[PATCH linux 2/2] drivers/misc: Add Aspeed LPC mbox register driver
Joel Stanley
joel at jms.id.au
Thu Feb 22 15:52:00 AEDT 2018
On Wed, Feb 21, 2018 at 1:55 PM, Cyril Bur <cyrilbur at gmail.com> wrote:
> This provides access to the LPC mbox registers on the ast2400 and
> ast2500 SoCs.
>
> This driver allows arbitrary reads and writes to the 16 mbox data registers
arbitrary sounds scary. Perhaps drop that word?
> on the Aspeed SoC LPC bus. These Aspeed chips are often used in BMC
ASPEED is all caps. I didn't used to, but I'm trying to converge on that.
> systems. This access allows for an inband communication channel with its
> host.
>
> Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
> ---
> drivers/misc/Kconfig | 8 +
> drivers/misc/Makefile | 1 +
> drivers/misc/aspeed-lpc-mbox.c | 343 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 352 insertions(+)
> create mode 100644 drivers/misc/aspeed-lpc-mbox.c
>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 03605f8fc0dc..ea1a723d0db3 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -488,6 +488,14 @@ config ASPEED_LPC_SNOOP
> allows the BMC to listen on and save the data written by
> the host to an arbitrary LPC I/O port.
>
> +config ASPEED_LPC_MBOX
> + tristate "Aspeed ast2400/2500 LPC MBOX Controller"
> + depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
> + help
> + Provides a driver for the LPC attached MBOX registers on Aspeed
> + SoCs (ast2400/2500). This allows for interrupt driven
delete (ast2400/2500)
> + communication between a HOST and BMC.
s/HOST/host/
> +
> config PCI_ENDPOINT_TEST
> depends on PCI
> select CRC32
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index c3c8624f4d95..32b1db960f33 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -54,6 +54,7 @@ obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o
> obj-$(CONFIG_CXL_BASE) += cxl/
> obj-$(CONFIG_ASPEED_LPC_CTRL) += aspeed-lpc-ctrl.o
> obj-$(CONFIG_ASPEED_LPC_SNOOP) += aspeed-lpc-snoop.o
> +obj-$(CONFIG_ASPEED_LPC_MBOX) += aspeed-lpc-mbox.o
> obj-$(CONFIG_PCI_ENDPOINT_TEST) += pci_endpoint_test.o
> obj-$(CONFIG_OCXL) += ocxl/
> obj-$(CONFIG_MISC_RTSX) += cardreader/
> diff --git a/drivers/misc/aspeed-lpc-mbox.c b/drivers/misc/aspeed-lpc-mbox.c
> new file mode 100644
> index 000000000000..c4e468ab3524
> --- /dev/null
> +++ b/drivers/misc/aspeed-lpc-mbox.c
> @@ -0,0 +1,343 @@
> +/*
> + * Copyright 2018 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.
> + */
Cool kids do this one now:
// SPDX-License-Identifier: GPL-2.0+
// Copyright 2018 IBM Corporation
> +
> +#include <linux/interrupt.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/poll.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +#define DEVICE_NAME "aspeed-mbox"
> +
> +#define ASPEED_MBOX_NUM_REGS 16
> +
> +#define ASPEED_MBOX_DATA_0 0x00
> +#define ASPEED_MBOX_STATUS_0 0x40
> +#define ASPEED_MBOX_STATUS_1 0x44
> +#define ASPEED_MBOX_BMC_CTRL 0x48
> +#define ASPEED_MBOX_CTRL_RECV BIT(7)
> +#define ASPEED_MBOX_CTRL_MASK BIT(1)
> +#define ASPEED_MBOX_CTRL_SEND BIT(0)
> +#define ASPEED_MBOX_HOST_CTRL 0x4c
> +#define ASPEED_MBOX_INTERRUPT_0 0x50
> +#define ASPEED_MBOX_INTERRUPT_1 0x54
> +
> +struct aspeed_mbox {
> + struct miscdevice miscdev;
> + struct regmap *regmap;
> + unsigned int base;
> + wait_queue_head_t queue;
> + struct mutex mutex;
> +};
> +
> +static atomic_t aspeed_mbox_open_count = ATOMIC_INIT(0);
> +
> +static u8 aspeed_mbox_inb(struct aspeed_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;
> +}
This is a mess. I'd prefer:
static u8 aspeed_mbox_inb(struct aspeed_mbox *mbox, int reg)
{
int val;
regmap_read(mbox->regmap, mbox->base + reg, &val);
return val;
}
static void aspeed_mbox_outb(struct aspeed_mbox *mbox, u8 data, int reg)
{
regmap_write(mbox->regmap, mbox->base + reg, data);
}
Reads and writes to a mmio address will never fail. Regmap incurs
enough overhead already; we don't need to add more in the driver.
> +
> +static void aspeed_mbox_outb(struct aspeed_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 aspeed_mbox *file_mbox(struct file *file)
> +{
> + return container_of(file->private_data, struct aspeed_mbox, miscdev);
> +}
> +
> +static int aspeed_mbox_open(struct inode *inode, struct file *file)
> +{
> + struct aspeed_mbox *mbox = file_mbox(file);
> +
> + if (atomic_inc_return(&aspeed_mbox_open_count) == 1) {
> + /*
> + * Clear the interrupt status bit if it was left on and unmask
> + * interrupts.
> + * ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step
> + */
> + aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV,
> + ASPEED_MBOX_BMC_CTRL);
> + return 0;
> + }
> +
> + atomic_dec(&aspeed_mbox_open_count);
> + return -EBUSY;
> +}
> +
> +static ssize_t aspeed_mbox_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct aspeed_mbox *mbox = file_mbox(file);
> + char __user *p = buf;
> + ssize_t ret;
> + int i;
> +
> + if (!access_ok(VERIFY_WRITE, buf, count))
> + return -EFAULT;
> +
> + if (count + *ppos > ASPEED_MBOX_NUM_REGS)
> + return -EINVAL;
> +
> + if (file->f_flags & O_NONBLOCK) {
> + if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> + ASPEED_MBOX_CTRL_RECV))
> + return -EAGAIN;
> + } else if (wait_event_interruptible(mbox->queue,
> + aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> + ASPEED_MBOX_CTRL_RECV)) {
> + return -ERESTARTSYS;
> + }
> +
> + mutex_lock(&mbox->mutex);
> +
> + for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
> + uint8_t reg = aspeed_mbox_inb(mbox,
> + ASPEED_MBOX_DATA_0 + (i * 4));
> +
> + ret = __put_user(reg, p);
> + if (ret)
> + goto out_unlock;
> +
> + p++;
> + count--;
> + }
> +
> + /*
> + * ASPEED_MBOX_CTRL_RECV bit is write to clear
> + * also unmasks in 1 step
> + */
> + aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV,
> + ASPEED_MBOX_BMC_CTRL);
> + ret = p - buf;
> +
> +out_unlock:
> + mutex_unlock(&mbox->mutex);
> + return ret;
> +}
> +
> +static ssize_t aspeed_mbox_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct aspeed_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 > ASPEED_MBOX_NUM_REGS)
> + return -EINVAL;
> +
> + mutex_lock(&mbox->mutex);
> +
> + for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
> + ret = __get_user(c, p);
> + if (ret)
> + goto out_unlock;
> +
> + aspeed_mbox_outb(mbox, c, ASPEED_MBOX_DATA_0 + (i * 4));
> + p++;
> + count--;
> + }
> +
> + aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_SEND, ASPEED_MBOX_BMC_CTRL);
> + ret = p - buf;
> +
> +out_unlock:
> + mutex_unlock(&mbox->mutex);
> + return ret;
> +}
> +
> +static unsigned int aspeed_mbox_poll(struct file *file, poll_table *wait)
> +{
> + struct aspeed_mbox *mbox = file_mbox(file);
> + unsigned int mask = 0;
> +
> + poll_wait(file, &mbox->queue, wait);
> +
> + if (aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) & ASPEED_MBOX_CTRL_RECV)
> + mask |= POLLIN;
> +
> + return mask;
> +}
> +
> +static int aspeed_mbox_release(struct inode *inode, struct file *file)
> +{
> + atomic_dec(&aspeed_mbox_open_count);
> + return 0;
> +}
> +
> +static const struct file_operations aspeed_mbox_fops = {
> + .owner = THIS_MODULE,
> + .llseek = no_seek_end_llseek,
> + .read = aspeed_mbox_read,
> + .write = aspeed_mbox_write,
> + .open = aspeed_mbox_open,
> + .release = aspeed_mbox_release,
> + .poll = aspeed_mbox_poll,
> +};
> +
> +static irqreturn_t aspeed_mbox_irq(int irq, void *arg)
> +{
> + struct aspeed_mbox *mbox = arg;
> +
> + if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL)
> + & ASPEED_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 */
> + aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_MASK, ASPEED_MBOX_BMC_CTRL);
> +
> + wake_up(&mbox->queue);
> + return IRQ_HANDLED;
> +}
> +
> +static int aspeed_mbox_config_irq(struct aspeed_mbox *mbox,
> + struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + int rc, irq;
> +
> + irq = irq_of_parse_and_map(dev->of_node, 0);
> + if (!irq)
> + return -ENODEV;
> +
> + rc = devm_request_irq(dev, irq, aspeed_mbox_irq,
> + IRQF_SHARED, DEVICE_NAME, mbox);
> + if (rc < 0) {
> + dev_err(dev, "Unable to request IRQ %d\n", irq);
> + return rc;
> + }
> +
> + /*
> + * Disable all register based interrupts.
> + */
> + aspeed_mbox_outb(mbox, 0x00, ASPEED_MBOX_INTERRUPT_0); /* regs 0 - 7 */
> + aspeed_mbox_outb(mbox, 0x00, ASPEED_MBOX_INTERRUPT_1); /* regs 8 - 15 */
> +
> + /* These registers are write one to clear. Clear them. */
> + aspeed_mbox_outb(mbox, 0xff, ASPEED_MBOX_STATUS_0);
> + aspeed_mbox_outb(mbox, 0xff, ASPEED_MBOX_STATUS_1);
> +
> + aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
> + return 0;
> +}
> +
> +static int aspeed_mbox_probe(struct platform_device *pdev)
> +{
> + struct aspeed_mbox *mbox;
> + struct device *dev;
> + int rc;
> +
> + dev = &pdev->dev;
> +
> + mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
> + if (!mbox)
> + return -ENOMEM;
> +
> + dev_set_drvdata(&pdev->dev, mbox);
> +
> + rc = of_property_read_u32(dev->of_node, "reg", &mbox->base);
> + if (rc) {
> + dev_err(dev, "Couldn't read reg device-tree property\n");
> + return rc;
> + }
> +
> + mbox->regmap = syscon_node_to_regmap(
> + pdev->dev.parent->of_node);
> + if (IS_ERR(mbox->regmap)) {
> + dev_err(dev, "Couldn't get regmap\n");
> + return -ENODEV;
> + }
> +
> + mutex_init(&mbox->mutex);
> + init_waitqueue_head(&mbox->queue);
> +
> + mbox->miscdev.minor = MISC_DYNAMIC_MINOR;
> + mbox->miscdev.name = DEVICE_NAME;
> + mbox->miscdev.fops = &aspeed_mbox_fops;
> + mbox->miscdev.parent = dev;
> + rc = misc_register(&mbox->miscdev);
> + if (rc) {
> + dev_err(dev, "Unable to register device\n");
> + return rc;
> + }
> +
> + rc = aspeed_mbox_config_irq(mbox, pdev);
> + if (rc) {
> + dev_err(dev, "Failed to configure IRQ\n");
> + misc_deregister(&mbox->miscdev);
> + return rc;
> + }
> +
> + return 0;
> +}
> +
> +static int aspeed_mbox_remove(struct platform_device *pdev)
> +{
> + struct aspeed_mbox *mbox = dev_get_drvdata(&pdev->dev);
> +
> + misc_deregister(&mbox->miscdev);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id aspeed_mbox_match[] = {
> + { .compatible = "aspeed,ast2400-mbox" },
> + { .compatible = "aspeed,ast2500-mbox" },
> + { },
> +};
> +
> +static struct platform_driver aspeed_mbox_driver = {
> + .driver = {
> + .name = DEVICE_NAME,
> + .of_match_table = aspeed_mbox_match,
> + },
> + .probe = aspeed_mbox_probe,
> + .remove = aspeed_mbox_remove,
> +};
> +
> +module_platform_driver(aspeed_mbox_driver);
> +
> +MODULE_DEVICE_TABLE(of, aspeed_mbox_match);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Cyril Bur <cyrilbur at gmail.com>");
> +MODULE_DESCRIPTION("Aspeed LPC MBOX reg device driver");
> --
> 2.16.2
>
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