +2157,14 @@ static int arm_smmu_device_probe(struct platform_device 
       if (err)
           return err;
   +    platform_set_drvdata(pdev, smmu);
+    pm_runtime_enable(dev);
+    err = pm_runtime_get_sync(dev);
+    if (err)
+        return err;
       err = arm_smmu_device_cfg_probe(smmu);
       if (err)
           return err;
@@ -2171,9 +2206,9 @@ static int arm_smmu_device_probe(struct platform_device 
           return err;
   -    platform_set_drvdata(pdev, smmu);
+    pm_runtime_put_sync(dev);
        * For ACPI and generic DT bindings, an SMMU will be probed before
@@ -2212,6 +2247,8 @@ static int arm_smmu_device_remove(struct platform_device 
         /* Turn the thing off */
       writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
+    pm_runtime_force_suspend(smmu->dev);
Why do we need this? I guess it might be a Qualcomm-ism as I don't see anyone 
else calling it from .remove other than a couple of other qcom_* drivers. Given 
that we only get here during system shutdown (or the root user intentionally 
pissing about with driver unbinding), it doesn't seem like a point where power 
saving really matters all that much.

I'd also naively expect that anything this device was the last consumer off 
would get turned off by core code anyway once it's removed, but maybe things 
aren't that slick; I dunno :/
  hmm, that should not be needed. with turning of all consumers taken care by 
device_link code before
  the supplier (iommu) remove gets called should ensure that. So the above 
force_suspend should
  not be needed/can be removed. But one more thing is, we do touch the register 
in the above code.
  So that should require a additional get/put sync around that writel.

Possibly we can replace the force_suspend() with a pm_runtime_disable() to complement pm_runtime_enable in the probe. I will test the scenario where we are writing the SMMU register in .remove path.



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