[PATCH v5 3/8] mailbox: sun6i-msgbox: Add a new mailbox driver

Samuel Holland
2019-12-15T04:25:23Z

Allwinner sun6i, sun8i, sun9i, and sun50i SoCs contain a hardware
message box used for communication between the ARM CPUs and the ARISC
management coprocessor. This mailbox contains 8 unidirectional
4-message FIFOs.

Add a driver for it, so it can be used for SCPI or other communication
protocols.

Signed-off-by: Samuel Holland <samuel@sholland.org>
---
drivers/mailbox/Kconfig | 9 +
drivers/mailbox/Makefile | 2 +
drivers/mailbox/sun6i-msgbox.c | 332 +++++++++++++++++++++++++++++++++
3 files changed, 343 insertions(+)
create mode 100644 drivers/mailbox/sun6i-msgbox.c

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index ab4eb750bbdd..5a577a6734cf 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -227,4 +227,13 @@ config ZYNQMP_IPI_MBOX
message to the IPI buffer and will access the IPI control
registers to kick the other processor or enquire status.

+config SUN6I_MSGBOX
+ tristate "Allwinner sun6i/sun8i/sun9i/sun50i Message Box"
+ depends on ARCH_SUNXI || COMPILE_TEST
+ default ARCH_SUNXI
+ help
+ Mailbox implementation for the hardware message box present in
+ various Allwinner SoCs. This mailbox is used for communication
+ between the application CPUs and the power management coprocessor.
+
endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index c22fad6f696b..2e4364ef5c47 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -48,3 +48,5 @@ obj-$(CONFIG_STM32_IPCC) += stm32-ipcc.o
obj-$(CONFIG_MTK_CMDQ_MBOX) += mtk-cmdq-mailbox.o

obj-$(CONFIG_ZYNQMP_IPI_MBOX) += zynqmp-ipi-mailbox.o
+
+obj-$(CONFIG_SUN6I_MSGBOX) += sun6i-msgbox.o
diff --git a/drivers/mailbox/sun6i-msgbox.c b/drivers/mailbox/sun6i-msgbox.c
new file mode 100644
index 000000000000..7a41e732457c
--- /dev/null
+++ b/drivers/mailbox/sun6i-msgbox.c
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright (c) 2017-2019 Samuel Holland <samuel@sholland.org>
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+#include <linux/spinlock.h>
+
+#define NUM_CHANS 8
+
+#define CTRL_REG(n) (0x0000 + 0x4 * ((n) / 4))
+#define CTRL_RX(n) BIT(0 + 8 * ((n) % 4))
+#define CTRL_TX(n) BIT(4 + 8 * ((n) % 4))
+
+#define REMOTE_IRQ_EN_REG 0x0040
+#define REMOTE_IRQ_STAT_REG 0x0050
+#define LOCAL_IRQ_EN_REG 0x0060
+#define LOCAL_IRQ_STAT_REG 0x0070
+
+#define RX_IRQ(n) BIT(0 + 2 * (n))
+#define RX_IRQ_MASK 0x5555
+#define TX_IRQ(n) BIT(1 + 2 * (n))
+#define TX_IRQ_MASK 0xaaaa
+
+#define FIFO_STAT_REG(n) (0x0100 + 0x4 * (n))
+#define FIFO_STAT_MASK GENMASK(0, 0)
+
+#define MSG_STAT_REG(n) (0x0140 + 0x4 * (n))
+#define MSG_STAT_MASK GENMASK(2, 0)
+
+#define MSG_DATA_REG(n) (0x0180 + 0x4 * (n))
+
+#define mbox_dbg(mbox, ...) dev_dbg((mbox)->controller.dev, __VA_ARGS__)
+
+struct sun6i_msgbox {
+ struct mbox_controller controller;
+ struct clk *clk;
+ spinlock_t lock;
+ void __iomem *regs;
+};
+
+static bool sun6i_msgbox_last_tx_done(struct mbox_chan *chan);
+static bool sun6i_msgbox_peek_data(struct mbox_chan *chan);
+
+static inline int channel_number(struct mbox_chan *chan)
+{
+ return chan - chan->mbox->chans;
+}
+
+static inline struct sun6i_msgbox *to_sun6i_msgbox(struct mbox_chan *chan)
+{
+ return chan->con_priv;
+}
+
+static irqreturn_t sun6i_msgbox_irq(int irq, void *dev_id)
+{
+ struct sun6i_msgbox *mbox = dev_id;
+ uint32_t status;
+ int n;
+
+ /* Only examine channels that are currently enabled. */
+ status = readl(mbox->regs + LOCAL_IRQ_EN_REG) &
+ readl(mbox->regs + LOCAL_IRQ_STAT_REG);
+
+ if (!(status & RX_IRQ_MASK))
+ return IRQ_NONE;
+
+ for (n = 0; n < NUM_CHANS; ++n) {
+ struct mbox_chan *chan = &mbox->controller.chans[n];
+
+ if (!(status & RX_IRQ(n)))
+ continue;
+
+ while (sun6i_msgbox_peek_data(chan)) {
+ uint32_t msg = readl(mbox->regs + MSG_DATA_REG(n));
+
+ mbox_dbg(mbox, "Channel %d received 0x%08x\n", n, msg);
+ mbox_chan_received_data(chan, &msg);
+ }
+
+ /* The IRQ can be cleared only once the FIFO is empty. */
+ writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int sun6i_msgbox_send_data(struct mbox_chan *chan, void *data)
+{
+ struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+ int n = channel_number(chan);
+ uint32_t msg = *(uint32_t *)data;
+
+ /* Using a channel backwards gets the hardware into a bad state. */
+ if (WARN_ON_ONCE(!(readl(mbox->regs + CTRL_REG(n)) & CTRL_TX(n))))
+ return 0;
+
+ /* We cannot post a new message if the FIFO is full. */
+ if (readl(mbox->regs + FIFO_STAT_REG(n)) & FIFO_STAT_MASK) {
+ mbox_dbg(mbox, "Channel %d busy sending 0x%08x\n", n, msg);
+ return -EBUSY;
+ }
+
+ writel(msg, mbox->regs + MSG_DATA_REG(n));
+ mbox_dbg(mbox, "Channel %d sent 0x%08x\n", n, msg);
+
+ return 0;
+}
+
+static int sun6i_msgbox_startup(struct mbox_chan *chan)
+{
+ struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+ int n = channel_number(chan);
+
+ /* The coprocessor is responsible for setting channel directions. */
+ if (readl(mbox->regs + CTRL_REG(n)) & CTRL_RX(n)) {
+ /* Flush the receive FIFO. */
+ while (sun6i_msgbox_peek_data(chan))
+ readl(mbox->regs + MSG_DATA_REG(n));
+ writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
+
+ /* Enable the receive IRQ. */
+ spin_lock(&mbox->lock);
+ writel(readl(mbox->regs + LOCAL_IRQ_EN_REG) | RX_IRQ(n),
+ mbox->regs + LOCAL_IRQ_EN_REG);
+ spin_unlock(&mbox->lock);
+ }
+
+ mbox_dbg(mbox, "Channel %d startup complete\n", n);
+
+ return 0;
+}
+
+static void sun6i_msgbox_shutdown(struct mbox_chan *chan)
+{
+ struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+ int n = channel_number(chan);
+
+ if (readl(mbox->regs + CTRL_REG(n)) & CTRL_RX(n)) {
+ /* Disable the receive IRQ. */
+ spin_lock(&mbox->lock);
+ writel(readl(mbox->regs + LOCAL_IRQ_EN_REG) & ~RX_IRQ(n),
+ mbox->regs + LOCAL_IRQ_EN_REG);
+ spin_unlock(&mbox->lock);
+
+ /* Attempt to flush the FIFO until the IRQ is cleared. */
+ do {
+ while (sun6i_msgbox_peek_data(chan))
+ readl(mbox->regs + MSG_DATA_REG(n));
+ writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
+ } while (readl(mbox->regs + LOCAL_IRQ_STAT_REG) & RX_IRQ(n));
+ }
+
+ mbox_dbg(mbox, "Channel %d shutdown complete\n", n);
+}
+
+static bool sun6i_msgbox_last_tx_done(struct mbox_chan *chan)
+{
+ struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+ int n = channel_number(chan);
+
+ /*
+ * The hardware allows snooping on the remote user's IRQ statuses.
+ * We consider a message to be acknowledged only once the receive IRQ
+ * for that channel is cleared. Since the receive IRQ for a channel
+ * cannot be cleared until the FIFO for that channel is empty, this
+ * ensures that the message has actually been read. It also gives the
+ * recipient an opportunity to perform minimal processing before
+ * acknowledging the message.
+ */
+ return !(readl(mbox->regs + REMOTE_IRQ_STAT_REG) & RX_IRQ(n));
+}
+
+static bool sun6i_msgbox_peek_data(struct mbox_chan *chan)
+{
+ struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+ int n = channel_number(chan);
+
+ return readl(mbox->regs + MSG_STAT_REG(n)) & MSG_STAT_MASK;
+}
+
+static const struct mbox_chan_ops sun6i_msgbox_chan_ops = {
+ .send_data = sun6i_msgbox_send_data,
+ .startup = sun6i_msgbox_startup,
+ .shutdown = sun6i_msgbox_shutdown,
+ .last_tx_done = sun6i_msgbox_last_tx_done,
+ .peek_data = sun6i_msgbox_peek_data,
+};
+
+static int sun6i_msgbox_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct mbox_chan *chans;
+ struct reset_control *reset;
+ struct resource *res;
+ struct sun6i_msgbox *mbox;
+ int i, ret;
+
+ mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+ if (!mbox)
+ return -ENOMEM;
+
+ chans = devm_kcalloc(dev, NUM_CHANS, sizeof(*chans), GFP_KERNEL);
+ if (!chans)
+ return -ENOMEM;
+
+ for (i = 0; i < NUM_CHANS; ++i)
+ chans[i].con_priv = mbox;
+
+ mbox->clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(mbox->clk)) {
+ ret = PTR_ERR(mbox->clk);
+ dev_err(dev, "Failed to get clock: %d\n", ret);
+ return ret;
+ }
+
+ ret = clk_prepare_enable(mbox->clk);
+ if (ret) {
+ dev_err(dev, "Failed to enable clock: %d\n", ret);
+ return ret;
+ }
+
+ reset = devm_reset_control_get(dev, NULL);
+ if (IS_ERR(reset)) {
+ ret = PTR_ERR(reset);
+ dev_err(dev, "Failed to get reset control: %d\n", ret);
+ goto err_disable_unprepare;
+ }
+
+ /*
+ * NOTE: We rely on platform firmware to preconfigure the channel
+ * directions, and we share this hardware block with other firmware
+ * that runs concurrently with Linux (e.g. a trusted monitor).
+ *
+ * Therefore, we do *not* assert the reset line if probing fails or
+ * when removing the device.
+ */
+ ret = reset_control_deassert(reset);
+ if (ret) {
+ dev_err(dev, "Failed to deassert reset: %d\n", ret);
+ goto err_disable_unprepare;
+ }
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res) {
+ ret = -ENODEV;
+ goto err_disable_unprepare;
+ }
+
+ mbox->regs = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(mbox->regs)) {
+ ret = PTR_ERR(mbox->regs);
+ dev_err(dev, "Failed to map MMIO resource: %d\n", ret);
+ goto err_disable_unprepare;
+ }
+
+ /* Disable all IRQs for this end of the msgbox. */
+ writel(0, mbox->regs + LOCAL_IRQ_EN_REG);
+
+ ret = devm_request_irq(dev, irq_of_parse_and_map(dev->of_node, 0),
+ sun6i_msgbox_irq, 0, dev_name(dev), mbox);
+ if (ret) {
+ dev_err(dev, "Failed to register IRQ handler: %d\n", ret);
+ goto err_disable_unprepare;
+ }
+
+ mbox->controller.dev = dev;
+ mbox->controller.ops = &sun6i_msgbox_chan_ops;
+ mbox->controller.chans = chans;
+ mbox->controller.num_chans = NUM_CHANS;
+ mbox->controller.txdone_irq = false;
+ mbox->controller.txdone_poll = true;
+ mbox->controller.txpoll_period = 5;
+
+ spin_lock_init(&mbox->lock);
+ platform_set_drvdata(pdev, mbox);
+
+ ret = mbox_controller_register(&mbox->controller);
+ if (ret) {
+ dev_err(dev, "Failed to register controller: %d\n", ret);
+ goto err_disable_unprepare;
+ }
+
+ return 0;
+
+err_disable_unprepare:
+ clk_disable_unprepare(mbox->clk);
+
+ return ret;
+}
+
+static int sun6i_msgbox_remove(struct platform_device *pdev)
+{
+ struct sun6i_msgbox *mbox = platform_get_drvdata(pdev);
+
+ mbox_controller_unregister(&mbox->controller);
+ /* See the comment in sun6i_msgbox_probe about the reset line. */
+ clk_disable_unprepare(mbox->clk);
+
+ return 0;
+}
+
+static const struct of_device_id sun6i_msgbox_of_match[] = {
+ { .compatible = "allwinner,sun6i-a31-msgbox", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, sun6i_msgbox_of_match);
+
+static struct platform_driver sun6i_msgbox_driver = {
+ .driver = {
+ .name = "sun6i-msgbox",
+ .of_match_table = sun6i_msgbox_of_match,
+ },
+ .probe = sun6i_msgbox_probe,
+ .remove = sun6i_msgbox_remove,
+};
+module_platform_driver(sun6i_msgbox_driver);
+
+MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
+MODULE_DESCRIPTION("Allwinner sun6i/sun8i/sun9i/sun50i Message Box");
+MODULE_LICENSE("GPL v2");
--
2.23.0