[PATCH v2 7/8] misc: amd-sbi: Add supoort for register xfer

[Akshay Gupta <akshay.gupta@amd.com>]

- Provide user register access over IOCTL.
  Both register read and write are supported.
- APML interface does not provide a syncronysation method. By defining,
  a register access path, we use APML modules and library for
  all APML transactions. Without having to use external tools such as
  i2c-tools, which may cause race conditions.

Signed-off-by: Akshay Gupta <akshay.gupta@amd.com>
Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
---
Changes since v1:
- bifurcated from previous patch 5

 drivers/misc/amd-sbi/rmi-core.c | 22 ++++++++++++++++++++++
 include/uapi/misc/amd-apml.h    |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/drivers/misc/amd-sbi/rmi-core.c b/drivers/misc/amd-sbi/rmi-core.c
index 87bd2ffcbcc1..da223e47d5df 100644
--- a/drivers/misc/amd-sbi/rmi-core.c
+++ b/drivers/misc/amd-sbi/rmi-core.c
@@ -374,6 +374,24 @@ int rmi_mailbox_xfer(struct sbrmi_data *data,
 	return ret;
 }
 
+static int rmi_register_xfer(struct sbrmi_data *data,
+			     struct apml_message *msg)
+{
+	int ret;
+
+	mutex_lock(&data->lock);
+	if (msg->data_in.reg_in[RD_FLAG_INDEX])
+		ret = regmap_read(data->regmap,
+				  msg->data_in.reg_in[REG_OFF_INDEX],
+				  &msg->data_out.mb_out[RD_WR_DATA_INDEX]);
+	else
+		ret = regmap_write(data->regmap,
+				   msg->data_in.reg_in[REG_OFF_INDEX],
+				   msg->data_in.reg_in[REG_VAL_INDEX]);
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
 static long sbrmi_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
 {
 	int __user *arguser = (int  __user *)arg;
@@ -407,6 +425,10 @@ static long sbrmi_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
 		/* MCAMSR protocol */
 		ret = rmi_mca_msr_read(data, &msg);
 		break;
+	case APML_REG:
+		/* REG R/W */
+		ret = rmi_register_xfer(data, &msg);
+		break;
 	default:
 		pr_err("Command:0x%x not recognized\n", msg.cmd);
 		break;
diff --git a/include/uapi/misc/amd-apml.h b/include/uapi/misc/amd-apml.h
index 3d536f2c8815..6d74f4ffba10 100644
--- a/include/uapi/misc/amd-apml.h
+++ b/include/uapi/misc/amd-apml.h
@@ -10,6 +10,7 @@
 enum apml_protocol {
 	APML_CPUID	= 0x1000,
 	APML_MCA_MSR,
+	APML_REG,
 };
 
 /* These are byte indexes into data_in and data_out arrays */
@@ -28,6 +29,7 @@ struct apml_message {
 	 * Mailbox Messages:	0x0 ... 0x999
 	 * APML_CPUID:		0x1000
 	 * APML_MCA_MSR:	0x1001
+	 * APML_REG:		0x1002
 	 */
 	__u32 cmd;
 
@@ -45,6 +47,7 @@ struct apml_message {
 	/*
 	 * [0]...[3] mailbox 32bit input
 	 *	     cpuid & mca msr,
+	 *	     rmi rd/wr: reg_offset
 	 * [4][5] cpuid & mca msr: thread
 	 * [4] rmi reg wr: value
 	 * [6] cpuid: ext function & read eax/ebx or ecx/edx
-- 
2.44.0