From mboxrd@z Thu Jan 1 00:00:00 1970 From: shijie.huang@arm.com (Huang Shijie) Date: Tue, 12 Jan 2016 10:15:05 +0800 Subject: [PATCH] iommu/arm-smmu: add a shortcut when the @dev_node is NULL Message-ID: <1452564905-2662-1-git-send-email-shijie.huang@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org When a device is added to a bus, it will trigger the chain notifier hook, such as iommu_bus_notifier. The find_smmu_for_device() can be called here. In some cases, the @device_node can be NULL. For example, when the device is one of the following: alarmtime, serial, rtc or snd_soc. This patch adds a shortcut for the code when the @device_node is NULL. In my juno-r1 board, the boot time can be faster by 0.004014s. Signed-off-by: Huang Shijie --- drivers/iommu/arm-smmu.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c index 59ee4b8..6724a46 100644 --- a/drivers/iommu/arm-smmu.c +++ b/drivers/iommu/arm-smmu.c @@ -506,6 +506,9 @@ static struct arm_smmu_device *find_smmu_for_device(struct device *dev) struct arm_smmu_master *master = NULL; struct device_node *dev_node = dev_get_dev_node(dev); + if (!dev_node) + return NULL; + spin_lock(&arm_smmu_devices_lock); list_for_each_entry(smmu, &arm_smmu_devices, list) { master = find_smmu_master(smmu, dev_node); -- 2.5.0