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Commit 8cf6c69d authored by Veera Sundaram Sankaran's avatar Veera Sundaram Sankaran
Browse files

msm: mdss: protect iommu attached status variable with iommu_lock 



Commit dd7ad27e ("msm: mdss: fix
race condition between iommu attach and sending DCS cmds") protected
the iommu attach/detach to fix possible race condition between the
display thread and DCS cmd sending from ESD or some other thread with
iommu_lock. But this still leaves possibility of race condition based
on iommu_attached status flag.
  -> Display thread finishes the attach and releases the iommu lock
  -> DCS cmd thread gets the iommu lock and checks iommu_attached
     status before display thread could change it.
Protect the iommu_attached status variable along with iommu
attach/detach to avoid such cases.

Change-Id: I42d0ced5cbfd741cf02ad71c80c4f01dde37f647
Signed-off-by: default avatarVeera Sundaram Sankaran <veeras@codeaurora.org>
parent 034326e6

drivers/video/msm/mdss/mdss_smmu.c

+0 −6
Original line number Diff line number Diff line
@@ -172,7 +172,6 @@ static int mdss_smmu_attach_v2(struct mdss_data_type *mdata) 
	struct mdss_smmu_client *mdss_smmu;

	int i, rc = 0;



	mutex_lock(&mdp_iommu_lock);

	for (i = 0; i < MDSS_IOMMU_MAX_DOMAIN; i++) {

		if (!mdss_smmu_is_valid_domain_type(mdata, i))

			continue;
@@ -204,11 +203,9 @@ static int mdss_smmu_attach_v2(struct mdss_data_type *mdata) 
			}

		} else {

			pr_err("iommu device not attached for domain[%d]\n", i);

			mutex_unlock(&mdp_iommu_lock);

			return -ENODEV;

		}

	}

	mutex_unlock(&mdp_iommu_lock);



	return 0;
@@ -221,7 +218,6 @@ err: 
			mdss_smmu->domain_attached = false;

		}

	}

	mutex_unlock(&mdp_iommu_lock);



	return rc;

}
@@ -237,7 +233,6 @@ static int mdss_smmu_detach_v2(struct mdss_data_type *mdata) 
	struct mdss_smmu_client *mdss_smmu;

	int i;



	mutex_lock(&mdp_iommu_lock);

	for (i = 0; i < MDSS_IOMMU_MAX_DOMAIN; i++) {

		if (!mdss_smmu_is_valid_domain_type(mdata, i))

			continue;
@@ -246,7 +241,6 @@ static int mdss_smmu_detach_v2(struct mdss_data_type *mdata) 
		if (mdss_smmu && mdss_smmu->dev && !mdss_smmu->handoff_pending)

			mdss_smmu_enable_power(mdss_smmu, false);

	}

	mutex_unlock(&mdp_iommu_lock);



	return 0;

}

drivers/video/msm/mdss/mdss_smmu.h

+21 −6
Original line number Diff line number Diff line
@@ -119,18 +119,26 @@ static inline int mdss_smmu_attach(struct mdss_data_type *mdata) 
{

	int rc;



	mdata->mdss_util->iommu_lock();

	MDSS_XLOG(mdata->iommu_attached);



	if (mdata->iommu_attached) {

		pr_debug("mdp iommu already attached\n");

		return 0;

		rc = 0;

		goto end;

	}



	if (!mdata->smmu_ops.smmu_attach)

		return -ENOSYS;

	if (!mdata->smmu_ops.smmu_attach) {

		rc = -ENOSYS;

		goto end;

	}



	rc =  mdata->smmu_ops.smmu_attach(mdata);

	if (!rc)

		mdata->iommu_attached = true;



end:

	mdata->mdss_util->iommu_unlock();

	return rc;

}
@@ -138,19 +146,26 @@ static inline int mdss_smmu_detach(struct mdss_data_type *mdata) 
{

	int rc;



	mdata->mdss_util->iommu_lock();

	MDSS_XLOG(mdata->iommu_attached);



	if (!mdata->iommu_attached) {

		pr_debug("mdp iommu already dettached\n");

		return 0;

		rc = 0;

		goto end;

	}



	if (!mdata->smmu_ops.smmu_detach)

		return -ENOSYS;

	if (!mdata->smmu_ops.smmu_detach) {

		rc = -ENOSYS;

		goto end;

	}



	rc = mdata->smmu_ops.smmu_detach(mdata);

	if (!rc)

		mdata->iommu_attached = false;



end:

	mdata->mdss_util->iommu_unlock();

	return rc;

}