platform/x86/intel/sdsi: Combine read and write mailbox flows

The current mailbox commands are either read-only or write-only and the
flow is different for each. New commands will need to send and receive
data. In preparation for these commands, create a common polling function
to handle sending data and receiving in the same transaction.
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240411025856.2782476-3-david.e.box@linux.intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/intel/sdsi.c

@@ -15,6 +15,7 @@
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/overflow.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
@@ -156,8 +157,8 @@ static int sdsi_status_to_errno(u32 status)
 	}
 }
 
-static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *info,
-			      size_t *data_size)
+static int sdsi_mbox_poll(struct sdsi_priv *priv, struct sdsi_mbox_info *info,
+			  size_t *data_size)
 {
 	struct device *dev = priv->dev;
 	u32 total, loop, eom, status, message_size;
@@ -166,18 +167,10 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *inf
 
 	lockdep_assert_held(&priv->mb_lock);
 
-	/* Format and send the read command */
-	control = FIELD_PREP(CTRL_EOM, 1) |
-		  FIELD_PREP(CTRL_SOM, 1) |
-		  FIELD_PREP(CTRL_RUN_BUSY, 1) |
-		  FIELD_PREP(CTRL_PACKET_SIZE, info->size);
-	writeq(control, priv->control_addr);
-
 	/* For reads, data sizes that are larger than the mailbox size are read in packets. */
 	total = 0;
 	loop = 0;
 	do {
-		void *buf = info->buffer + (SDSI_SIZE_MAILBOX * loop);
 		u32 packet_size;
 
 		/* Poll on ready bit */
@@ -195,6 +188,11 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *inf
 		if (ret)
 			break;
 
+		if (!packet_size) {
+			sdsi_complete_transaction(priv);
+			break;
+		}
+
 		/* Only the last packet can be less than the mailbox size. */
 		if (!eom && packet_size != SDSI_SIZE_MAILBOX) {
 			dev_err(dev, "Invalid packet size\n");
@@ -208,9 +206,13 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *inf
 			break;
 		}
 
-		sdsi_memcpy64_fromio(buf, priv->mbox_addr, round_up(packet_size, SDSI_SIZE_CMD));
+		if (info->buffer) {
+			void *buf = info->buffer + array_size(SDSI_SIZE_MAILBOX, loop);
 
-		total += packet_size;
+			sdsi_memcpy64_fromio(buf, priv->mbox_addr,
+					     round_up(packet_size, SDSI_SIZE_CMD));
+			total += packet_size;
+		}
 
 		sdsi_complete_transaction(priv);
 	} while (!eom && ++loop < MBOX_MAX_PACKETS);
@@ -230,16 +232,33 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *inf
 		dev_warn(dev, "Read count %u differs from expected count %u\n",
 			 total, message_size);
 
-	*data_size = total;
+	if (data_size)
+		*data_size = total;
 
 	return 0;
 }
 
-static int sdsi_mbox_cmd_write(struct sdsi_priv *priv, struct sdsi_mbox_info *info)
+static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info *info,
+			      size_t *data_size)
+{
+	u64 control;
+
+	lockdep_assert_held(&priv->mb_lock);
+
+	/* Format and send the read command */
+	control = FIELD_PREP(CTRL_EOM, 1) |
+		  FIELD_PREP(CTRL_SOM, 1) |
+		  FIELD_PREP(CTRL_RUN_BUSY, 1) |
+		  FIELD_PREP(CTRL_PACKET_SIZE, info->size);
+	writeq(control, priv->control_addr);
+
+	return sdsi_mbox_poll(priv, info, data_size);
+}
+
+static int sdsi_mbox_cmd_write(struct sdsi_priv *priv, struct sdsi_mbox_info *info,
+			       size_t *data_size)
 {
 	u64 control;
-	u32 status;
-	int ret;
 
 	lockdep_assert_held(&priv->mb_lock);
 
@@ -256,20 +275,7 @@ static int sdsi_mbox_cmd_write(struct sdsi_priv *priv, struct sdsi_mbox_info *in
 		  FIELD_PREP(CTRL_PACKET_SIZE, info->size);
 	writeq(control, priv->control_addr);
 
-	/* Poll on ready bit */
-	ret = readq_poll_timeout(priv->control_addr, control, control & CTRL_READY,
-				 MBOX_POLLING_PERIOD_US, MBOX_TIMEOUT_US);
-
-	if (ret)
-		goto release_mbox;
-
-	status = FIELD_GET(CTRL_STATUS, control);
-	ret = sdsi_status_to_errno(status);
-
-release_mbox:
-	sdsi_complete_transaction(priv);
-
-	return ret;
+	return sdsi_mbox_poll(priv, info, data_size);
 }
 
 static int sdsi_mbox_acquire(struct sdsi_priv *priv, struct sdsi_mbox_info *info)
@@ -313,7 +319,8 @@ static int sdsi_mbox_acquire(struct sdsi_priv *priv, struct sdsi_mbox_info *info
 	return ret;
 }
 
-static int sdsi_mbox_write(struct sdsi_priv *priv, struct sdsi_mbox_info *info)
+static int sdsi_mbox_write(struct sdsi_priv *priv, struct sdsi_mbox_info *info,
+			   size_t *data_size)
 {
 	int ret;
 
@@ -323,7 +330,7 @@ static int sdsi_mbox_write(struct sdsi_priv *priv, struct sdsi_mbox_info *info)
 	if (ret)
 		return ret;
 
-	return sdsi_mbox_cmd_write(priv, info);
+	return sdsi_mbox_cmd_write(priv, info, data_size);
 }
 
 static int sdsi_mbox_read(struct sdsi_priv *priv, struct sdsi_mbox_info *info, size_t *data_size)
@@ -342,7 +349,7 @@ static int sdsi_mbox_read(struct sdsi_priv *priv, struct sdsi_mbox_info *info, s
 static ssize_t sdsi_provision(struct sdsi_priv *priv, char *buf, size_t count,
 			      enum sdsi_command command)
 {
-	struct sdsi_mbox_info info;
+	struct sdsi_mbox_info info = {};
 	int ret;
 
 	if (count > (SDSI_SIZE_WRITE_MSG - SDSI_SIZE_CMD))
@@ -364,7 +371,9 @@ static ssize_t sdsi_provision(struct sdsi_priv *priv, char *buf, size_t count,
 	ret = mutex_lock_interruptible(&priv->mb_lock);
 	if (ret)
 		goto free_payload;
-	ret = sdsi_mbox_write(priv, &info);
+
+	ret = sdsi_mbox_write(priv, &info, NULL);
+
 	mutex_unlock(&priv->mb_lock);
 
 free_payload:
@@ -408,7 +417,7 @@ static ssize_t
 certificate_read(u64 command, struct sdsi_priv *priv, char *buf, loff_t off,
 		 size_t count)
 {
-	struct sdsi_mbox_info info;
+	struct sdsi_mbox_info info = {};
 	size_t size;
 	int ret;