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

Ondřej Jirman
2019-08-20T13:34:46Z

Hi,

On Tue, Aug 20, 2019 at 08:07:53AM -0500, Samuel Holland wrote:
> 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.

Okay. It needs to be docummented here though, so that someone will
not "fix" it in the future, after finding this with coccinelle or
something.

regards,
o.

> >> + 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
>
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