iommu/rockchip: Handle errors returned from PM framework

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")
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 054cd2c..4e0f9b6 100644 (file)
--- 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);