platform/x86/amd: pmc: Add num_samples message id support to STB

Recent PMFWs have the support for S2D_NUM_SAMPLES message ID that
can tell the current number of samples present within the STB DRAM.

num_samples returned would let the driver know the start of the read
from the last push location. This way, the driver would emit the
top most region of the STB DRAM.

Co-developed-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20230206150855.1938810-2-Shyam-sundar.S-k@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/amd/pmc.c

@@ -114,6 +114,7 @@ enum s2d_arg {
 	S2D_TELEMETRY_SIZE = 0x01,
 	S2D_PHYS_ADDR_LOW,
 	S2D_PHYS_ADDR_HIGH,
+	S2D_NUM_SAMPLES,
 };
 
 struct amd_pmc_bit_map {
@@ -246,13 +247,35 @@ static const struct file_operations amd_pmc_stb_debugfs_fops = {
 static int amd_pmc_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
 {
 	struct amd_pmc_dev *dev = filp->f_inode->i_private;
-	u32 *buf;
+	u32 *buf, fsize, num_samples, stb_rdptr_offset = 0;
+	int ret;
 
 	buf = kzalloc(S2D_TELEMETRY_BYTES_MAX, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 
-	memcpy_fromio(buf, dev->stb_virt_addr, S2D_TELEMETRY_BYTES_MAX);
+	/* Spill to DRAM num_samples uses separate SMU message port */
+	dev->msg_port = 1;
+
+	/* Get the num_samples to calculate the last push location */
+	ret = amd_pmc_send_cmd(dev, S2D_NUM_SAMPLES, &num_samples, STB_SPILL_TO_DRAM, 1);
+	/* Clear msg_port for other SMU operation */
+	dev->msg_port = 0;
+	if (ret) {
+		dev_err(dev->dev, "error: S2D_NUM_SAMPLES not supported : %d\n", ret);
+		return ret;
+	}
+
+	/* Start capturing data from the last push location */
+	if (num_samples > S2D_TELEMETRY_BYTES_MAX) {
+		fsize  = S2D_TELEMETRY_BYTES_MAX;
+		stb_rdptr_offset = num_samples - fsize;
+	} else {
+		fsize = num_samples;
+		stb_rdptr_offset = 0;
+	}
+
+	memcpy_fromio(buf, dev->stb_virt_addr + stb_rdptr_offset, fsize);
 	filp->private_data = buf;
 
 	return 0;