[PATCH 3/4] platform/x86/amd/hsmp: Expose socket attributes from the platform driver

[Erwan Velu <erwanaliasr1@gmail.com>]

From: Erwan Velu <e.velu@criteo.com>

The platform driver only exposes metrics_bin, so on systems without the
HSMP ACPI object, attributes such as pwr_current_active_freq_limit are
missing although the driver can send the same HSMP messages as the ACPI
one.

Register the /sys/devices/amd_hsmp/socketN devices from the platform
driver too, so both drivers expose the same attributes at the same
location. The legacy amd_hsmp/socketN/metrics_bin files are kept.

The devices are torn down by a devres action added after
hsmp_pltdrv_release(), so they are gone before the socket array they
reference is released, and they are registered before /dev/hsmp so a
probe failure leaves nothing behind.

Assisted-by: claude-opus-5-5
Signed-off-by: Erwan Velu <e.velu@criteo.com>
---
 Documentation/arch/x86/amd_hsmp.rst  | 16 ++++++++++------
 drivers/platform/x86/amd/hsmp/plat.c | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/Documentation/arch/x86/amd_hsmp.rst b/Documentation/arch/x86/amd_hsmp.rst
index aba4a009bd8d..954e938eea3d 100644
--- a/Documentation/arch/x86/amd_hsmp.rst
+++ b/Documentation/arch/x86/amd_hsmp.rst
@@ -57,11 +57,16 @@ In-kernel integration:
 HSMP sysfs interface
 ====================
 
-The ACPI driver exposes its per socket sysfs files in a per socket
-directory created at /sys/devices/amd_hsmp/socket%d/.
+Both the ACPI and plat drivers expose the same set of per socket sysfs
+files in a per socket directory created at /sys/devices/amd_hsmp/socket%d/.
 
-For backward compatibility, the files are also available under
-/sys/devices/platform/AMDI0097:0X/.
+For backward compatibility, the files are also available at their
+historical locations:
+
+* ACPI driver: all the files of this section under
+  /sys/devices/platform/AMDI0097:0X/.
+* plat driver: metrics_bin only, under
+  /sys/devices/platform/amd_hsmp/socket%d/.
 
 1. Metrics table binary sysfs
 
@@ -69,8 +74,7 @@ AMD MI300A MCM provides GET_METRICS_TABLE message to retrieve
 most of the system management information from SMU in one go.
 
 The metrics table is made available as hexadecimal sysfs binary file
-under per socket sysfs directory created at
-/sys/devices/platform/amd_hsmp/socket%d/metrics_bin
+/sys/devices/amd_hsmp/socket%d/metrics_bin
 
 Note: lseek() is not supported as entire metrics table is read.
 
diff --git a/drivers/platform/x86/amd/hsmp/plat.c b/drivers/platform/x86/amd/hsmp/plat.c
index e9b2b809c0f5..03317f342c69 100644
--- a/drivers/platform/x86/amd/hsmp/plat.c
+++ b/drivers/platform/x86/amd/hsmp/plat.c
@@ -222,9 +222,18 @@ static void hsmp_pltdrv_release(void *data)
 	hsmp_pdev->sock = NULL;
 }
 
+static void hsmp_pltdrv_sock_devs_release(void *data)
+{
+	u16 i;
+
+	for (i = 0; i < hsmp_pdev->num_sockets; i++)
+		hsmp_sock_dev_unregister(&hsmp_pdev->sock[i]);
+}
+
 static int hsmp_pltdrv_probe(struct platform_device *pdev)
 {
 	int ret;
+	u16 i;
 
 	hsmp_pdev->sock = devm_kcalloc(&pdev->dev, hsmp_pdev->num_sockets,
 				       sizeof(*hsmp_pdev->sock),
@@ -253,6 +262,17 @@ static int hsmp_pltdrv_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = devm_add_action_or_reset(&pdev->dev, hsmp_pltdrv_sock_devs_release, NULL);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < hsmp_pdev->num_sockets; i++) {
+		ret = hsmp_sock_dev_register(&hsmp_pdev->sock[i]);
+		if (ret)
+			dev_warn(&pdev->dev, "Failed to register HSMP socket%u device: %d\n",
+				 i, ret);
+	}
+
 	ret = hsmp_misc_register(&pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register misc device\n");
-- 
2.53.0