[PATCH 2/4] platform/x86/amd/pmc: Fix error handling in amd_stb_s2d_init()

[Mario Limonciello]

amd_stb_s2d_init() has two problems on its error paths:

 - The return value of the S2D_TELEMETRY_SIZE SMU command is discarded.
   When the SMU refuses the command (e.g. "SMU cmd failed. err: 0xff")
   the failure is only noticed indirectly through the telemetry size
   check and reported as -EIO, masking the real error.

 - dev->msg_port is switched to MSG_PORT_S2D before issuing the S2D SMU
   commands but is only restored to MSG_PORT_PMC on the success path.
   The early "return -EIO" leaves the port stuck on MSG_PORT_S2D, so all
   subsequent SMU communication - including the s2idle prepare/restore
   handlers - is directed at the wrong mailbox.

Consolidate the exit path through a single label so the message port is
always restored, and propagate the SMU command error directly instead of
inferring it from the size.

Assisted-by: Claude:opus
Reported-by: Francis De Brabandere <francisdb@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221759
Tested-by: Francis De Brabandere <francisdb@xxxxxxxxx>
Fixes: 3d7d407dfb05 ("platform/x86: amd-pmc: Add support for AMD Spill to DRAM STB feature")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 drivers/platform/x86/amd/pmc/mp1_stb.c | 28 +++++++++++++++-----------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/platform/x86/amd/pmc/mp1_stb.c b/drivers/platform/x86/amd/pmc/mp1_stb.c
index 753d630f3283d..6a048cb2605ec 100644
--- a/drivers/platform/x86/amd/pmc/mp1_stb.c
+++ b/drivers/platform/x86/amd/pmc/mp1_stb.c
@@ -289,7 +289,7 @@ int amd_stb_s2d_init(struct amd_pmc_dev *dev)
 	u32 phys_addr_low, phys_addr_hi;
 	u64 stb_phys_addr;
 	u32 size = 0;
-	int ret;
+	int ret = 0;
 
 	if (!enable_stb)
 		return 0;
@@ -306,13 +306,17 @@ int amd_stb_s2d_init(struct amd_pmc_dev *dev)
 	/* Spill to DRAM feature uses separate SMU message port */
 	dev->msg_port = MSG_PORT_S2D;
 
-	amd_pmc_send_cmd(dev, S2D_TELEMETRY_SIZE, &size, dev->stb_arg.s2d_msg_id, true);
-	if (size != S2D_TELEMETRY_BYTES_MAX)
-		return -EIO;
+	ret = amd_pmc_send_cmd(dev, S2D_TELEMETRY_SIZE, &size, dev->stb_arg.s2d_msg_id, true);
+	if (ret)
+		goto out;
+	if (size != S2D_TELEMETRY_BYTES_MAX) {
+		ret = -EIO;
+		goto out;
+	}
 
-	/* Get DRAM size */
-	ret = amd_pmc_send_cmd(dev, S2D_DRAM_SIZE, &dev->dram_size, dev->stb_arg.s2d_msg_id, true);
-	if (ret || !dev->dram_size)
+	/* Get DRAM size; fall back to the default if the query fails */
+	if (amd_pmc_send_cmd(dev, S2D_DRAM_SIZE, &dev->dram_size, dev->stb_arg.s2d_msg_id, true) ||
+	    !dev->dram_size)
 		dev->dram_size = S2D_TELEMETRY_DRAMBYTES_MAX;
 
 	/* Get STB DRAM address */
@@ -321,12 +325,12 @@ int amd_stb_s2d_init(struct amd_pmc_dev *dev)
 
 	stb_phys_addr = ((u64)phys_addr_hi << 32 | phys_addr_low);
 
-	/* Clear msg_port for other SMU operation */
-	dev->msg_port = MSG_PORT_PMC;
-
 	dev->stb_virt_addr = devm_ioremap(dev->dev, stb_phys_addr, dev->dram_size);
 	if (!dev->stb_virt_addr)
-		return -ENOMEM;
+		ret = -ENOMEM;
 
-	return 0;
+out:
+	/* Restore the default message port for subsequent SMU operations */
+	dev->msg_port = MSG_PORT_PMC;
+	return ret;
 }
-- 
2.43.0