misc: amd-sbi: Add support for CPUID protocol

- AMD provides custom protocol to read Processor feature
capabilities and configuration information through side band.
The information is accessed by providing CPUID Function,
extended function and thread ID to the protocol.
Undefined function returns 0.

Reviewed-by: Naveen Krishna Chatradhi <[e-mail]>
Signed-off-by: Akshay Gupta <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/amd-sbi/rmi-core.c

···
 
 /* Mask for Status Register bit[1] */
 #define SW_ALERT_MASK	0x2
+/* Mask to check H/W Alert status bit */
+#define HW_ALERT_MASK	0x80
 
 /* Software Interrupt for triggering */
 #define START_CMD	0x80
 #define TRIGGER_MAILBOX	0x01
+
+/* Default message lengths as per APML command protocol */
+/* CPUID */
+#define CPUID_RD_DATA_LEN	0x8
+#define CPUID_WR_DATA_LEN	0x8
+#define CPUID_RD_REG_LEN	0xa
+#define CPUID_WR_REG_LEN	0x9
+
+/* CPUID MSR Command Ids */
+#define CPUID_MCA_CMD	0x73
+#define RD_CPUID_CMD	0x91
+
+/* CPUID MCAMSR mask & index */
+#define CPUID_MCA_THRD_MASK	GENMASK(15, 0)
+#define CPUID_MCA_THRD_INDEX	32
+#define CPUID_MCA_FUNC_MASK	GENMASK(31, 0)
+#define CPUID_EXT_FUNC_INDEX	56
+
+/* input for bulk write to CPUID protocol */
+struct cpu_msr_indata {
+	u8 wr_len;	/* const value */
+	u8 rd_len;	/* const value */
+	u8 proto_cmd;	/* const value */
+	u8 thread;	/* thread number */
+	union {
+		u8 reg_offset[4];	/* input value */
+		u32 value;
+	} __packed;
+	u8 ext; /* extended function */
+};
+
+/* output for bulk read from CPUID protocol */
+struct cpu_msr_outdata {
+	u8 num_bytes;	/* number of bytes return */
+	u8 status;	/* Protocol status code */
+	union {
+		u64 value;
+		u8 reg_data[8];
+	} __packed;
+};
+
+static inline void prepare_cpuid_input_message(struct cpu_msr_indata *input,
+					       u8 thread_id, u32 func,
+					       u8 ext_func)
+{
+	input->rd_len		= CPUID_RD_DATA_LEN;
+	input->wr_len		= CPUID_WR_DATA_LEN;
+	input->proto_cmd	= RD_CPUID_CMD;
+	input->thread		= thread_id << 1;
+	input->value		= func;
+	input->ext		= ext_func;
+}
+
+static int sbrmi_get_rev(struct sbrmi_data *data)
+{
+	unsigned int rev;
+	u16 offset = SBRMI_REV;
+	int ret;
+
+	ret = regmap_read(data->regmap, offset, &rev);
+	if (ret < 0)
+		return ret;
+
+	data->rev = rev;
+	return 0;
+}
+
+/* Read CPUID function protocol */
+static int rmi_cpuid_read(struct sbrmi_data *data,
+			  struct apml_cpuid_msg *msg)
+{
+	struct cpu_msr_indata input = {0};
+	struct cpu_msr_outdata output = {0};
+	int val = 0;
+	int ret, hw_status;
+	u16 thread;
+
+	mutex_lock(&data->lock);
+	/* cache the rev value to identify if protocol is supported or not */
+	if (!data->rev) {
+		ret = sbrmi_get_rev(data);
+		if (ret < 0)
+			goto exit_unlock;
+	}
+	/* CPUID protocol for REV 0x10 is not supported*/
+	if (data->rev == 0x10) {
+		ret = -EOPNOTSUPP;
+		goto exit_unlock;
+	}
+
+	thread = msg->cpu_in_out << CPUID_MCA_THRD_INDEX & CPUID_MCA_THRD_MASK;
+
+	/* Thread > 127, Thread128 CS register, 1'b1 needs to be set to 1 */
+	if (thread > 127) {
+		thread -= 128;
+		val = 1;
+	}
+	ret = regmap_write(data->regmap, SBRMI_THREAD128CS, val);
+	if (ret < 0)
+		goto exit_unlock;
+
+	prepare_cpuid_input_message(&input, thread,
+				    msg->cpu_in_out & CPUID_MCA_FUNC_MASK,
+				    msg->cpu_in_out >> CPUID_EXT_FUNC_INDEX);
+
+	ret = regmap_bulk_write(data->regmap, CPUID_MCA_CMD,
+				&input, CPUID_WR_REG_LEN);
+	if (ret < 0)
+		goto exit_unlock;
+
+	/*
+	 * For RMI Rev 0x20, new h/w status bit is introduced. which is used
+	 * by firmware to indicate completion of commands (0x71, 0x72, 0x73).
+	 * wait for the status bit to be set by the hardware before
+	 * reading the data out.
+	 */
+	ret = regmap_read_poll_timeout(data->regmap, SBRMI_STATUS, hw_status,
+				       hw_status & HW_ALERT_MASK, 500, 2000000);
+	if (ret)
+		goto exit_unlock;
+
+	ret = regmap_bulk_read(data->regmap, CPUID_MCA_CMD,
+			       &output, CPUID_RD_REG_LEN);
+	if (ret < 0)
+		goto exit_unlock;
+
+	ret = regmap_write(data->regmap, SBRMI_STATUS,
+			   HW_ALERT_MASK);
+	if (ret < 0)
+		goto exit_unlock;
+
+	if (output.num_bytes != CPUID_RD_REG_LEN - 1) {
+		ret = -EMSGSIZE;
+		goto exit_unlock;
+	}
+	if (output.status) {
+		ret = -EPROTOTYPE;
+		msg->fw_ret_code = output.status;
+		goto exit_unlock;
+	}
+	msg->cpu_in_out = output.value;
+exit_unlock:
+	if (ret < 0)
+		msg->cpu_in_out = 0;
+	mutex_unlock(&data->lock);
+	return ret;
+}
 
 int rmi_mailbox_xfer(struct sbrmi_data *data,
 		     struct apml_mbox_msg *msg)
···
 	return copy_to_user(arg, &msg, sizeof(struct apml_mbox_msg));
 }
 
+static int apml_cpuid_xfer(struct sbrmi_data *data, struct apml_cpuid_msg __user *arg)
+{
+	struct apml_cpuid_msg msg = { 0 };
+	int ret;
+
+	/* Copy the structure from user */
+	if (copy_from_user(&msg, arg, sizeof(struct apml_cpuid_msg)))
+		return -EFAULT;
+
+	/* CPUID Protocol */
+	ret = rmi_cpuid_read(data, &msg);
+	if (ret && ret != -EPROTOTYPE)
+		return ret;
+
+	return copy_to_user(arg, &msg, sizeof(struct apml_cpuid_msg));
+}
+
 static long sbrmi_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
···
 	switch (cmd) {
 	case SBRMI_IOCTL_MBOX_CMD:
 		return apml_mailbox_xfer(data, argp);
+	case SBRMI_IOCTL_CPUID_CMD:
+		return apml_cpuid_xfer(data, argp);
 	default:
 		return -ENOTTY;
 	}

drivers/misc/amd-sbi/rmi-core.h

···
 
 /* SB-RMI registers */
 enum sbrmi_reg {
-	SBRMI_CTRL		= 0x01,
+	SBRMI_REV,
+	SBRMI_CTRL,
 	SBRMI_STATUS,
 	SBRMI_OUTBNDMSG0	= 0x30,
 	SBRMI_OUTBNDMSG1,
···
 	SBRMI_INBNDMSG6,
 	SBRMI_INBNDMSG7,
 	SBRMI_SW_INTERRUPT,
+	SBRMI_THREAD128CS	= 0x4b,
 };
 
 /*
···
 	struct mutex lock;
 	u32 pwr_limit_max;
 	u8 dev_static_addr;
+	u8 rev;
 };
 
 int rmi_mailbox_xfer(struct sbrmi_data *data, struct apml_mbox_msg *msg);

include/uapi/misc/amd-apml.h

···
 	__u32 fw_ret_code;
 };
 
+struct apml_cpuid_msg {
+	/*
+	 * CPUID input
+	 * [0]...[3] cpuid func,
+	 * [4][5] cpuid: thread
+	 * [6] cpuid: ext function & read eax/ebx or ecx/edx
+	 *	[7:0] -> bits [7:4] -> ext function &
+	 *	bit [0] read eax/ebx or ecx/edx
+	 * CPUID output
+	 */
+	__u64 cpu_in_out;
+	/*
+	 * Status code for CPUID read
+	 */
+	__u32 fw_ret_code;
+	__u32 pad;
+};
+
 /*
  * AMD sideband interface base IOCTL
  */
···
  * "-EPROTOTYPE" error is returned to provide additional error details
  */
 #define SBRMI_IOCTL_MBOX_CMD		_IOWR(SB_BASE_IOCTL_NR, 0, struct apml_mbox_msg)
+
+/**
+ * DOC: SBRMI_IOCTL_CPUID_CMD
+ *
+ * @Parameters
+ *
+ * @struct apml_cpuid_msg
+ *	Pointer to the &struct apml_cpuid_msg that will contain the protocol
+ *	information
+ *
+ * @Description
+ * IOCTL command for APML messages using generic _IOWR
+ * The IOCTL provides userspace access to AMD sideband cpuid protocol
+ * - CPUID protocol to get CPU details for Function/Ext Function
+ * at thread level
+ * - returning "-EFAULT" if none of the above
+ * "-EPROTOTYPE" error is returned to provide additional error details
+ */
+#define SBRMI_IOCTL_CPUID_CMD		_IOWR(SB_BASE_IOCTL_NR, 1, struct apml_cpuid_msg)
 
 #endif /*_AMD_APML_H_*/