Re: [PATCH v2] treewide: Fix instantiation of devices in DT overlays
From: Saravana Kannan <hidden>
Date: 2023-03-29 19:50:03
Also in:
linux-devicetree, linux-i2c, linux-renesas-soc, linux-spi, lkml
On Fri, Mar 24, 2023 at 2:30 AM Geert Uytterhoeven [off-list ref] wrote:
I saw all the other replies. Let me give more details on the commit text and inline comments so it's clearer and not a "he said he said"
When loading a DT overlay that creates a device, the device is not instantiated,
IIRC I think the devices are instantiated, but not probed.
unless the DT overlay is unloaded and reloaded again. Saravana explains: Basically for all overlays (I hope the function is only used for overlays) we assume all nodes are NOT devices until they actually get added as a device.
This comment was about what the patch is doing. I think a better commit text would be something like below. Feel free to reword as you see fit. After the recent refactor to improve fw_devlink[1], it no longer depends on "compatible" property to identify which device tree nodes will become struct device. 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[2]. 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 overlay with FWNODE_FLAG_NOT_DEVICE (fwnode that won't become device) and then 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 corresponding struct device. [1] - https://lore.kernel.org/lkml/20230207014207.1678715-1-saravanak@google.com/ (local) [2] - https://lore.kernel.org/lkml/CAGETcx_bkuFaLCiPrAWCPQz+w79ccDp6=9e881qmK=vx3hBMyg@mail.gmail.com/#t (local)
Based on a patch by Saravana Kannan, which covered only platform and spi devices.
You can keep this in the commit text.
quoted hunk ↗ jump to hunk
Fixes: 4a032827daa89350 ("of: property: Simplify of_link_to_phandle()") Link: https://lore.kernel.org/r/CAGETcx_+rhHvaC_HJXGrr5_WAd2+k5f=rWYnkCZ6z5bGX-wj4w@mail.gmail.com (local) Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Mark Brown <broonie@kernel.org> --- v2: - Add Acked-by, - Drop RFC. --- drivers/bus/imx-weim.c | 1 + drivers/i2c/i2c-core-of.c | 1 + drivers/of/dynamic.c | 1 + drivers/of/platform.c | 1 + drivers/spi/spi.c | 1 + 5 files changed, 5 insertions(+)diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c index 36d42484142aede2..898e23a4231400fa 100644 --- a/drivers/bus/imx-weim.c +++ b/drivers/bus/imx-weim.c@@ -329,6 +329,7 @@ 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)) {
It's important this flag clearing is done before the device is added. So, can you please add a comment before all these clear flag lines that's something like: /* Clear the flag before adding the device so that fw_devlink doesn't skip adding consumers to this device. */ Thanks, Saravana
quoted hunk ↗ jump to hunk
+ 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..303f9003562eed3d 100644 --- a/drivers/i2c/i2c-core-of.c +++ b/drivers/i2c/i2c-core-of.c@@ -178,6 +178,7 @@ static int of_i2c_notify(struct notifier_block *nb, unsigned long action, return NOTIFY_OK; } + 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..17c92cbfb62ee3ef 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c@@ -737,6 +737,7 @@ static int of_platform_notify(struct notifier_block *nb, if (of_node_check_flag(rd->dn, OF_POPULATED)) return NOTIFY_OK; + 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 8e8af148b1dc371e..66ac67580d2a473b 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c@@ -4527,6 +4527,7 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action, return NOTIFY_OK; } + rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE; spi = of_register_spi_device(ctlr, rd->dn); put_device(&ctlr->dev); --2.34.1
_______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel