Re: [PATCH v3] treewide: Fix probing of devices in DT overlays

[Saravana Kannan <saravanak@xxxxxxxxxx>]

On Thu, Mar 30, 2023 at 6:26 AM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
>
> When loading a DT overlay that creates a device, the device is not
> probed, unless the DT overlay is unloaded and reloaded again.
>
> After the recent refactoring to improve fw_devlink, it no longer depends
> on the "compatible" property to identify which device tree nodes will
> become struct devices.   fw_devlink now picks up dangling consumers
> (consumers pointing to descendent device tree nodes of a device that
> aren't converted to child devices) when a device is successfully bound
> to a driver.  See __fw_devlink_pickup_dangling_consumers().
>
> However, during DT overlay, a device's device tree node can have
> sub-nodes added/removed without unbinding/rebinding the driver.  This
> difference in behavior between the normal device instantiation and
> probing flow vs. the DT overlay flow has a bunch of implications that
> are pointed out elsewhere[1].  One of them is that the fw_devlink logic
> to pick up dangling consumers is never exercised.
>
> This patch solves the fw_devlink issue by marking all DT nodes added by
> DT overlays with FWNODE_FLAG_NOT_DEVICE (fwnode that won't become
> device), and by clearing the flag when a struct device is actually
> created for the DT node.  This way, fw_devlink knows not to have
> consumers waiting on these newly added DT nodes, and to propagate the
> dependency to an ancestor DT node that has the corresponding struct
> device.
>
> Based on a patch by Saravana Kannan, which covered only platform and spi
> devices.

Doesn't make sense to give a Reviewed-by to something I partially wrote, so:

Acked-by: Saravana Kannan <saravanak@xxxxxxxxxx>

Thanks for making sure this is fixed Geert!

-Saravana

>
> [1] https://lore.kernel.org/r/CAGETcx_bkuFaLCiPrAWCPQz+w79ccDp6=9e881qmK=vx3hBMyg@xxxxxxxxxxxxxx
>
> Fixes: 4a032827daa89350 ("of: property: Simplify of_link_to_phandle()")
> Link: https://lore.kernel.org/r/CAGETcx_+rhHvaC_HJXGrr5_WAd2+k5f=rWYnkCZ6z5bGX-wj4w@xxxxxxxxxxxxxx
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Acked-by: Mark Brown <broonie@xxxxxxxxxx>
> Acked-by: Wolfram Sang <wsa@xxxxxxxxxx> # for I2C
> ---
> v3:
>   - Add Acked-by,
>   - s/instantiate/probe/,
>   - Improve commit description,
>   - Add comment before clearing FWNODE_FLAG_NOT_DEVICE,
>
> v2:
>   - Add Acked-by,
>   - Drop RFC.
> ---
>  drivers/bus/imx-weim.c    | 6 ++++++
>  drivers/i2c/i2c-core-of.c | 5 +++++
>  drivers/of/dynamic.c      | 1 +
>  drivers/of/platform.c     | 5 +++++
>  drivers/spi/spi.c         | 5 +++++
>  5 files changed, 22 insertions(+)
>
> diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
> index 36d42484142aede2..cf463c1d2102c6fb 100644
> --- a/drivers/bus/imx-weim.c
> +++ b/drivers/bus/imx-weim.c
> @@ -329,6 +329,12 @@ static int of_weim_notify(struct notifier_block *nb, unsigned long action,
>                                  "Failed to setup timing for '%pOF'\n", rd->dn);
>
>                 if (!of_node_check_flag(rd->dn, OF_POPULATED)) {
> +                       /*
> +                        * Clear the flag before adding the device so that
> +                        * fw_devlink doesn't skip adding consumers to this
> +                        * device.
> +                        */
> +                       rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
>                         if (!of_platform_device_create(rd->dn, NULL, &pdev->dev)) {
>                                 dev_err(&pdev->dev,
>                                         "Failed to create child device '%pOF'\n",
> diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
> index aa93467784c29c89..5c137638689799c8 100644
> --- a/drivers/i2c/i2c-core-of.c
> +++ b/drivers/i2c/i2c-core-of.c
> @@ -178,6 +178,11 @@ static int of_i2c_notify(struct notifier_block *nb, unsigned long action,
>                         return NOTIFY_OK;
>                 }
>
> +               /*
> +                * Clear the flag before adding the device so that fw_devlink
> +                * doesn't skip adding consumers to this device.
> +                */
> +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
>                 client = of_i2c_register_device(adap, rd->dn);
>                 if (IS_ERR(client)) {
>                         dev_err(&adap->dev, "failed to create client for '%pOF'\n",
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index 07d93753b12f5f4d..e311d406b1705306 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -226,6 +226,7 @@ static void __of_attach_node(struct device_node *np)
>         np->sibling = np->parent->child;
>         np->parent->child = np;
>         of_node_clear_flag(np, OF_DETACHED);
> +       np->fwnode.flags |= FWNODE_FLAG_NOT_DEVICE;
>  }
>
>  /**
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index b2bd2e783445dd78..78ae8418744905c9 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -737,6 +737,11 @@ static int of_platform_notify(struct notifier_block *nb,
>                 if (of_node_check_flag(rd->dn, OF_POPULATED))
>                         return NOTIFY_OK;
>
> +               /*
> +                * Clear the flag before adding the device so that fw_devlink
> +                * doesn't skip adding consumers to this device.
> +                */
> +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
>                 /* pdev_parent may be NULL when no bus platform device */
>                 pdev_parent = of_find_device_by_node(rd->dn->parent);
>                 pdev = of_platform_device_create(rd->dn, NULL,
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 37a7be6c5a44c8f9..a12420e28640bbd4 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -4504,6 +4504,11 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action,
>                         return NOTIFY_OK;
>                 }
>
> +               /*
> +                * Clear the flag before adding the device so that fw_devlink
> +                * doesn't skip adding consumers to this device.
> +                */
> +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
>                 spi = of_register_spi_device(ctlr, rd->dn);
>                 put_device(&ctlr->dev);
>
> --
> 2.34.1
>