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SubjectRe: [PATCH] driver core: Avoid pointless deferred probe attempts
On Thu, Feb 18, 2021 at 12:51 AM Saravana Kannan <saravanak@google.com> wrote:
>
> There's no point in adding a device to the deferred probe list if we
> know for sure that it doesn't have a matching driver. So, check if a
> device can match with a driver before adding it to the deferred probe
> list.

What if a matching driver module loads in the meantime?

>
> Signed-off-by: Saravana Kannan <saravanak@google.com>
> ---
> Geert,
>
> Can you give this a shot for your I2C DMA issue with fw_devlink=on?
>
> -Saravana
>
> drivers/base/dd.c | 6 ++++++
> include/linux/device.h | 4 ++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 9179825ff646..f18963f42e21 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -123,6 +123,9 @@ static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
>
> void driver_deferred_probe_add(struct device *dev)
> {
> + if (!dev->can_match)
> + return;
> +
> mutex_lock(&deferred_probe_mutex);
> if (list_empty(&dev->p->deferred_probe)) {
> dev_dbg(dev, "Added to deferred list\n");
> @@ -726,6 +729,7 @@ static int driver_probe_device(struct device_driver *drv, struct device *dev)
> if (!device_is_registered(dev))
> return -ENODEV;
>
> + dev->can_match = true;
> pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
> drv->bus->name, __func__, dev_name(dev), drv->name);
>
> @@ -829,6 +833,7 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
> return 0;
> } else if (ret == -EPROBE_DEFER) {
> dev_dbg(dev, "Device match requests probe deferral\n");
> + dev->can_match = true;
> driver_deferred_probe_add(dev);
> } else if (ret < 0) {
> dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> @@ -1064,6 +1069,7 @@ static int __driver_attach(struct device *dev, void *data)
> return 0;
> } else if (ret == -EPROBE_DEFER) {
> dev_dbg(dev, "Device match requests probe deferral\n");
> + dev->can_match = true;
> driver_deferred_probe_add(dev);
> } else if (ret < 0) {
> dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 7619a84f8ce4..1f9cc1ba78bc 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -438,6 +438,9 @@ struct dev_links_info {
> * @state_synced: The hardware state of this device has been synced to match
> * the software state of this device by calling the driver/bus
> * sync_state() callback.
> + * @can_match: The device has matched with a driver at least once or it is in
> + * a bus (like AMBA) which can't check for matching drivers until
> + * other devices probe successfully.
> * @dma_coherent: this particular device is dma coherent, even if the
> * architecture supports non-coherent devices.
> * @dma_ops_bypass: If set to %true then the dma_ops are bypassed for the
> @@ -544,6 +547,7 @@ struct device {
> bool offline:1;
> bool of_node_reused:1;
> bool state_synced:1;
> + bool can_match:1;
> #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
> --

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