Re: [PATCH 1/3] misc: aspeed: Add Aspeed UART routing control driver.

From: Greg Kroah-Hartman
Date: Thu Dec 10 2020 - 04:43:15 EST

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In reply to: John Wang: "[PATCH 1/3] misc: aspeed: Add Aspeed UART routing control driver."
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On Thu, Dec 10, 2020 at 05:28:53PM +0800, John Wang wrote:
> From: Oskar Senft <osk@xxxxxxxxxx>
>
> This driver adds sysfs files that allow the BMC userspace to configure
> how UARTs and physical serial I/O ports are routed.
>
> Tested: Checked correct behavior (both read & write) on TYAN S7106
> board by manually changing routing settings and confirming that bits
> flow as expected. Tested for UART1 and UART3 as this board doesn't have
> the other UARTs wired up in a testable way.
>
> Signed-off-by: Oskar Senft <osk@xxxxxxxxxx>
> Signed-off-by: Yong Li <yong.b.li@xxxxxxxxxxxxxxx>
> Signed-off-by: Vernon Mauery <vernon.mauery@xxxxxxxxxxxxxxx>
> Signed-off-by: John Wang <wangzhiqiang.bj@xxxxxxxxxxxxx>
> ---
> .../stable/sysfs-driver-aspeed-uart-routing | 14 +
> .../misc-devices/aspeed-uart-routing.txt | 49 +++
> drivers/misc/Kconfig | 6 +
> drivers/misc/Makefile | 1 +
> drivers/misc/aspeed-uart-routing.c | 383 ++++++++++++++++++
> 5 files changed, 453 insertions(+)
> create mode 100644 Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing
> create mode 100644 Documentation/misc-devices/aspeed-uart-routing.txt
> create mode 100644 drivers/misc/aspeed-uart-routing.c
>
> diff --git a/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing
> new file mode 100644
> index 000000000000..5068737d9c12
> --- /dev/null
> +++ b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing
> @@ -0,0 +1,14 @@
> +What: /sys/bus/platform/drivers/aspeed-uart-routing/*/io*
> +Date: August 2018
> +Contact: Oskar Senft <osk@xxxxxxxxxx>
> +Description: Configures the input source for the specific physical
> + serial I/O port.
> +Users: OpenBMC. Proposed changes should be mailed to
> + openbmc@xxxxxxxxxxxxxxxx
> +
> +What: /sys/bus/platform/drivers/aspeed-uart-routing/*/uart*
> +Date: August 2018
> +Contact: Oskar Senft <osk@xxxxxxxxxx>
> +Description: Configures the input source for the specific UART.
> +Users: OpenBMC. Proposed changes should be mailed to
> + openbmc@xxxxxxxxxxxxxxxx
> diff --git a/Documentation/misc-devices/aspeed-uart-routing.txt b/Documentation/misc-devices/aspeed-uart-routing.txt
> new file mode 100644
> index 000000000000..cf1c2a466875
> --- /dev/null
> +++ b/Documentation/misc-devices/aspeed-uart-routing.txt
> @@ -0,0 +1,49 @@
> +Kernel driver aspeed-uart-routing
> +=================================
> +
> +Supported chips:
> +ASPEED AST2500/AST2600
> +
> +Author:
> +Google LLC
> +
> +Description
> +-----------
> +
> +The Aspeed AST2500/AST2600 allows to dynamically route the inputs for the
> +built-in UARTS and physical serial I/O ports.
> +
> +This allows, for example, to connect the output of UART to another UART.
> +This can be used to enable host<->BMC communication via UARTs, e.g. to allow
> +access to the host's serial console.
> +
> +This driver is for the BMC side. The sysfs files allow the BMC userspace
> +which owns the system configuration policy, to configure how UARTs and
> +physical serial I/O ports are routed.
> +
> +The driver provides the following files in sysfs:
> +uart1 Configure the input signal to UART1.
> +uart2 Configure the input signal to UART2.
> +uart3 Configure the input signal to UART3.
> +uart4 Configure the input signal to UART4.
> +uart5 Configure the input signal to UART5.
> +io1 Configure the input signal to physical serial port 1.
> +io2 Configure the input signal to physical serial port 2.
> +io3 Configure the input signal to physical serial port 3.
> +io4 Configure the input signal to physical serial port 4.
> +io5 Configure the input signal to physical serial port 5.
> +
> +When read, each file shows the list of available options with the currently
> +selected option marked by square brackets "[]". The list of available options
> +depends on the selected file.
> +
> +Example:
> +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
> +[io1] io2 io3 io4 uart2 uart3 uart4 io6
> +
> +In this case, UART1 gets its input signal from IO1 (physical serial port 1).
> +
> +$ echo -n "uart3" \
> + >/sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
> +$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
> +io1 io2 io3 io4 uart2 [uart3] uart4 io6

Are you sure there are no other ways to configure this type of thing,
than to a driver-specific sysfs file?

> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index d8626a0d3e31..48a519c59bdf 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -451,6 +451,12 @@ config MCTP_LPC
> Implements the MCTP LPC binding via KCS LPC IO cycles for control and
> LPC FWH cycles for data
>
> +config ASPEED_UART_ROUTING
> + tristate "Aspeed ast2500 UART routing control"
> + help
> + If you want to configure UART routing on Aspeed BMC platforms, enable
> + this option.
> +
> config MISC_RTSX
> tristate
> default MISC_RTSX_PCI || MISC_RTSX_USB
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 183970192ced..4e67e21c2e65 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -60,3 +60,4 @@ obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
> obj-$(CONFIG_NPCM7XX_LPC_BPC) += npcm7xx-lpc-bpc.o
> obj-$(CONFIG_NPCM7XX_PCI_MBOX) += npcm7xx-pci-mbox.o
> obj-$(CONFIG_MCTP_LPC) += mctp-lpc.o
> +obj-$(CONFIG_ASPEED_UART_ROUTING) += aspeed-uart-routing.o
> diff --git a/drivers/misc/aspeed-uart-routing.c b/drivers/misc/aspeed-uart-routing.c
> new file mode 100644
> index 000000000000..21ef5d98c317
> --- /dev/null
> +++ b/drivers/misc/aspeed-uart-routing.c
> @@ -0,0 +1,383 @@
> +/*
> + * UART Routing driver for Aspeed AST2500
> + *
> + * Copyright (c) 2018 Google LLC

No SPDX line?

> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.

Please remove after adding the SPDX line.

> + */
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +
> +/* The Aspeed AST2500 allows to dynamically route the inputs for the built-in
> + * UARTS and physical serial I/O ports.
> + *
> + * This allows, for example, to connect the output of UART to another UART.
> + * This can be used to enable host<->BMC communication via UARTs, e.g. to allow
> + * access to the host's serial console.
> + *
> + * This driver is for the BMC side. The sysfs files allow the BMC userspace
> + * which owns the system configuration policy, to configure how UARTs and
> + * physical serial I/O ports are routed.
> + */
> +
> +#define ASPEED_HICRA_IO1 "io1"
> +#define ASPEED_HICRA_IO2 "io2"
> +#define ASPEED_HICRA_IO3 "io3"
> +#define ASPEED_HICRA_IO4 "io4"
> +#define ASPEED_HICRA_IO5 "io5"
> +#define ASPEED_HICRA_IO6 "io6"
> +#define ASPEED_HICRA_UART1 "uart1"
> +#define ASPEED_HICRA_UART2 "uart2"
> +#define ASPEED_HICRA_UART3 "uart3"
> +#define ASPEED_HICRA_UART4 "uart4"
> +#define ASPEED_HICRA_UART5 "uart5"
> +
> +struct aspeed_uart_routing {
> + struct device *dev;
> + void __iomem *regs;
> + spinlock_t lock;
> +};
> +
> +struct aspeed_uart_routing_selector {
> + struct device_attribute dev_attr;
> + int shift;
> + int mask;
> + const char * const options[];
> +};
> +
> +#define to_routing_selector(_dev_attr) \
> + container_of(_dev_attr, struct aspeed_uart_routing_selector, dev_attr)
> +
> +
> +static ssize_t aspeed_uart_routing_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf);
> +
> +static ssize_t aspeed_uart_routing_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count);
> +
> +#define ROUTING_ATTR(_name) { \
> + .attr = {.name = _name, \
> + .mode = VERIFY_OCTAL_PERMISSIONS(S_IWUSR | S_IRUGO) }, \
> + .show = aspeed_uart_routing_show, \
> + .store = aspeed_uart_routing_store, \
> +}

Why is all of this needed for a driver?

What's wrong with the DEVICE_ATTR_RW()? macro?

> +
> +static struct aspeed_uart_routing_selector uart5_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART5),
> + .shift = 28,
> + .mask = 0xf,
> + .options = {
> + ASPEED_HICRA_IO5, // 0
> + ASPEED_HICRA_IO1, // 1
> + ASPEED_HICRA_IO2, // 2
> + ASPEED_HICRA_IO3, // 3
> + ASPEED_HICRA_IO4, // 4
> + ASPEED_HICRA_UART1, // 5
> + ASPEED_HICRA_UART2, // 6
> + ASPEED_HICRA_UART3, // 7
> + ASPEED_HICRA_UART4, // 8
> + ASPEED_HICRA_IO6, // 9
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector uart4_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART4),
> + .shift = 25,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_IO4, // 0
> + ASPEED_HICRA_IO1, // 1
> + ASPEED_HICRA_IO2, // 2
> + ASPEED_HICRA_IO3, // 3
> + ASPEED_HICRA_UART1, // 4
> + ASPEED_HICRA_UART2, // 5
> + ASPEED_HICRA_UART3, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector uart3_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART3),
> + .shift = 22,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_IO3, // 0
> + ASPEED_HICRA_IO4, // 1
> + ASPEED_HICRA_IO1, // 2
> + ASPEED_HICRA_IO2, // 3
> + ASPEED_HICRA_UART4, // 4
> + ASPEED_HICRA_UART1, // 5
> + ASPEED_HICRA_UART2, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector uart2_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART2),
> + .shift = 19,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_IO2, // 0
> + ASPEED_HICRA_IO3, // 1
> + ASPEED_HICRA_IO4, // 2
> + ASPEED_HICRA_IO1, // 3
> + ASPEED_HICRA_UART3, // 4
> + ASPEED_HICRA_UART4, // 5
> + ASPEED_HICRA_UART1, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector uart1_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART1),
> + .shift = 16,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_IO1, // 0
> + ASPEED_HICRA_IO2, // 1
> + ASPEED_HICRA_IO3, // 2
> + ASPEED_HICRA_IO4, // 3
> + ASPEED_HICRA_UART2, // 4
> + ASPEED_HICRA_UART3, // 5
> + ASPEED_HICRA_UART4, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector io5_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO5),
> + .shift = 12,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_UART5, // 0
> + ASPEED_HICRA_UART1, // 1
> + ASPEED_HICRA_UART2, // 2
> + ASPEED_HICRA_UART3, // 3
> + ASPEED_HICRA_UART4, // 4
> + ASPEED_HICRA_IO1, // 5
> + ASPEED_HICRA_IO3, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector io4_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO4),
> + .shift = 9,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_UART4, // 0
> + ASPEED_HICRA_UART5, // 1
> + ASPEED_HICRA_UART1, // 2
> + ASPEED_HICRA_UART2, // 3
> + ASPEED_HICRA_UART3, // 4
> + ASPEED_HICRA_IO1, // 5
> + ASPEED_HICRA_IO2, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector io3_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO3),
> + .shift = 6,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_UART3, // 0
> + ASPEED_HICRA_UART4, // 1
> + ASPEED_HICRA_UART5, // 2
> + ASPEED_HICRA_UART1, // 3
> + ASPEED_HICRA_UART2, // 4
> + ASPEED_HICRA_IO1, // 5
> + ASPEED_HICRA_IO2, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector io2_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO2),
> + .shift = 3,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_UART2, // 0
> + ASPEED_HICRA_UART3, // 1
> + ASPEED_HICRA_UART4, // 2
> + ASPEED_HICRA_UART5, // 3
> + ASPEED_HICRA_UART1, // 4
> + ASPEED_HICRA_IO3, // 5
> + ASPEED_HICRA_IO4, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +static struct aspeed_uart_routing_selector io1_sel = {
> + .dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO1),
> + .shift = 0,
> + .mask = 0x7,
> + .options = {
> + ASPEED_HICRA_UART1, // 0
> + ASPEED_HICRA_UART2, // 1
> + ASPEED_HICRA_UART3, // 2
> + ASPEED_HICRA_UART4, // 3
> + ASPEED_HICRA_UART5, // 4
> + ASPEED_HICRA_IO3, // 5
> + ASPEED_HICRA_IO4, // 6
> + ASPEED_HICRA_IO6, // 7
> + NULL, // NULL termination
> + },
> +};
> +
> +
> +static struct attribute *aspeed_uart_routing_attrs[] = {
> + &uart1_sel.dev_attr.attr,
> + &uart2_sel.dev_attr.attr,
> + &uart3_sel.dev_attr.attr,
> + &uart4_sel.dev_attr.attr,
> + &uart5_sel.dev_attr.attr,
> + &io1_sel.dev_attr.attr,
> + &io2_sel.dev_attr.attr,
> + &io3_sel.dev_attr.attr,
> + &io4_sel.dev_attr.attr,
> + &io5_sel.dev_attr.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group aspeed_uart_routing_attr_group = {
> + .attrs = aspeed_uart_routing_attrs,
> +};
> +
> +static ssize_t aspeed_uart_routing_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
> + struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
> + int val, pos, len;
> +
> + val = (readl(uart_routing->regs) >> sel->shift) & sel->mask;
> +
> + len = 0;
> + for (pos = 0; sel->options[pos] != NULL; ++pos) {
> + if (pos == val) {
> + len += snprintf(buf + len, PAGE_SIZE - 1 - len,
> + "[%s] ", sel->options[pos]);

Use the sysfs_emit() function please.

> + } else {
> + len += snprintf(buf + len, PAGE_SIZE - 1 - len,
> + "%s ", sel->options[pos]);
> + }
> + }
> +
> + if (val >= pos) {
> + len += snprintf(buf + len, PAGE_SIZE - 1 - len,
> + "[unknown(%d)]", val);
> + }
> +
> + len += snprintf(buf + len, PAGE_SIZE - 1 - len, "\n");
> +
> + return len;
> +}
> +
> +static ssize_t aspeed_uart_routing_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
> + struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
> + int val;
> + u32 reg;
> +
> + val = match_string(sel->options, -1, buf);
> + if (val < 0) {
> + dev_err(dev, "invalid value \"%s\"\n", buf);

So userspace can cause syslog spam? That's not nice :(

> + return -EINVAL;
> + }
> +
> + spin_lock(&uart_routing->lock);
> + reg = readl(uart_routing->regs);
> + // Zero out existing value in specified bits.
> + reg &= ~(sel->mask << sel->shift);
> + // Set new value in specified bits.
> + reg |= (val & sel->mask) << sel->shift;

Don't we have bit manipulation functions?

> + writel(reg, uart_routing->regs);
> + spin_unlock(&uart_routing->lock);
> +
> + return count;
> +}
> +
> +static int aspeed_uart_routing_probe(struct platform_device *pdev)
> +{
> + struct aspeed_uart_routing *uart_routing;
> + struct resource *res;
> + int rc;
> +
> + uart_routing = devm_kzalloc(&pdev->dev,
> + sizeof(*uart_routing),
> + GFP_KERNEL);
> + if (!uart_routing)
> + return -ENOMEM;
> +
> + spin_lock_init(&uart_routing->lock);
> + uart_routing->dev = &pdev->dev;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + uart_routing->regs = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(uart_routing->regs))
> + return PTR_ERR(uart_routing->regs);
> +
> + rc = sysfs_create_group(&uart_routing->dev->kobj,
> + &aspeed_uart_routing_attr_group);

You just raced with userspace and lost :(

Please use the correct api to add a list of sysfs files to a driver.
Huge hint, if you EVER call sysfs_* from a driver, that's usually not a
sign something is correct.

> + if (rc < 0)
> + return rc;
> +
> + platform_set_drvdata(pdev, uart_routing);
> +
> + return 0;
> +}
> +
> +static int aspeed_uart_routing_remove(struct platform_device *pdev)
> +{
> + struct aspeed_uart_routing *uart_routing = platform_get_drvdata(pdev);
> +
> + sysfs_remove_group(&uart_routing->dev->kobj,
> + &aspeed_uart_routing_attr_group);

Again, wrong api :(

> +
> + return 0;
> +}
> +
> +static const struct of_device_id aspeed_uart_routing_table[] = {
> + { .compatible = "aspeed,ast2500-uart-routing" },
> + { },
> +};
> +
> +static struct platform_driver aspeed_uart_routing_driver = {
> + .driver = {
> + .name = "aspeed-uart-routing",
> + .of_match_table = aspeed_uart_routing_table,
> + },
> + .probe = aspeed_uart_routing_probe,
> + .remove = aspeed_uart_routing_remove,
> +};
> +
> +module_platform_driver(aspeed_uart_routing_driver);
> +
> +MODULE_AUTHOR("Oskar Senft <osk@xxxxxxxxxx>");

Who is going to maintain this file?

thanks,

greg k-h

Next message: Viresh Kumar: "[PATCH] arm64: topology: Avoid the static_branch_{enable|disable} dance"
Previous message: Xie He: "Re: [PATCH net-next] net: x25: Fix handling of Restart Request and Restart Confirmation"
In reply to: John Wang: "[PATCH 1/3] misc: aspeed: Add Aspeed UART routing control driver."
Next in thread: John Wang: "Re: [External] Re: [PATCH 1/3] misc: aspeed: Add Aspeed UART routing control driver."
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