[PATCH] firmware: arm_ffa: Unmap RxTx buffers on device shutdown

[Maxi Saparov <maxi.saparov@gmail.com>]

From: Maxi Saparov <masaparov@coreweave.com>

The SPMC retains the RxTx buffer registration of the current kernel
across kexec. FFA_RXTX_MAP from the kexec'ed kernel is then denied
because the buffers of the previous kernel are still registered, and
the driver fails to probe:

  ARM FF-A: Driver version 1.2
  ARM FF-A: Firmware version 1.1 found
  ARM FF-A: failed to register FFA RxTx buffers

The notification bitmap, when one was created, is retained in the
same way and a later FFA_NOTIFICATION_BITMAP_CREATE is denied.

Add a shutdown callback that releases the notification resources and
unmaps the RxTx buffers. device_shutdown() runs on the kexec path, so
the next kernel finds the SPMC in a clean state and can register its
own buffers. On a regular reboot or power off the extra teardown is
harmless.

Observed on NVIDIA GB200 systems when kexec'ing between kernels with
the FF-A driver active.

Signed-off-by: Maxi Saparov <masaparov@coreweave.com>
---
 drivers/firmware/arm_ffa/driver.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 8654b3365c9b..04948be13b08 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -2222,9 +2222,16 @@ static void ffa_remove(struct platform_device *pdev)
 	drv_info = NULL;
 }
 
+static void ffa_shutdown(struct platform_device *pdev)
+{
+	ffa_notifications_cleanup();
+	ffa_rxtx_unmap();
+}
+
 static struct platform_driver ffa_driver = {
 	.probe = ffa_probe,
 	.remove = ffa_remove,
+	.shutdown = ffa_shutdown,
 	.driver = {
 		.name = FFA_PLATFORM_NAME,
 	},

base-commit: 3b5f4b83c4abc0c9b0a7b9e2b44e816611b7f2ec
-- 
2.55.0