firmware: scmi: mailbox/smt agent device

This change implements a mailbox transport using SMT format for SCMI
exchanges. This implementation follows the Linux kernel and
SCP-firmware [1] as references implementation for SCMI message
processing using SMT format for communication channel meta-data.

Use of mailboxes in SCMI FDT bindings are defined in the Linux kernel
DT bindings since v4.17.

Links: [1] https://github.com/ARM-software/SCP-firmware
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 139 insertions, 0 deletions

diff --git a/drivers/firmware/scmi/smt.c b/drivers/firmware/scmi/smt.c
new file mode 100644
index 0000000..ce8fe49
--- /dev/null
+++ b/drivers/firmware/scmi/smt.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2015-2019, Arm Limited and Contributors. All rights reserved.
+ * Copyright (C) 2019-2020 Linaro Limited.
+ */
+
+#include <common.h>
+#include <cpu_func.h>
+#include <dm.h>
+#include <errno.h>
+#include <scmi_agent.h>
+#include <asm/cache.h>
+#include <asm/system.h>
+#include <dm/ofnode.h>
+#include <linux/compat.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+
+#include "smt.h"
+
+/**
+ * Get shared memory configuration defined by the referred DT phandle
+ * Return with a errno compliant value.
+ */
+int scmi_dt_get_smt_buffer(struct udevice *dev, struct scmi_smt *smt)
+{
+	int ret;
+	struct ofnode_phandle_args args;
+	struct resource resource;
+	fdt32_t faddr;
+	phys_addr_t paddr;
+
+	ret = dev_read_phandle_with_args(dev, "shmem", NULL, 0, 0, &args);
+	if (ret)
+		return ret;
+
+	ret = ofnode_read_resource(args.node, 0, &resource);
+	if (ret)
+		return ret;
+
+	faddr = cpu_to_fdt32(resource.start);
+	paddr = ofnode_translate_address(args.node, &faddr);
+
+	smt->size = resource_size(&resource);
+	if (smt->size < sizeof(struct scmi_smt_header)) {
+		dev_err(dev, "Shared memory buffer too small\n");
+		return -EINVAL;
+	}
+
+	smt->buf = devm_ioremap(dev, paddr, smt->size);
+	if (!smt->buf)
+		return -ENOMEM;
+
+#ifdef CONFIG_ARM
+	if (dcache_status())
+		mmu_set_region_dcache_behaviour((uintptr_t)smt->buf,
+						smt->size, DCACHE_OFF);
+#endif
+
+	return 0;
+}
+
+/**
+ * Write SCMI message @msg into a SMT shared buffer @smt.
+ * Return 0 on success and with a negative errno in case of error.
+ */
+int scmi_write_msg_to_smt(struct udevice *dev, struct scmi_smt *smt,
+			  struct scmi_msg *msg)
+{
+	struct scmi_smt_header *hdr = (void *)smt->buf;
+
+	if ((!msg->in_msg && msg->in_msg_sz) ||
+	    (!msg->out_msg && msg->out_msg_sz))
+		return -EINVAL;
+
+	if (!(hdr->channel_status & SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE)) {
+		dev_dbg(dev, "Channel busy\n");
+		return -EBUSY;
+	}
+
+	if (smt->size < (sizeof(*hdr) + msg->in_msg_sz) ||
+	    smt->size < (sizeof(*hdr) + msg->out_msg_sz)) {
+		dev_dbg(dev, "Buffer too small\n");
+		return -ETOOSMALL;
+	}
+
+	/* Load message in shared memory */
+	hdr->channel_status &= ~SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE;
+	hdr->length = msg->in_msg_sz + sizeof(hdr->msg_header);
+	hdr->msg_header = SMT_HEADER_TOKEN(0) |
+			  SMT_HEADER_MESSAGE_TYPE(0) |
+			  SMT_HEADER_PROTOCOL_ID(msg->protocol_id) |
+			  SMT_HEADER_MESSAGE_ID(msg->message_id);
+
+	memcpy_toio(hdr->msg_payload, msg->in_msg, msg->in_msg_sz);
+
+	return 0;
+}
+
+/**
+ * Read SCMI message from a SMT shared buffer @smt and copy it into @msg.
+ * Return 0 on success and with a negative errno in case of error.
+ */
+int scmi_read_resp_from_smt(struct udevice *dev, struct scmi_smt *smt,
+			    struct scmi_msg *msg)
+{
+	struct scmi_smt_header *hdr = (void *)smt->buf;
+
+	if (!(hdr->channel_status & SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE)) {
+		dev_err(dev, "Channel unexpectedly busy\n");
+		return -EBUSY;
+	}
+
+	if (hdr->channel_status & SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR) {
+		dev_err(dev, "Channel error reported, reset channel\n");
+		return -ECOMM;
+	}
+
+	if (hdr->length > msg->out_msg_sz + sizeof(hdr->msg_header)) {
+		dev_err(dev, "Buffer to small\n");
+		return -ETOOSMALL;
+	}
+
+	/* Get the data */
+	msg->out_msg_sz = hdr->length - sizeof(hdr->msg_header);
+	memcpy_fromio(msg->out_msg, hdr->msg_payload, msg->out_msg_sz);
+
+	return 0;
+}
+
+/**
+ * Clear SMT flags in shared buffer to allow further message exchange
+ */
+void scmi_clear_smt_channel(struct scmi_smt *smt)
+{
+	struct scmi_smt_header *hdr = (void *)smt->buf;
+
+	hdr->channel_status &= ~SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR;
+}