Re: [PATCH v3] treewide: Fix probing of devices in DT overlays
From: Saravana Kannan
Date: Thu Mar 30 2023 - 15:55:11 EST
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
>