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Subject[PATCH 1/2] iommu/rockchip: Handle errors returned from PM framework
Date
pm_runtime_get_if_in_use can fail: either PM has been disabled
altogether (-EINVAL), or the device hasn't been enabled yet (0).
Sadly, the Rockchip IOMMU driver tends to conflate the two things
by considering a non-zero return value as successful.

This has the consequence of hiding other bugs, so let's handle this
case throughout the driver, with a WARN_ON_ONCE so that we can try
and work out what happened.

Fixes: 0f181d3cf7d98 ("iommu/rockchip: Add runtime PM support")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
drivers/iommu/rockchip-iommu.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 054cd2c8e9c8..4e0f9b61cd7f 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -521,10 +521,11 @@ static irqreturn_t rk_iommu_irq(int irq, void *dev_id)
u32 int_status;
dma_addr_t iova;
irqreturn_t ret = IRQ_NONE;
- int i;
+ int i, err;

- if (WARN_ON(!pm_runtime_get_if_in_use(iommu->dev)))
- return 0;
+ err = pm_runtime_get_if_in_use(iommu->dev);
+ if (WARN_ON_ONCE(err <= 0))
+ return ret;

if (WARN_ON(clk_bulk_enable(iommu->num_clocks, iommu->clocks)))
goto out;
@@ -620,11 +621,15 @@ static void rk_iommu_zap_iova(struct rk_iommu_domain *rk_domain,
spin_lock_irqsave(&rk_domain->iommus_lock, flags);
list_for_each(pos, &rk_domain->iommus) {
struct rk_iommu *iommu;
+ int ret;

iommu = list_entry(pos, struct rk_iommu, node);

/* Only zap TLBs of IOMMUs that are powered on. */
- if (pm_runtime_get_if_in_use(iommu->dev)) {
+ ret = pm_runtime_get_if_in_use(iommu->dev);
+ if (WARN_ON_ONCE(ret < 0))
+ continue;
+ if (ret) {
WARN_ON(clk_bulk_enable(iommu->num_clocks,
iommu->clocks));
rk_iommu_zap_lines(iommu, iova, size);
@@ -891,6 +896,7 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
struct rk_iommu *iommu;
struct rk_iommu_domain *rk_domain = to_rk_domain(domain);
unsigned long flags;
+ int ret;

/* Allow 'virtual devices' (eg drm) to detach from domain */
iommu = rk_iommu_from_dev(dev);
@@ -909,7 +915,9 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
list_del_init(&iommu->node);
spin_unlock_irqrestore(&rk_domain->iommus_lock, flags);

- if (pm_runtime_get_if_in_use(iommu->dev)) {
+ ret = pm_runtime_get_if_in_use(iommu->dev);
+ WARN_ON_ONCE(ret < 0);
+ if (ret > 0) {
rk_iommu_disable(iommu);
pm_runtime_put(iommu->dev);
}
@@ -946,7 +954,8 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
list_add_tail(&iommu->node, &rk_domain->iommus);
spin_unlock_irqrestore(&rk_domain->iommus_lock, flags);

- if (!pm_runtime_get_if_in_use(iommu->dev))
+ ret = pm_runtime_get_if_in_use(iommu->dev);
+ if (!ret || WARN_ON_ONCE(ret < 0))
return 0;

ret = rk_iommu_enable(iommu);
--
2.18.0
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