Merge tag 'scmi-updates-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into soc/drivers

Arm SCMI updates for v6.4

The main and only new addition this time around is the support for
unidirectional mailbox channels. SCMI communicates between the agent
and the platform using one bidirectional 'a2p' channel used by the agent
to send SCMI commands and synchronously receive the related replies, and
an optional 'p2a' unidirectional channel used to asynchronously receive
delayed responses and notifications emitted from the platform.

In order to support platforms that support only unidirectional mailbox
hardware channels, the existing bindings are extended to support the
same. Both bidirectional and unidirectional channels support for the
SCMI mailbox can coexist. The correct and effective combination of
defined 'mboxes' and 'shmem' descriptors determines the type of the
mailbox channel.

This also contains a fix for the transfers allocation on Rx channel
especially when the base protocol doesn't use Rx channel while some
of the protocols can have dedicated Rx channels.

* tag 'scmi-updates-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
firmware: arm_scmi: Add support for unidirectional mailbox channels
dt-bindings: firmware: arm,scmi: Support mailboxes unidirectional channels
firmware: arm_scmi: Fix xfers allocation on Rx channel
firmware: arm_scmi: Use the bitmap API to allocate bitmaps
firmware: arm_scmi: Fix device node validation for mailbox transport
firmware: arm_scmi: Fix raw coexistence mode behaviour on failure path
firmware: arm_scmi: Remove duplicate include header inclusion
firmware: arm_scmi: Return a literal instead of a variable
firmware: arm_scmi: Clean up a return statement in scmi_probe

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnd Bergmann <[e-mail]>

Documentation/devicetree/bindings/firmware/arm,scmi.yaml

···
     description:
       Specifies the mailboxes used to communicate with SCMI compliant
       firmware.
-    items:
-      - const: tx
-      - const: rx
+    oneOf:
+      - items:
+          - const: tx
+          - const: rx
+        minItems: 1
+      - items:
+          - const: tx
+          - const: tx_reply
+          - const: rx
+        minItems: 2
 
   mboxes:
     description:
       List of phandle and mailbox channel specifiers. It should contain
-      exactly one or two mailboxes, one for transmitting messages("tx")
-      and another optional for receiving the notifications("rx") if supported.
+      exactly one, two or three mailboxes; the first one or two for transmitting
+      messages ("tx") and another optional ("rx") for receiving notifications
+      and delayed responses, if supported by the platform.
+      The number of mailboxes needed for transmitting messages depends on the
+      type of channels exposed by the specific underlying mailbox controller;
+      one single channel descriptor is enough if such channel is bidirectional,
+      while two channel descriptors are needed to represent the SCMI ("tx")
+      channel if the underlying mailbox channels are of unidirectional type.
+      The effective combination in numbers of mboxes and shmem descriptors let
+      the SCMI subsystem determine unambiguosly which type of SCMI channels are
+      made available by the underlying mailbox controller and how to use them.
+       1 mbox / 1 shmem => SCMI TX over 1 mailbox bidirectional channel
+       2 mbox / 2 shmem => SCMI TX and RX over 2 mailbox bidirectional channels
+       2 mbox / 1 shmem => SCMI TX over 2 mailbox unidirectional channels
+       3 mbox / 2 shmem => SCMI TX and RX over 3 mailbox unidirectional channels
+      Any other combination of mboxes and shmem is invalid.
     minItems: 1
-    maxItems: 2
+    maxItems: 3
 
   shmem:
     description:
···
         maxItems: 1
 
       mbox-names:
-        items:
-          - const: tx
-          - const: rx
+        oneOf:
+          - items:
+              - const: tx
+              - const: rx
+            minItems: 1
+          - items:
+              - const: tx
+              - const: tx_reply
+              - const: rx
+            minItems: 2
 
       mboxes:
         minItems: 1
-        maxItems: 2
+        maxItems: 3
 
       shmem:
         minItems: 1

drivers/firmware/arm_scmi/bus.c

···
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/device.h>
-#include <linux/of.h>
 
 #include "common.h"
 
···
 	/* Nothing to do. */
 	if (!phead) {
 		mutex_unlock(&scmi_requested_devices_mtx);
-		return scmi_dev;
+		return NULL;
 	}
 
 	/* Walk the list of requested devices for protocol and create them */

drivers/firmware/arm_scmi/driver.c

···
 	hash_init(info->pending_xfers);
 
 	/* Allocate a bitmask sized to hold MSG_TOKEN_MAX tokens */
-	info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(MSG_TOKEN_MAX),
-					      sizeof(long), GFP_KERNEL);
+	info->xfer_alloc_table = devm_bitmap_zalloc(dev, MSG_TOKEN_MAX,
+						    GFP_KERNEL);
 	if (!info->xfer_alloc_table)
 		return -ENOMEM;
 
···
 		return ret;
 
 	ret = __scmi_xfer_info_init(sinfo, &sinfo->tx_minfo);
-	if (!ret && idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE))
+	if (!ret && !idr_is_empty(&sinfo->rx_idr))
 		ret = __scmi_xfer_info_init(sinfo, &sinfo->rx_minfo);
 
 	return ret;
···
 	struct scmi_handle *handle;
 	const struct scmi_desc *desc;
 	struct scmi_info *info;
+	bool coex = IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX);
 	struct device *dev = &pdev->dev;
 	struct device_node *child, *np = dev->of_node;
 
···
 			dev_warn(dev, "Failed to setup SCMI debugfs.\n");
 
 		if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT)) {
-			bool coex =
-			      IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX);
-
 			ret = scmi_debugfs_raw_mode_setup(info);
 			if (!coex) {
 				if (ret)
 					goto clear_dev_req_notifier;
 
-				/* Bail out anyway when coex enabled */
-				return ret;
+				/* Bail out anyway when coex disabled. */
+				return 0;
 			}
 
 			/* Coex enabled, carry on in any case. */
···
 	ret = scmi_protocol_acquire(handle, SCMI_PROTOCOL_BASE);
 	if (ret) {
 		dev_err(dev, "unable to communicate with SCMI\n");
+		if (coex)
+			return 0;
 		goto notification_exit;
 	}
 

drivers/firmware/arm_scmi/mailbox.c

···
  * struct scmi_mailbox - Structure representing a SCMI mailbox transport
  *
  * @cl: Mailbox Client
- * @chan: Transmit/Receive mailbox channel
+ * @chan: Transmit/Receive mailbox uni/bi-directional channel
+ * @chan_receiver: Optional Receiver mailbox unidirectional channel
  * @cinfo: SCMI channel info
  * @shmem: Transmit/Receive shared memory area
  */
 struct scmi_mailbox {
 	struct mbox_client cl;
 	struct mbox_chan *chan;
+	struct mbox_chan *chan_receiver;
 	struct scmi_chan_info *cinfo;
 	struct scmi_shared_mem __iomem *shmem;
 };
···
 
 static bool mailbox_chan_available(struct device_node *of_node, int idx)
 {
+	int num_mb;
+
+	/*
+	 * Just check if bidirrectional channels are involved, and check the
+	 * index accordingly; proper full validation will be made later
+	 * in mailbox_chan_setup().
+	 */
+	num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
+	if (num_mb == 3 && idx == 1)
+		idx = 2;
+
 	return !of_parse_phandle_with_args(of_node, "mboxes",
 					   "#mbox-cells", idx, NULL);
+}
+
+/**
+ * mailbox_chan_validate  - Validate transport configuration and map channels
+ *
+ * @cdev: Reference to the underlying transport device carrying the
+ *	  of_node descriptor to analyze.
+ * @a2p_rx_chan: A reference to an optional unidirectional channel to use
+ *		 for replies on the a2p channel. Set as zero if not present.
+ * @p2a_chan: A reference to the optional p2a channel.
+ *	      Set as zero if not present.
+ *
+ * At first, validate the transport configuration as described in terms of
+ * 'mboxes' and 'shmem', then determin which mailbox channel indexes are
+ * appropriate to be use in the current configuration.
+ *
+ * Return: 0 on Success or error
+ */
+static int mailbox_chan_validate(struct device *cdev,
+				 int *a2p_rx_chan, int *p2a_chan)
+{
+	int num_mb, num_sh, ret = 0;
+	struct device_node *np = cdev->of_node;
+
+	num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
+	num_sh = of_count_phandle_with_args(np, "shmem", NULL);
+	dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
+
+	/* Bail out if mboxes and shmem descriptors are inconsistent */
+	if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 3 ||
+	    (num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2)) {
+		dev_warn(cdev,
+			 "Invalid channel descriptor for '%s' - mbs:%d  shm:%d\n",
+			 of_node_full_name(np), num_mb, num_sh);
+		return -EINVAL;
+	}
+
+	/* Bail out if provided shmem descriptors do not refer distinct areas  */
+	if (num_sh > 1) {
+		struct device_node *np_tx, *np_rx;
+
+		np_tx = of_parse_phandle(np, "shmem", 0);
+		np_rx = of_parse_phandle(np, "shmem", 1);
+		if (!np_tx || !np_rx || np_tx == np_rx) {
+			dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
+				 of_node_full_name(np));
+			ret = -EINVAL;
+		}
+
+		of_node_put(np_tx);
+		of_node_put(np_rx);
+	}
+
+	/* Calculate channels IDs to use depending on mboxes/shmem layout */
+	if (!ret) {
+		switch (num_mb) {
+		case 1:
+			*a2p_rx_chan = 0;
+			*p2a_chan = 0;
+			break;
+		case 2:
+			if (num_sh == 2) {
+				*a2p_rx_chan = 0;
+				*p2a_chan = 1;
+			} else {
+				*a2p_rx_chan = 1;
+				*p2a_chan = 0;
+			}
+			break;
+		case 3:
+			*a2p_rx_chan = 1;
+			*p2a_chan = 2;
+			break;
+		}
+	}
+
+	return ret;
 }
 
 static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
···
 	struct device *cdev = cinfo->dev;
 	struct scmi_mailbox *smbox;
 	struct device_node *shmem;
-	int ret, idx = tx ? 0 : 1;
+	int ret, a2p_rx_chan, p2a_chan, idx = tx ? 0 : 1;
 	struct mbox_client *cl;
 	resource_size_t size;
 	struct resource res;
+
+	ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan);
+	if (ret)
+		return ret;
+
+	if (!tx && !p2a_chan)
+		return -ENODEV;
 
 	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
 	if (!smbox)
···
 	cl->tx_block = false;
 	cl->knows_txdone = tx;
 
-	smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
+	smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
 	if (IS_ERR(smbox->chan)) {
 		ret = PTR_ERR(smbox->chan);
 		if (ret != -EPROBE_DEFER)
-			dev_err(cdev, "failed to request SCMI %s mailbox\n",
-				tx ? "Tx" : "Rx");
+			dev_err(cdev,
+				"failed to request SCMI %s mailbox\n", desc);
 		return ret;
+	}
+
+	/* Additional unidirectional channel for TX if needed */
+	if (tx && a2p_rx_chan) {
+		smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
+		if (IS_ERR(smbox->chan_receiver)) {
+			ret = PTR_ERR(smbox->chan_receiver);
+			if (ret != -EPROBE_DEFER)
+				dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
+			return ret;
+		}
 	}
 
 	cinfo->transport_info = smbox;
···
 
 	if (smbox && !IS_ERR(smbox->chan)) {
 		mbox_free_channel(smbox->chan);
+		mbox_free_channel(smbox->chan_receiver);
 		cinfo->transport_info = NULL;
 		smbox->chan = NULL;
+		smbox->chan_receiver = NULL;
 		smbox->cinfo = NULL;
 	}