Date:   Fri, 18 Sep 2020 18:15:15 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-kernel@...r.kernel.org (open list),
        linux-arm-kernel@...ts.infradead.org (moderated list:BROADCOM BCM7XXX
        ARM ARCHITECTURE)
Subject: [PATCH v2 2/2] mailbox: Add Broadcom STB mailbox driver

This is a simple mailbox driver to be used by the SCMI protocol stack.  It
only implements the agent-to-platform channel; we may implement the
platform-to-agent channel in the future.  An unusual aspect of this driver
is how the completion of an SCMI message is indicated.  An SCMI message is
initiated with an ARM SMC call, but the return of this call does not
indicate the execution or completion of the message.  Rather, the message's
completion is signaled by an interrupt.

Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 drivers/mailbox/Kconfig           |  12 +++
 drivers/mailbox/Makefile          |   2 +
 drivers/mailbox/brcmstb-mailbox.c | 173 ++++++++++++++++++++++++++++++
 3 files changed, 187 insertions(+)
 create mode 100644 drivers/mailbox/brcmstb-mailbox.c

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 05b1009e2820..378ebd5a7933 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -254,4 +254,16 @@ config QCOM_IPCC
 	  acts as an interrupt controller for receiving interrupts from clients.
 	  Say Y here if you want to build this driver.
 
+config BRCMSTB_MBOX
+	tristate "Broadcom STB Mailbox"
+	depends on ARM64 || ARM
+	depends on ARM_SCMI_PROTOCOL && ARCH_BRCMSTB
+	default ARM_SCMI_PROTOCOL && ARCH_BRCMSTB
+        help
+          Mailbox implementation of the Broadcom STB for the sole purposes
+          of SCMI communication.  This is used by the SCMI drivers to
+	  communicate with FW that runs in EL3.  This mailbox only implements
+	  the agent-to-platform channgel of SCMI but may be augmented in
+	  the future to add the platform-to-agent channel.
+
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 60d224b723a1..a74efd02eece 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -54,3 +54,5 @@ obj-$(CONFIG_SUN6I_MSGBOX)	+= sun6i-msgbox.o
 obj-$(CONFIG_SPRD_MBOX)		+= sprd-mailbox.o
 
 obj-$(CONFIG_QCOM_IPCC)		+= qcom-ipcc.o
+
+obj-$(CONFIG_BRCMSTB_MBOX)	+= brcmstb-mailbox.o
diff --git a/drivers/mailbox/brcmstb-mailbox.c b/drivers/mailbox/brcmstb-mailbox.c
new file mode 100644
index 000000000000..27d87938b08c
--- /dev/null
+++ b/drivers/mailbox/brcmstb-mailbox.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2017, Broadcom */
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
+#include <linux/arm-smccc.h>
+#endif
+
+#define BRCM_SCMI_SMC_OEM_FUNC	0x400
+#define BRCM_SCMI_MBOX_NUM	0
+#define BRCM_FID(ch) ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+			IS_ENABLED(CONFIG_ARM64), \
+			ARM_SMCCC_OWNER_OEM, \
+			BRCM_SCMI_SMC_OEM_FUNC + (ch))
+enum {
+	A2P_CHAN = 0,
+	NUM_CHAN
+};
+
+struct chan_priv {
+	unsigned int mbox_num;
+	unsigned int ch;
+};
+
+struct brcm_mbox {
+	struct mbox_controller controller;
+	int irqs[NUM_CHAN];
+};
+
+static struct mbox_chan *brcm_mbox_of_xlate(struct mbox_controller *controller,
+					    const struct of_phandle_args *sp)
+{
+	unsigned int ch = sp->args[0];
+	struct brcm_mbox *mbox
+		= container_of(controller, struct brcm_mbox, controller);
+
+	if (!mbox || ch >= NUM_CHAN)
+		return ERR_PTR(-ENOENT);
+
+	return &mbox->controller.chans[ch];
+}
+
+#if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
+static int announce_msg(unsigned int mbox_num, unsigned int ch)
+{
+	struct arm_smccc_res res;
+
+	if (ch >= NUM_CHAN)
+		return -EIO;
+	arm_smccc_smc(BRCM_FID(ch), mbox_num, 0, 0, 0, 0, 0, 0, &res);
+	if (res.a0)
+		return -EIO;
+	return 0;
+}
+#else
+#error Func announce_msg() not defined for the current ARCH
+#endif
+
+static int brcm_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+	struct chan_priv *priv = chan->con_priv;
+
+	return announce_msg(priv->mbox_num, priv->ch);
+}
+
+static int brcm_mbox_startup(struct mbox_chan *chan)
+{
+	return 0;
+}
+
+static const struct mbox_chan_ops brcm_mbox_ops = {
+	.send_data = brcm_mbox_send_data,
+	.startup = brcm_mbox_startup,
+};
+
+static irqreturn_t brcm_a2p_isr(int irq, void *data)
+{
+	struct mbox_chan *chan = data;
+
+	mbox_chan_received_data(chan, NULL);
+	return IRQ_HANDLED;
+}
+
+static int brcm_mbox_probe(struct platform_device *pdev)
+{
+	struct brcm_mbox *mbox;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct chan_priv *chan_priv;
+	int ret;
+
+	if (!np)
+		return -EINVAL;
+
+	mbox = devm_kzalloc(&pdev->dev, sizeof(*mbox), GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+
+	/* Allocate channels */
+	mbox->controller.chans = devm_kzalloc(
+		&pdev->dev, NUM_CHAN * sizeof(struct mbox_chan), GFP_KERNEL);
+	if (!mbox->controller.chans)
+		return -ENOMEM;
+	chan_priv = devm_kzalloc(
+		&pdev->dev, NUM_CHAN * sizeof(struct chan_priv), GFP_KERNEL);
+	if (!chan_priv)
+		return -ENOMEM;
+
+	mbox->irqs[A2P_CHAN] = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(&pdev->dev, mbox->irqs[A2P_CHAN], brcm_a2p_isr,
+				IRQF_NO_SUSPEND, "brcm: SCMI a2p intr",
+				&mbox->controller.chans[A2P_CHAN]);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to setup SCMI a2p isr\n");
+		return ret;
+	}
+	chan_priv[A2P_CHAN].mbox_num = BRCM_SCMI_MBOX_NUM;
+	chan_priv[A2P_CHAN].ch = A2P_CHAN;
+	mbox->controller.chans[A2P_CHAN].con_priv = &chan_priv[A2P_CHAN];
+	mbox->controller.num_chans++;
+	mbox->controller.dev = &pdev->dev;
+	mbox->controller.ops = &brcm_mbox_ops;
+	mbox->controller.of_xlate = brcm_mbox_of_xlate;
+	ret = mbox_controller_register(&mbox->controller);
+	if (ret) {
+		dev_err(dev, "failed to register BrcmSTB mbox\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, mbox);
+	return 0;
+}
+
+static int brcm_mbox_remove(struct platform_device *pdev)
+{
+	struct brcm_mbox *mbox = platform_get_drvdata(pdev);
+
+	mbox_controller_unregister(&mbox->controller);
+
+	return 0;
+}
+
+static const struct of_device_id brcm_mbox_of_match[] = {
+	{ .compatible = "brcm,brcmstb-mbox", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, brcm_mbox_of_match);
+
+static struct platform_driver brcm_mbox_driver = {
+	.probe = brcm_mbox_probe,
+	.remove = brcm_mbox_remove,
+	.driver = {
+		.name = "brcm_mbox",
+		.of_match_table = brcm_mbox_of_match,
+	},
+};
+
+module_platform_driver(brcm_mbox_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Broadcom STB SCMI Mailbox driver");
+MODULE_AUTHOR("Broadcom");
-- 
2.17.1


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