On Tue, 4 Aug 2026 21:14:25 +0200, Miao Wang via B4 Relay
<[email protected]> said:
> From: Miao Wang <[email protected]>
>
> The reset event of BMC is captured through GPIO. However, this driver
> bypasses the GPIO framework and directly accesses the GPIO controller
> through the fixed address. When the same GPIO controller is also
> exposed through ACPI and probed by the corresponding GPIO driver,
> there would be a conflict between the two drivers.
>
> This patch will try to find the GPIO through declared GPIO pin in the
> _CRS resources of the ACPI node. If no such delaration is found, the
> driver will fall back to search for the correct GPIO controller and pin
> according to the fixed address and pin number. A possible DSDT
> declaration for the GPIO pin might be as follows:
>
> Device (BMC0) {
> Name (_ADR, ...) // Match the PCI address of the BMC device
> // \_SB.GPO1 is the ACPI path of the GPIO controller
> Name (_CRS, ResourceTemplate () {
> GpioInt (Edge, ActiveLow, Exclusive, PullNone, 0,
> "\\_SB.GPO1", 0) {
> 14 // 14 is the GPIO pin number
> }
> }
>
> Signed-off-by: Miao Wang <[email protected]>
> ---
> drivers/mfd/ls2k-bmc-core.c | 163
> +++++++++++++++++++++++++++++++-------------
> 1 file changed, 116 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/mfd/ls2k-bmc-core.c b/drivers/mfd/ls2k-bmc-core.c
> index
> e7bebfe696ac4554eb6283279811a27ed865ab73..97a666a136fe41ed4268cb70770201533aebb1d5
> 100644
> --- a/drivers/mfd/ls2k-bmc-core.c
> +++ b/drivers/mfd/ls2k-bmc-core.c
> @@ -26,6 +26,10 @@
> #include <linux/stop_machine.h>
> #include <linux/vt_kern.h>
> #include <linux/console.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/gpio/property.h>
> +#include <linux/gpio/machine.h>
>
> /* LS2K BMC resources */
> #define LS2K_DISPLAY_RES_START (SZ_16M + SZ_2M)
> @@ -81,18 +85,6 @@
>
> #define PCI_REG_STRIDE 0x4
>
> -#define LS2K_BMC_RESET_GPIO 14
> -#define LOONGSON_GPIO_REG_BASE 0x1FE00500
> -#define LOONGSON_GPIO_REG_SIZE 0x18
> -#define LOONGSON_GPIO_OEN 0x0
> -#define LOONGSON_GPIO_FUNC 0x4
> -#define LOONGSON_GPIO_INTPOL 0x10
> -#define LOONGSON_GPIO_INTEN 0x14
> -
> -#define LOONGSON_IO_INT_BASE 16
> -#define LS2K_BMC_RESET_GPIO_INT_VEC (LS2K_BMC_RESET_GPIO % 8)
> -#define LS2K_BMC_RESET_GPIO_GSI (LOONGSON_IO_INT_BASE +
> LS2K_BMC_RESET_GPIO_INT_VEC)
> -
> enum {
> LS2K_BMC_DISPLAY,
> LS2K_BMC_IPMI0,
> @@ -186,6 +178,7 @@ struct ls2k_bmc_ddata {
> struct work_struct bmc_reset_work;
> struct ls2k_bmc_pci_data bmc_pci_data;
> struct ls2k_bmc_bridge_pci_data bridge_pci_data;
> + struct gpio_desc *reset_gpio;
> };
>
> static bool ls2k_bmc_bar0_addr_is_set(struct pci_dev *pdev)
> @@ -375,6 +368,91 @@ static void ls2k_bmc_save_pci_data(struct pci_dev *pdev,
> struct ls2k_bmc_ddata *
> pci_read_config_dword(pdev, PCI_INTERRUPT_LINE,
> &ddata->bmc_pci_data.interrupt_line);
> }
>
> +static struct fwnode_handle *gpio_dev_get_fwnode(struct gpio_device *gdev)
> +{
> + struct device *gdev_dev;
> +
> + gdev_dev = gpio_device_to_device(gdev);
> + return dev_fwnode(gdev_dev);
You can just do a one-liner:
return dev_fwnode(gpio_device_to_device(gdev));
> +}
> +
> +static int ls2k_bmc_gpiochip_find(struct gpio_chip *gc, const void *data)
> +{
> + struct acpi_device *adev;
> + struct list_head resource_list;
> + struct resource_entry *rentry;
> + struct fwnode_handle *fwnode = gpio_dev_get_fwnode(gc->gpiodev);
> + phys_addr_t start_addr = (phys_addr_t) data;
> + int ret, found = 0;
> +
> + if (!is_acpi_node(fwnode))
> + goto out;
> +
> + adev = to_acpi_device_node(fwnode);
> + if (!adev)
> + goto out;
> +
> + INIT_LIST_HEAD(&resource_list);
> +
> + ret = acpi_dev_get_memory_resources(adev, &resource_list);
> + if (ret < 0)
> + goto out;
> + /*
> + * ACPI memory resources are ordered and only the first one is
> + * considered by the driver of the expected GPIO controller. So
> + * here we also only check the first one to see if it matches the
> + * expected address.
> + */
> + rentry = list_first_entry_or_null(&resource_list, struct
> resource_entry, node);
> + if (!rentry)
> + goto free_resource_list;
> + if (rentry->res->start == start_addr)
> + found = 1;
> +
> +free_resource_list:
> + acpi_dev_free_resource_list(&resource_list);
> +out:
> + return found;
> +}
> +
> +static struct gpio_desc *ls2k_bmc_find_gpio(struct ls2k_bmc_ddata *ddata)
> +{
> + /*
> + * In conventional way, the GPIO should be obtained through ACPI or
> + * device tree. However, when the information is not available,
> + * we should find the GPIO according to the convention of the server
> + * boards with LS2K BMC, the gpio signal reflecting the reset event
> + * of the BMC should be connected to pin 14 of the GPIO input of
> + * the first CPU node. The address of that GPIO controller is fixed.
> + */
> + static const phys_addr_t LOONGSON_GPIO_REG_BASE = 0x1FE00500;
> + static const unsigned int LS2K_BMC_RESET_GPIO = 14;
> + int ret;
> + struct gpio_device *gdev __free(gpio_device_put) = NULL;
Please declare the variable where you initialize it when using __free().
> + struct property_entry ls2k_bmc_swnode_properties[2] = { 0 };
Prefer `= { };`.
> +
> + dev_dbg(ddata->dev, "Searching for GPIO chip at address %pa\n",
> &LOONGSON_GPIO_REG_BASE);
> +
> + gdev = gpio_device_find((void *)LOONGSON_GPIO_REG_BASE,
> ls2k_bmc_gpiochip_find);
> +
No need for a blank line here.
> + if (!gdev) {
> + dev_dbg(ddata->dev, "cannot find GPIO chip at address %pa,
> deferring\n",
> + &LOONGSON_GPIO_REG_BASE);
> + return ERR_PTR(-EPROBE_DEFER);
> + }
> +
> + ls2k_bmc_swnode_properties[0] = PROPERTY_ENTRY_GPIO("gpio",
> + gpio_dev_get_fwnode(gdev), LS2K_BMC_RESET_GPIO,
> GPIO_ACTIVE_HIGH);
TBH this could become a GPIOLIB function as gpio_device_get_fwnode().
> +
> + ret = device_create_managed_software_node(ddata->dev,
> ls2k_bmc_swnode_properties, NULL);
> + if (ret) {
> + dev_err(ddata->dev, "Failed to create software node for GPIO
> reset: %d\n", ret);
> + return ERR_PTR(ret);
return dev_err_probe()? This can only be called from probe().
> + }
> +
> + return devm_gpiod_get_index(ddata->dev, NULL, 0, GPIOD_IN);
> +}
> +
> static void ls2k_bmc_cancel_wq(void *data)
> {
> struct ls2k_bmc_ddata *ddata = data;
> @@ -384,8 +462,7 @@ static void ls2k_bmc_cancel_wq(void *data)
> static int ls2k_bmc_init(struct ls2k_bmc_ddata *ddata)
> {
> struct pci_dev *pdev = to_pci_dev(ddata->dev);
> - void __iomem *gpio_base;
> - int gpio_irq, ret, val;
> + int gpio_irq, ret;
>
> ls2k_bmc_save_pci_data(pdev, ddata);
>
> @@ -402,44 +479,36 @@ static int ls2k_bmc_init(struct ls2k_bmc_ddata *ddata)
> return ret;
> }
>
> - gpio_base = ioremap(LOONGSON_GPIO_REG_BASE, LOONGSON_GPIO_REG_SIZE);
> - if (!gpio_base)
> - return -ENOMEM;
> -
> - /* Disable GPIO output */
> - val = readl(gpio_base + LOONGSON_GPIO_OEN);
> - writel(val | BIT(LS2K_BMC_RESET_GPIO), gpio_base + LOONGSON_GPIO_OEN);
> -
> - /* Enable GPIO functionality */
> - val = readl(gpio_base + LOONGSON_GPIO_FUNC);
> - writel(val & ~BIT(LS2K_BMC_RESET_GPIO), gpio_base + LOONGSON_GPIO_FUNC);
> -
> - /* Set GPIO interrupts to low-level active */
> - val = readl(gpio_base + LOONGSON_GPIO_INTPOL);
> - writel(val & ~BIT(LS2K_BMC_RESET_GPIO), gpio_base +
> LOONGSON_GPIO_INTPOL);
> -
> - /* Enable GPIO interrupts */
> - val = readl(gpio_base + LOONGSON_GPIO_INTEN);
> - writel(val | BIT(LS2K_BMC_RESET_GPIO), gpio_base + LOONGSON_GPIO_INTEN);
> + ddata->reset_gpio = devm_gpiod_get_index_optional(&pdev->dev, NULL, 0,
> GPIOD_IN);
> + if (IS_ERR(ddata->reset_gpio)) {
> + ret = PTR_ERR(ddata->reset_gpio);
> + ddata->reset_gpio = NULL;
> + return dev_err_probe(ddata->dev, ret, "Failed to get GPIO pin
> for reset signal\n");
> + }
> + if (ddata->reset_gpio == NULL) {
> + ddata->reset_gpio = ls2k_bmc_find_gpio(ddata);
> + if (IS_ERR(ddata->reset_gpio)) {
> + ret = PTR_ERR(ddata->reset_gpio);
> + ddata->reset_gpio = NULL;
> + return dev_err_probe(ddata->dev, ret,
> + "Failed to find GPIO pin for reset
> signal\n");
Why not just:
return dev_err_probe(ddata->dev, PTR_ERR(ddata->reset_gpio), ...)?
> + }
> + }
>
> - iounmap(gpio_base);
> + gpio_irq = gpiod_to_irq(ddata->reset_gpio);
>
> - /*
> - * Since gpio_chip->to_irq is not implemented in the Loongson-3 GPIO
> driver,
> - * acpi_register_gsi() is used to obtain the GPIO IRQ. The GPIO
> interrupt is a
> - * watchdog interrupt that is triggered when the BMC resets.
> - */
> - gpio_irq = acpi_register_gsi(NULL, LS2K_BMC_RESET_GPIO_GSI,
> ACPI_EDGE_SENSITIVE,
> - ACPI_ACTIVE_LOW);
> if (gpio_irq < 0)
> - return gpio_irq;
> + return dev_err_probe(ddata->dev, gpio_irq,
> + "Failed to get IRQ for GPIO reset signal
> input\n");
>
> - ret = devm_request_irq(ddata->dev, gpio_irq, ls2k_bmc_interrupt,
> - IRQF_SHARED | IRQF_TRIGGER_FALLING, "ls2kbmc
> gpio", ddata);
> - if (ret)
> - dev_err(ddata->dev, "Failed to request LS2KBMC GPIO IRQ %d.\n",
> gpio_irq);
> + ret = devm_request_irq(&pdev->dev, gpio_irq, ls2k_bmc_interrupt,
> + IRQF_SHARED | IRQF_TRIGGER_FALLING, "ls2kbmc
> reset", ddata);
> +
> + if (ret != 0)
> + return dev_err_probe(ddata->dev, ret,
> + "Failed to request IRQ %d for GPIO reset
> signal input.\n",
> + gpio_irq);
>
> - acpi_unregister_gsi(LS2K_BMC_RESET_GPIO_GSI);
> return ret;
> }
>
>
> --
> 2.49.0
>
>
>
Obviously this is ugly but I understand the need for this workaround so with
the issues above addressed, this will work for me.
Bart
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