[PATCH V2] firmware: ti_sci: Scan all device instances when releasing exclusive devices

[Nishanth Menon]

When FIT image with multiple dtbs are involved for R5 boot process,
R5 SPL starts off with the first instance of dtb to probe the
eeprom, then once we have identified the type of board, invocation
of setup_multi_dtb_fit will replace the gd->fdt_blob with the proper
board dtb match. However, when we do this, two things happen:

a) Prior to the invocation of setup_multi_dtb_fit, as part of the eeprom
   discovery process, i2c controller device is already probed and marked
   as exclusive with the match of the very first tisci match (from the
   original boot dtb). This list is stored in the info->dev_list of the
   first probe.
b) When the second dtb is loaded, tisci is probed again (since this is a
   new node) and the new info->dev_list is empty.

At this stage, the exclusive devices such as i2c instances used to
probe the board information is left in the old info->dev_list that is
no longer used actively by the system using the replaced dtb.

As a result of this, the cleanup we intend to do with
ti_sci_cmd_release_exclusive_devices is no longer complete and
leaves the instances such as i2c for eeprom marked used as we scan just
the new info->dev_list.

This creates a problem when Device Manager(DM) firmware starts up later
on in the boot process and identifies that this instance of i2c is
already marked active, so it assumes this can no longer be controlled
by software and is marked internally as reserved and HLOS can no
longer control these instances. This defeated the purpose of
ti_sci_cmd_release_exclusive_devices.

NOTE: This scheme works just fine if the FIT has just a single dtb as
the info->dev_list is upto date.

To fix this, let us make ti_sci_cmd_release_exclusive_devices scan the
all registrations of tisci instances and cleanup all exclusive devices
that have ever been registered.

As part of this, change the prototype of release_exclusive_devices to
drop the handle since that has no further meaning now.

Though this issue was identified on AM64-sk, this can be present in
other builds which use multi-fit-dtb for R5 SPL startup.

Fixes: 9566b777ae0a ("firmware: ti_sci: Add a command for releasing all exclusive devices")
Signed-off-by: Nishanth Menon <nm at ti.com>
---
Changes since V1:
* commit message: s/intent/intend (review comment)
* Added comment to indicate am64x-sk
* No functional changes.

V1: https://lore.kernel.org/r/20250401205515.4078312-1-nm@ti.com

Retaining test log:

Test logs:
==========
prior to this patch:
https://gist.github.com/nmenon/8ce817ac991b6ff898734d15ae5ce623#file-before
With this patch
https://gist.github.com/nmenon/8ce817ac991b6ff898734d15ae5ce623#file-after
Notice that 20000000.i2c is no longer deffered in Linux.

Test of platforms (on c17f03a7e93d  Merge tag 'net-20250314' of https://source.denx.de/u-boot/custodians/u-boot-net)

https://gist.github.com/nmenon/917e15b397e5249dd76664ea62e9e662

Though this was uncovered in automated check in upstream testing, this was also
independently reported in:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1459509/sk-am64b-deferred-probe-of-i2c-bus-using-sdk-09-and-10

 arch/arm/mach-k3/r5/common.c           |  2 +-
 drivers/firmware/ti_sci.c              | 23 ++++++++++++++---------
 include/linux/soc/ti/ti_sci_protocol.h |  2 +-
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/arch/arm/mach-k3/r5/common.c b/arch/arm/mach-k3/r5/common.c
index 0f6c294f1eb2..fd188e7c90e4 100644
--- a/arch/arm/mach-k3/r5/common.c
+++ b/arch/arm/mach-k3/r5/common.c
@@ -144,7 +144,7 @@ void __noreturn jump_to_image_no_args(struct spl_image_info *spl_image)
 	int ret, size = 0, shut_cpu = 0;
 
 	/* Release all the exclusive devices held by SPL before starting ATF */
-	ti_sci->ops.dev_ops.release_exclusive_devices(ti_sci);
+	ti_sci->ops.dev_ops.release_exclusive_devices();
 
 	ret = rproc_init();
 	if (ret)
diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
index 190a1e3f5fc3..54d6689ce783 100644
--- a/drivers/firmware/ti_sci.c
+++ b/drivers/firmware/ti_sci.c
@@ -696,20 +696,25 @@ static int ti_sci_cmd_put_device(const struct ti_sci_handle *handle, u32 id)
 				       MSG_DEVICE_SW_STATE_AUTO_OFF);
 }
 
-static
-int ti_sci_cmd_release_exclusive_devices(const struct ti_sci_handle *handle)
+static int ti_sci_cmd_release_exclusive_devices(void)
 {
 	struct ti_sci_exclusive_dev *dev, *tmp;
 	struct ti_sci_info *info;
 	int i, cnt;
 
-	info = handle_to_ti_sci_info(handle);
-
-	list_for_each_entry_safe(dev, tmp, &info->dev_list, list) {
-		cnt = dev->count;
-		debug("%s: id = %d, cnt = %d\n", __func__, dev->id, cnt);
-		for (i = 0; i < cnt; i++)
-			ti_sci_cmd_put_device(handle, dev->id);
+	/*
+	 * Scan all ti_sci_list registrations, since with FIT images, we could
+	 * have started with one device tree registration and switched over
+	 * to a final version. This prevents exclusive devices identified
+	 * during the first probe to be left orphan.
+	 */
+	list_for_each_entry(info, &ti_sci_list, list) {
+		list_for_each_entry_safe(dev, tmp, &info->dev_list, list) {
+			cnt = dev->count;
+			debug("%s: id = %d, cnt = %d\n", __func__, dev->id, cnt);
+			for (i = 0; i < cnt; i++)
+				ti_sci_cmd_put_device(&info->handle, dev->id);
+		}
 	}
 
 	return 0;
diff --git a/include/linux/soc/ti/ti_sci_protocol.h b/include/linux/soc/ti/ti_sci_protocol.h
index 8e4c43cef311..aa4d105ee988 100644
--- a/include/linux/soc/ti/ti_sci_protocol.h
+++ b/include/linux/soc/ti/ti_sci_protocol.h
@@ -143,7 +143,7 @@ struct ti_sci_dev_ops {
 				 u32 reset_state);
 	int (*get_device_resets)(const struct ti_sci_handle *handle, u32 id,
 				 u32 *reset_state);
-	int (*release_exclusive_devices)(const struct ti_sci_handle *handle);
+	int (*release_exclusive_devices)(void);
 };
 
 /**
-- 
2.47.0