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    SubjectRe: [PATCH v2 13/17] driver core: Use device's fwnode to check if it is waiting for suppliers
    On 20-11-20 18:02:28, Saravana Kannan wrote:
    > To check if a device is still waiting for its supplier devices to be
    > added, we used to check if the devices is in a global
    > waiting_for_suppliers list. Since the global list will be deleted in
    > subsequent patches, this patch stops using this check.
    >
    > Instead, this patch uses a more device specific check. It checks if the
    > device's fwnode has any fwnode links that haven't been converted to
    > device links yet.
    >
    > Signed-off-by: Saravana Kannan <saravanak@google.com>
    > ---
    > drivers/base/core.c | 18 ++++++++----------
    > 1 file changed, 8 insertions(+), 10 deletions(-)
    >
    > diff --git a/drivers/base/core.c b/drivers/base/core.c
    > index 395dece1c83a..1873cecb0cc4 100644
    > --- a/drivers/base/core.c
    > +++ b/drivers/base/core.c
    > @@ -51,6 +51,7 @@ static DEFINE_MUTEX(wfs_lock);
    > static LIST_HEAD(deferred_sync);
    > static unsigned int defer_sync_state_count = 1;
    > static DEFINE_MUTEX(fwnode_link_lock);
    > +static bool fw_devlink_is_permissive(void);
    >
    > /**
    > * fwnode_link_add - Create a link between two fwnode_handles.
    > @@ -995,13 +996,13 @@ int device_links_check_suppliers(struct device *dev)
    > * Device waiting for supplier to become available is not allowed to
    > * probe.
    > */
    > - mutex_lock(&wfs_lock);
    > - if (!list_empty(&dev->links.needs_suppliers) &&
    > - dev->links.need_for_probe) {
    > - mutex_unlock(&wfs_lock);
    > + mutex_lock(&fwnode_link_lock);
    > + if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
    > + !fw_devlink_is_permissive()) {
    > + mutex_unlock(&fwnode_link_lock);

    Hi Saravana,

    First of, sorry for going back to this.

    There is a scenario where this check will not work and probably should
    work. It goes like this:

    A clock controller is not allowed to probe because it uses a clock from a child device of a
    consumer, like so:

    dispcc: clock-controller@af00000 {
    clocks = <&dsi0_phy 0>;
    };

    mdss: mdss@ae00000 {
    clocks = <&dispcc DISP_CC_MDSS_MDP_CLK>;

    dsi0_phy: dsi-phy@ae94400 {
    clocks = <&dispcc DISP_CC_MDSS_AHB_CLK>,
    };
    };

    This is a real scenario actually, but I stripped it down to the essentials.

    So, the dsi0_phy will be "device_add'ed" (through of_platform_populate) by the mdss probe.
    The mdss will probe defer waiting for the DISP_CC_MDSS_MDP_CLK, while
    the dispcc will probe defer waiting for the dsi0_phy (supplier).

    Basically, this 'supplier availability check' does not work when a supplier might
    be populated by a consumer of the device that is currently trying to probe.


    Abel


    > return -EPROBE_DEFER;
    > }
    > - mutex_unlock(&wfs_lock);
    > + mutex_unlock(&fwnode_link_lock);
    >
    > device_links_write_lock();
    >
    > @@ -1167,10 +1168,7 @@ static ssize_t waiting_for_supplier_show(struct device *dev,
    > bool val;
    >
    > device_lock(dev);
    > - mutex_lock(&wfs_lock);
    > - val = !list_empty(&dev->links.needs_suppliers)
    > - && dev->links.need_for_probe;
    > - mutex_unlock(&wfs_lock);
    > + val = !list_empty(&dev->fwnode->suppliers);
    > device_unlock(dev);
    > return sysfs_emit(buf, "%u\n", val);
    > }
    > @@ -2202,7 +2200,7 @@ static int device_add_attrs(struct device *dev)
    > goto err_remove_dev_groups;
    > }
    >
    > - if (fw_devlink_flags && !fw_devlink_is_permissive()) {
    > + if (fw_devlink_flags && !fw_devlink_is_permissive() && dev->fwnode) {
    > error = device_create_file(dev, &dev_attr_waiting_for_supplier);
    > if (error)
    > goto err_remove_dev_online;
    > --
    > 2.29.2.454.gaff20da3a2-goog
    >
    >

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