[PATCH 6.18.y] platform/x86/amd/pmc: Fix msg_port restoration in amd_stb_debugfs_open_v2()

[Sasha Levin <sashal@kernel.org>]

From: Mario Limonciello <mario.limonciello@amd.com>

[ Upstream commit cbb32ff92f8a62212e0f7384b1de986ced92082b ]

amd_stb_debugfs_open_v2() switches dev->msg_port to MSG_PORT_S2D to query
S2D telemetry but only restores it to MSG_PORT_PMC on one path.  The early
return on the dump_custom_stb path (and the error/allocation returns) leave
the port stuck on MSG_PORT_S2D, so 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, mirroring the fix in amd_stb_s2d_init().

Reported-by: sashiko.dev
Link: https://sashiko.dev/#/patchset/20260717162023.956346-1-mario.limonciello%40amd.com
Fixes: 2851f4f8ed4e ("platform/x86/amd/pmc: Define enum for S2D/PMC msg_port and add helper function")
Cc: stable@vger.kernel.org
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20260721181756.143084-3-mario.limonciello@amd.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
[ adjusted allocation context to retain kmalloc(struct_size(...), GFP_KERNEL) instead of kmalloc_flex() ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/platform/x86/amd/pmc/mp1_stb.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/x86/amd/pmc/mp1_stb.c b/drivers/platform/x86/amd/pmc/mp1_stb.c
index 1a06425f596de..c2f4e6caf58b6 100644
--- a/drivers/platform/x86/amd/pmc/mp1_stb.c
+++ b/drivers/platform/x86/amd/pmc/mp1_stb.c
@@ -157,7 +157,7 @@ static int amd_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
 	struct amd_pmc_dev *dev = filp->f_inode->i_private;
 	u32 fsize, num_samples, val, stb_rdptr_offset = 0;
 	struct amd_stb_v2_data *stb_data_arr;
-	int ret;
+	int ret = 0;
 
 	/* Write dummy postcode while reading the STB buffer */
 	ret = amd_stb_write(dev, AMD_PMC_STB_DUMMY_PC);
@@ -176,22 +176,24 @@ static int amd_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
 	 * the enhanced dram size. Note that we land here only for the
 	 * platforms that support enhanced dram size reporting.
 	 */
-	if (dump_custom_stb)
-		return amd_stb_handle_efr(filp);
+	if (dump_custom_stb) {
+		ret = amd_stb_handle_efr(filp);
+		goto out;
+	}
 
 	/* Get the num_samples to calculate the last push location */
 	ret = amd_pmc_send_cmd(dev, S2D_NUM_SAMPLES, &num_samples, dev->stb_arg.s2d_msg_id, true);
-	/* Clear msg_port for other SMU operation */
-	dev->msg_port = MSG_PORT_PMC;
 	if (ret) {
 		dev_err(dev->dev, "error: S2D_NUM_SAMPLES not supported : %d\n", ret);
-		return ret;
+		goto out;
 	}
 
 	fsize = min(num_samples, S2D_TELEMETRY_BYTES_MAX);
 	stb_data_arr = kmalloc(struct_size(stb_data_arr, data, fsize), GFP_KERNEL);
-	if (!stb_data_arr)
-		return -ENOMEM;
+	if (!stb_data_arr) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
 	stb_data_arr->size = fsize;
 
@@ -214,7 +216,10 @@ static int amd_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
 
 	filp->private_data = stb_data_arr;
 
-	return 0;
+out:
+	/* Restore the default message port for subsequent SMU operations */
+	dev->msg_port = MSG_PORT_PMC;
+	return ret;
 }
 
 static ssize_t amd_stb_debugfs_read_v2(struct file *filp, char __user *buf, size_t size,
-- 
2.53.0