Re: [PATCH v4 04/10] mailbox: sunxi-msgbox: Add a new mailbox driver

Samuel Holland
2019-08-20T13:08:03Z

On 8/20/19 6:18 AM, Ondřej Jirman wrote:
> Hi Samuel,
>
> On Mon, Aug 19, 2019 at 10:23:05PM -0500, Samuel Holland wrote:
>> Allwinner sun8i, sun9i, and sun50i SoCs contain a hardware message box
>> used for communication between the ARM CPUs and the ARISC management
>> coprocessor. The hardware 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 | 10 +
>> drivers/mailbox/Makefile | 2 +
>> drivers/mailbox/sunxi-msgbox.c | 323 +++++++++++++++++++++++++++++++++
>> 3 files changed, 335 insertions(+)
>> create mode 100644 drivers/mailbox/sunxi-msgbox.c
>>
>> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
>> index ab4eb750bbdd..57d12936175e 100644
>> --- a/drivers/mailbox/Kconfig
>> +++ b/drivers/mailbox/Kconfig
>> @@ -227,4 +227,14 @@ 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 SUNXI_MSGBOX
>> + tristate "Allwinner sunxi Message Box"
>> + depends on ARCH_SUNXI || COMPILE_TEST
>> + default ARCH_SUNXI
>> + help
>> + Mailbox implementation for the hardware message box present in
>> + Allwinner sun8i, sun9i, and sun50i SoCs. The hardware message box 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..bec2d50b0976 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_SUNXI_MSGBOX) += sunxi-msgbox.o
>> diff --git a/drivers/mailbox/sunxi-msgbox.c b/drivers/mailbox/sunxi-msgbox.c
>> new file mode 100644
>> index 000000000000..29a5101a5390
>> --- /dev/null
>> +++ b/drivers/mailbox/sunxi-msgbox.c
>> @@ -0,0 +1,323 @@
>> +// 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 sunxi_msgbox {
>> + struct mbox_controller controller;
>> + struct clk *clk;
>> + spinlock_t lock;
>> + void __iomem *regs;
>> +};
>> +
>> +static bool sunxi_msgbox_last_tx_done(struct mbox_chan *chan);
>> +static bool sunxi_msgbox_peek_data(struct mbox_chan *chan);
>> +
>> +static inline int channel_number(struct mbox_chan *chan)
>> +{
>> + return chan - chan->mbox->chans;
>> +}
>> +
>> +static inline struct sunxi_msgbox *channel_to_msgbox(struct mbox_chan *chan)
>> +{
>> + return chan->con_priv;
>> +}
>> +
>> +static irqreturn_t sunxi_msgbox_irq(int irq, void *dev_id)
>> +{
>> + struct sunxi_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 (sunxi_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 sunxi_msgbox_send_data(struct mbox_chan *chan, void *data)
>> +{
>> + struct sunxi_msgbox *mbox = channel_to_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 sunxi_msgbox_startup(struct mbox_chan *chan)
>> +{
>> + struct sunxi_msgbox *mbox = channel_to_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 (sunxi_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 sunxi_msgbox_shutdown(struct mbox_chan *chan)
>> +{
>> + struct sunxi_msgbox *mbox = channel_to_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 (sunxi_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 sunxi_msgbox_last_tx_done(struct mbox_chan *chan)
>> +{
>> + struct sunxi_msgbox *mbox = channel_to_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 sunxi_msgbox_peek_data(struct mbox_chan *chan)
>> +{
>> + struct sunxi_msgbox *mbox = channel_to_msgbox(chan);
>> + int n = channel_number(chan);
>> +
>> + return readl(mbox->regs + MSG_STAT_REG(n)) & MSG_STAT_MASK;
>> +}
>> +
>> +static const struct mbox_chan_ops sunxi_msgbox_chan_ops = {
>> + .send_data = sunxi_msgbox_send_data,
>> + .startup = sunxi_msgbox_startup,
>> + .shutdown = sunxi_msgbox_shutdown,
>> + .last_tx_done = sunxi_msgbox_last_tx_done,
>> + .peek_data = sunxi_msgbox_peek_data,
>> +};
>> +
>> +static int sunxi_msgbox_probe(struct platform_device *pdev)
>> +{
>> + struct device *dev = &pdev->dev;
>> + struct mbox_chan *chans;
>> + struct reset_control *reset;
>> + struct resource *res;
>> + struct sunxi_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;
>> + }
>> +
>> + ret = reset_control_deassert(reset);
>> + if (ret) {
>> + dev_err(dev, "Failed to deassert reset: %d\n", ret);
>> + goto err_disable_unprepare;
>> + }
>
> You need to assert the reset again from now on, in error paths. devm
> will not do that for you.

I know, and that's intentional. This same message box device is used for ATF to
communicate with SCP firmware (on a different channel). This could be happening
on a different core while Linux is running. So Linux is not allowed to deassert
the reset. clk_disable_unprepare() is only okay because the clock is marked as
critical.

>> + 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),
>> + sunxi_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 = &sunxi_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 sunxi_msgbox_remove(struct platform_device *pdev)
>> +{
>> + struct sunxi_msgbox *mbox = platform_get_drvdata(pdev);
>> +
>> + mbox_controller_unregister(&mbox->controller);
>> + clk_disable_unprepare(mbox->clk);
>
> Also, assert the reset here.

Same comment as above. This is intentional.

Thanks,
Samuel

>> + return 0;
>> +}
>> +
>> +static const struct of_device_id sunxi_msgbox_of_match[] = {
>> + { .compatible = "allwinner,sun6i-a31-msgbox", },
>> + {},
>> +};
>> +MODULE_DEVICE_TABLE(of, sunxi_msgbox_of_match);
>> +
>> +static struct platform_driver sunxi_msgbox_driver = {
>> + .driver = {
>> + .name = "sunxi-msgbox",
>> + .of_match_table = sunxi_msgbox_of_match,
>> + },
>> + .probe = sunxi_msgbox_probe,
>> + .remove = sunxi_msgbox_remove,
>> +};
>> +module_platform_driver(sunxi_msgbox_driver);
>> +
>> +MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
>> +MODULE_DESCRIPTION("Allwinner sunxi Message Box");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.21.0