Re: [PATCH v4 0/8] Make fw_devlink=on more forgiving

[<Tudor.Ambarus@microchip.com>]

On 2/10/21 10:54 AM, Saravana Kannan wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Wed, Feb 10, 2021 at 12:19 AM <Tudor.Ambarus@microchip.com> wrote:
>>
>> Hi, Saravana,
>>
>> On 2/6/21 12:26 AM, Saravana Kannan wrote:
>>> There are a lot of devices/drivers where they never have a struct device
>>> created for them or the driver initializes the hardware without ever
>>> binding to the struct device.
>>>
>>> This series is intended to avoid any boot regressions due to such
>>> devices/drivers when fw_devlink=on and also address the handling of
>>> optional suppliers.
>>>
>>> Patch 1 and 2 addresses the issue of firmware nodes that look like
>>> they'll have struct devices created for them, but will never actually
>>> have struct devices added for them. For example, DT nodes with a
>>> compatible property that don't have devices added for them.
>>>
>>> Patch 3 and 4 allow for handling optional DT bindings.
>>>
>>> Patch 5 sets up a generic API to handle drivers that never bind with
>>> their devices.
>>>
>>> Patch 6 through 8 update different frameworks to use the new API.
>>>
>>> Thanks,
>>> Saravana
>>>
>>> Saravana Kannan (8):
>>>   driver core: fw_devlink: Detect supplier devices that will never be
>>>     added
>>>   of: property: Don't add links to absent suppliers
>>>   driver core: Add fw_devlink.strict kernel param
>>>   of: property: Add fw_devlink support for optional properties
>>>   driver core: fw_devlink: Handle suppliers that don't use driver core
>>>   irqdomain: Mark fwnodes when their irqdomain is added/removed
>>>   PM: domains: Mark fwnodes when their powerdomain is added/removed
>>>   clk: Mark fwnodes when their clock provider is added/removed
>>>
>>>  .../admin-guide/kernel-parameters.txt         |  5 ++
>>>  drivers/base/core.c                           | 58 ++++++++++++++++++-
>>>  drivers/base/power/domain.c                   |  2 +
>>>  drivers/clk/clk.c                             |  3 +
>>>  drivers/of/property.c                         | 16 +++--
>>>  include/linux/fwnode.h                        | 20 ++++++-
>>>  kernel/irq/irqdomain.c                        |  2 +
>>>  7 files changed, 98 insertions(+), 8 deletions(-)
>>>
>>
>> Even with this patch set applied, sama5d2_xplained can not boot.
>> Patch at [1] makes sama5d2_xplained boot again. Stephen applied it
>> to clk-next.
> 
> I'm glad you won't actually have any boot issues in 5.12, but the fact
> you need [1] with this series doesn't make a lot of sense to me
> because:
> 
> 1. The FWNODE_FLAG_INITIALIZED flag will be set for the clock fwnode
> in question way before any consumer devices are added.

Looks like in my case FWNODE_FLAG_INITIALIZED is not set, because
drivers/clk/at91/sama5d2.c uses of_clk_add_hw_provider().

> 2. Any consumer device added after (1) will stop trying to link to the
> clock device.
> 
> Are you somehow adding a consumer to the clock fwnode before (1)?
> 
> Can you try this patch without your clk fix? I was trying to avoid
> looping through a list, but looks like your case might somehow need
> it?
> 

I tried it, didn't solve my boot problem. The following patch makes the
sama5d2_xplained boot again, even without the patch from [1]:

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 27ff90eacb1f..9370e4dfecae 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4594,6 +4594,8 @@ int of_clk_add_hw_provider(struct device_node *np,
        if (ret < 0)
                of_clk_del_provider(np);
 
+       fwnode_dev_initialized(&np->fwnode, true);
+
        return ret;
 }
 EXPORT_SYMBOL_GPL(of_clk_add_hw_provider);

Cheers,
ta

> -Saravana
> 
> +++ b/drivers/base/core.c
> @@ -943,6 +943,31 @@ static void device_links_missing_supplier(struct
> device *dev)
>         }
>  }
> 
> +static int fw_devlink_check_suppliers(struct device *dev)
> +{
> +       struct fwnode_link *link;
> +       int ret = 0;
> +
> +       if (!dev->fwnode ||fw_devlink_is_permissive())
> +               return 0;
> +
> +       /*
> +        * Device waiting for supplier to become available is not allowed to
> +        * probe.
> +        */
> +       mutex_lock(&fwnode_link_lock);
> +       list_for_each_entry(link, &dev->fwnode->suppliers, c_hook) {
> +               if (link->supplier->flags & FWNODE_FLAG_INITIALIZED)
> +                       continue;
> +
> +               ret = -EPROBE_DEFER;
> +               break;
> +       }
> +       mutex_unlock(&fwnode_link_lock);
> +
> +       return ret;
> +}
> +
>  /**
>   * device_links_check_suppliers - Check presence of supplier drivers.
>   * @dev: Consumer device.
> @@ -964,21 +989,13 @@ int device_links_check_suppliers(struct device *dev)
>         struct device_link *link;
>         int ret = 0;
> 
> -       /*
> -        * Device waiting for supplier to become available is not allowed to
> -        * probe.
> -        */
> -       mutex_lock(&fwnode_link_lock);
> -       if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
> -           !fw_devlink_is_permissive()) {
> +       if (fw_devlink_check_suppliers(dev)) {
>                 dev_dbg(dev, "probe deferral - wait for supplier %pfwP\n",
>                         list_first_entry(&dev->fwnode->suppliers,
>                         struct fwnode_link,
>                         c_hook)->supplier);
> -               mutex_unlock(&fwnode_link_lock);
>                 return -EPROBE_DEFER;
>         }
> -       mutex_unlock(&fwnode_link_lock);
> 
>         device_links_write_lock();
> 
> 
> 
>>
>> Cheers,
>> ta
>>
>> [1] https://lore.kernel.org/lkml/20210203154332.470587-1-tudor.ambarus@microchip.com/