LPC/MBOX work

Documentation/devicetree/bindings/misc/aspeed-lpc-ctrl.txt new file +3 -0

+the LPC bus can be access by other processors on the system, address
+ranges on the bus can map accesses from another processor to regions
+of the ASpeed SoC memory space.

index 7c78eb1c01ff..c84e833c9480 100644

arch/arm/boot/dts/aspeed-g4.dtsi +2 -0

 
+                       lpc_host: lpc-host@80 {
+                               compatible = "aspeed,ast2400-lpc-host", "simple-mfd", "syscon";

arch/arm/boot/dts/aspeed-g4.dtsi +4 -0

+                                       flash = <&host_pnor>;
+                                       reg = <0x0 0x80>;
+                               };
+

This provides access to the mbox registers on the ast2400 and ast2500 boards.

This driver allows arbitrary reads and writes to the 16 data registers as the other end may have configured the mbox hardware to provide an interrupt when a specific register gets written to.

Signed-off-by Cyril Bur <[email protected]>

---
 drivers/mailbox/Kconfig       |   9 ++
 drivers/mailbox/Makefile      |   3 +
 drivers/mailbox/aspeed-mbox.c | 365 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 377 insertions(+)
 create mode 100644 drivers/mailbox/aspeed-mbox.c

drivers/mailbox/Kconfig +9 -0

index 5305923752d2..b9aebe139b9c 100644
@@ -123,4 +123,13 @@ config XGENE_SLIMPRO_MBOX
          It is used to send short messages between ARM64-bit cores and
          the SLIMpro Management Engine, primarily for PM. Say Y here if you
          want to use the APM X-Gene SLIMpro IPCM support.
+
+config ASPEED_MBOX
+       depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
+       bool "Aspeed ast2400/2500 Mailbox Controller"
+       default "y"
+       ---help---
+         Provides a driver for the MBOX registers found on Aspeed SOCs
+         (AST2400 and AST2500). This driver provides a device for aspeed
+         mbox registers
 endif

drivers/mailbox/Makefile +3 -0

index 0be3e742bb7d..99d17f3b9552 100644
@@ -25,3 +25,6 @@ obj-$(CONFIG_TI_MESSAGE_MANAGER) += ti-msgmgr.o
 obj-$(CONFIG_XGENE_SLIMPRO_MBOX) += mailbox-xgene-slimpro.o
 
 obj-$(CONFIG_HI6220_MBOX)      += hi6220-mailbox.o
+
+obj-$(CONFIG_ASPEED_MBOX)              += aspeed-mbox.o
+

drivers/mailbox/aspeed-mbox.c new file +36 -0

new file mode 100644
index 000000000000..6820f73085db
@@ -0,0 +1,365 @@
+/*
+ * Copyright 2016 IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/regmap.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+
+#define DEVICE_NAME    "aspeed-mbox"
+
+#define MBOX_NUM_REGS 16
+
+#define MBOX_DATA_0 0x00
+#define MBOX_STATUS_0 0x40

drivers/mailbox/aspeed-mbox.c new file +70 -0

+       struct miscdevice       miscdev;
+       struct regmap           *regmap;
+       unsigned int            base;
+       int                     irq;
+       wait_queue_head_t       queue;
+       struct timer_list       poll_timer;
+       struct mutex            mutex;
+};
+
+static atomic_t mbox_open_count = ATOMIC_INIT(0);
+
+static u8 mbox_inb(struct mbox *mbox, int reg)
+{
+       /*
+        * The mbox registers are actually only one byte but are addressed
+        * four bytes apart. The other three bytes are marked 'reserved',
+        * they *should* be zero but lets not rely on it.
+        * I am going to rely on the fact we can casually read/write to them...
+        */
+       unsigned int val = 0xff; /* If regmap throws an error return 0xff */
+       int rc = regmap_read(mbox->regmap, mbox->base + reg, &val);
+
+       if (rc)
+               dev_err(mbox->miscdev.parent, "regmap_read() failed with "
+                               "%d (reg: 0x%08x)\n", rc, reg);
+
+       return val & 0xff;
+}
+
+static void mbox_outb(struct mbox *mbox, u8 data, int reg)
+{
+       int rc = regmap_write(mbox->regmap, mbox->base + reg, data);
+
+       if (rc)
+               dev_err(mbox->miscdev.parent, "regmap_write() failed with "
+                               "%d (data: %u reg: 0x%08x)\n", rc, data, reg);
+}
+
+static struct mbox *file_mbox(struct file *file)
+{
+       return container_of(file->private_data, struct mbox, miscdev);
+}
+
+static int mbox_open(struct inode *inode, struct file *file)
+{
+       struct mbox *mbox = file_mbox(file);
+
+       if (atomic_inc_return(&mbox_open_count) == 1) {
+               /*
+                * Clear the interrupt status bit if it was left on and unmask
+                * interrupts.
+                * MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step
+                */
+               mbox_outb(mbox, MBOX_CTRL_RECV, MBOX_BMC_CTRL);
+               return 0;
+       }
+
+       atomic_dec(&mbox_open_count);
+       return -EBUSY;
+}
+
+static ssize_t mbox_read(struct file *file, char __user *buf,
+                               size_t count, loff_t *ppos)
+{
+       struct mbox *mbox = file_mbox(file);
+       char __user *p = buf;
+       ssize_t ret;
+       int i;
+
+       if (!access_ok(VERIFY_WRITE, buf, count))

drivers/mailbox/aspeed-mbox.c new file +122 -0

+                       ret = -EFAULT;
+                       goto out_unlock;
+               }
+       }
+
+       /* MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step */
+       mbox_outb(mbox, MBOX_CTRL_RECV, MBOX_BMC_CTRL);
+       ret = p - buf;
+
+out_unlock:
+       mutex_unlock(&mbox->mutex);
+       return ret;
+}
+
+static ssize_t mbox_write(struct file *file, const char __user *buf,
+                               size_t count, loff_t *ppos)
+{
+       struct mbox *mbox = file_mbox(file);
+       const char __user *p = buf;
+       ssize_t ret;
+       char c;
+       int i;
+
+       if (!access_ok(VERIFY_READ, buf, count))
+               return -EFAULT;
+
+       if (count + *ppos > MBOX_NUM_REGS)
+               return -EINVAL;
+
+       mutex_lock(&mbox->mutex);
+
+       for (i = *ppos; count > 0 && i < MBOX_NUM_REGS; i++) {
+               if (__get_user(c, p)) {
+                       ret = -EFAULT;
+                       goto out_unlock;
+               }
+
+               mbox_outb(mbox, c, MBOX_DATA_0 + (i * 4));
+               p++;
+               count--;
+       }
+
+       mbox_outb(mbox, MBOX_CTRL_SEND, MBOX_BMC_CTRL);
+       ret = p - buf;
+
+out_unlock:
+       mutex_unlock(&mbox->mutex);
+       return ret;
+}
+
+static unsigned int mbox_poll(struct file *file, poll_table *wait)
+{
+       struct mbox *mbox = file_mbox(file);
+       unsigned int mask = 0;
+
+       poll_wait(file, &mbox->queue, wait);
+
+       if (mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV)
+               mask |= POLLIN;
+
+       return mask;
+}
+
+static int mbox_release(struct inode *inode, struct file *file)
+{
+       atomic_dec(&mbox_open_count);
+       return 0;
+}
+
+static const struct file_operations mbox_fops = {
+       .owner          = THIS_MODULE,
+       .llseek         = no_seek_end_llseek,
+       .read           = mbox_read,
+       .write          = mbox_write,
+       .open           = mbox_open,
+       .release        = mbox_release,
+       .poll           = mbox_poll,
+};
+
+static void poll_timer(unsigned long data)
+{
+       struct mbox *mbox = (void *)data;
+
+       mbox->poll_timer.expires += msecs_to_jiffies(500);
+       wake_up(&mbox->queue);
+       add_timer(&mbox->poll_timer);
+}
+
+static irqreturn_t mbox_irq(int irq, void *arg)
+{
+       struct mbox *mbox = arg;
+
+       if (!(mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV))
+               return IRQ_NONE;
+
+       /*
+        * Leave the status bit set so that we know the data is for us,
+        * clear it once it has been read.
+        */
+
+       /* Mask it off, we'll clear it when we the data gets read */
+       mbox_outb(mbox, MBOX_CTRL_MASK, MBOX_BMC_CTRL);
+
+       wake_up(&mbox->queue);
+       return IRQ_HANDLED;
+}
+
+static int mbox_config_irq(struct mbox *mbox,
+               struct platform_device *pdev)
+{
+       struct device *dev = &pdev->dev;
+       int rc;
+
+       mbox->irq = irq_of_parse_and_map(dev->of_node, 0);
+       if (!mbox->irq)
+               return -ENODEV;
+
+       rc = devm_request_irq(dev, mbox->irq, mbox_irq, IRQF_SHARED,
+                       DEVICE_NAME, mbox);
+       if (rc < 0) {
+               dev_warn(dev, "Unable to request IRQ %d\n", mbox->irq);
+               mbox->irq = 0;

drivers/mailbox/aspeed-mbox.c new file +9 -0

+               setup_timer(&mbox->poll_timer, poll_timer,
+                               (unsigned long)mbox);
+               mbox->poll_timer.expires = jiffies + msecs_to_jiffies(10);
+               add_timer(&mbox->poll_timer);
+       }
+
+out:
+       return rc;
+

drivers/mailbox/aspeed-mbox.c new file +8 -0

+       { },
+};
+
+static struct platform_driver mbox_driver = {
+       .driver = {
+               .name           = DEVICE_NAME,
+               .of_match_table = mbox_match,
+       },

--
2.11.0

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drivers/mailbox/aspeed-mbox.c line 126

Quoted 5 lines

drivers/mailbox/aspeed-mbox.c new file +5 -0

+       if ((file->f_flags & O_NONBLOCK) &&
+               !(mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV))
+                       return -EAGAIN;
+       else if (wait_event_interruptible(mbox->queue,
+                        mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV))

You read MBOX_BMC_CTRL twice. Is that intentional?

Quoted 6 lines · Joel Stanley

Quoted 5 lines

drivers/mailbox/aspeed-mbox.c new file +5 -0

+       if ((file->f_flags & O_NONBLOCK) &&
+               !(mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV))
+                       return -EAGAIN;
+       else if (wait_event_interruptible(mbox->queue,
+                        mbox_inb(mbox, MBOX_BMC_CTRL) & MBOX_CTRL_RECV))

Quoted 1 line

You read MBOX_BMC_CTRL twice. Is that intentional?

In fact, you keep reading it forever thanks to the magic of the wait_event_interruptible macro.

Carry on.

Cheers,

Joel

drivers/mailbox/aspeed-mbox.c new file +11 -0

+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>