On Tue, 15 Jul 2025, Binbin Zhou wrote:
> Since the display is a sub-function of the Loongson-2K BMC, when the
> BMC reset, the entire BMC PCIe is disconnected, including the display
> which is interrupted.
>
> Quick overview of the entire LS2K BMC reset process:
>
> There are two types of reset methods: soft reset (BMC-initiated reboot
> of IPMI reset command) and BMC watchdog reset (watchdog timeout).
>
> First, regardless of the method, an interrupt is generated (PCIe interrupt
> for soft reset/GPIO interrupt for watchdog reset);
>
> Second, during the interrupt process, the system enters bmc_reset_work,
> clears the bus/IO/mem resources of the LS7A PCI-E bridge, waits for the BMC
> reset to begin, then restores the parent device's PCI configuration space,
> waits for the BMC reset to complete, and finally restores the BMC PCI
> configuration space.
>
> Display restoration occurs last.
>
> Co-developed-by: Chong Qiao <qiaoch...@loongson.cn>
> Signed-off-by: Chong Qiao <qiaoch...@loongson.cn>
> Reviewed-by: Huacai Chen <chenhua...@loongson.cn>
> Acked-by: Corey Minyard <co...@minyard.net>
> Signed-off-by: Binbin Zhou <zhoubin...@loongson.cn>
> ---
> drivers/mfd/ls2k-bmc-core.c | 328 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 328 insertions(+)
Looking good now - just a couple of nits.
I suggest that this will be applied once the merge-window closes, so no rush.
> diff --git a/drivers/mfd/ls2k-bmc-core.c b/drivers/mfd/ls2k-bmc-core.c
> index 39cc481d9ba1..bc96e42622d1 100644
> --- a/drivers/mfd/ls2k-bmc-core.c
> +++ b/drivers/mfd/ls2k-bmc-core.c
> @@ -10,8 +10,12 @@
> */
>
> #include <linux/aperture.h>
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> #include <linux/errno.h>
> #include <linux/init.h>
> +#include <linux/iopoll.h>
> +#include <linux/kbd_kern.h>
> #include <linux/kernel.h>
> #include <linux/mfd/core.h>
> #include <linux/module.h>
> @@ -19,6 +23,8 @@
> #include <linux/pci_ids.h>
> #include <linux/platform_data/simplefb.h>
> #include <linux/platform_device.h>
> +#include <linux/stop_machine.h>
> +#include <linux/vt_kern.h>
>
> /* LS2K BMC resources */
> #define LS2K_DISPLAY_RES_START (SZ_16M + SZ_2M)
> @@ -29,6 +35,48 @@
> #define LS2K_IPMI3_RES_START (LS2K_IPMI2_RES_START +
> LS2K_IPMI_RES_SIZE)
> #define LS2K_IPMI4_RES_START (LS2K_IPMI3_RES_START +
> LS2K_IPMI_RES_SIZE)
>
> +#define LS7A_PCI_CFG_SIZE 0x100
> +
> +/* LS7A bridge registers */
> +#define LS7A_PCIE_PORT_CTL0 0x0
> +#define LS7A_PCIE_PORT_STS1 0xC
> +#define LS7A_GEN2_CTL 0x80C
> +#define LS7A_SYMBOL_TIMER 0x71C
> +
> +/* Bits of LS7A_PCIE_PORT_CTL0 */
> +#define LS2K_BMC_PCIE_LTSSM_ENABLE BIT(3)
> +
> +/* Bits of LS7A_PCIE_PORT_STS1 */
> +#define LS2K_BMC_PCIE_LTSSM_STS GENMASK(5, 0)
> +#define LS2K_BMC_PCIE_CONNECTED 0x11
> +
> +#define LS2K_BMC_PCIE_DELAY_US 1000
> +#define LS2K_BMC_PCIE_TIMEOUT_US 1000000
> +
> +/* Bits of LS7A_GEN2_CTL */
> +#define LS7A_GEN2_SPEED_CHANG BIT(17)
> +#define LS7A_CONF_PHY_TX BIT(18)
> +
> +/* Bits of LS7A_SYMBOL_TIMER */
> +#define LS7A_MASK_LEN_MATCH BIT(26)
> +
> +/* Interval between interruptions */
> +#define LS2K_BMC_INT_INTERVAL (60 * HZ)
> +
> +/* Maximum time to wait for U-Boot and DDR to be ready with ms. */
> +#define LS2K_BMC_RESET_WAIT_TIME 10000
> +
> +/* It's an experience value */
> +#define LS7A_BAR0_CHECK_MAX_TIMES 2000
> +
> +#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
> +
> enum {
> LS2K_BMC_DISPLAY,
> LS2K_BMC_IPMI0,
> @@ -95,6 +143,273 @@ static struct mfd_cell ls2k_bmc_cells[] = {
> },
> };
>
> +/* Index of the BMC PCI configuration space to be restored at BMC reset. */
> +struct ls2k_bmc_pci_data {
> + u32 pci_command;
> + u32 base_address0;
> + u32 interrupt_line;
> +};
> +
> +/* Index of the parent PCI configuration space to be restored at BMC reset.
> */
> +struct ls2k_bmc_bridge_pci_data {
> + u32 pci_command;
> + u32 base_address[6];
> + u32 rom_addreess;
> + u32 interrupt_line;
> + u32 msi_hi;
> + u32 msi_lo;
> + u32 devctl;
> + u32 linkcap;
> + u32 linkctl_sts;
> + u32 symbol_timer;
> + u32 gen2_ctrl;
> +};
> +
> +struct ls2k_bmc_pdata {
> + struct device *dev;
> + struct work_struct bmc_reset_work;
> + struct ls2k_bmc_pci_data bmc_pci_data;
> + struct ls2k_bmc_bridge_pci_data bridge_pci_data;
> +};
> +
> +static bool ls2k_bmc_bar0_addr_is_set(struct pci_dev *pdev)
> +{
> + u32 addr;
> +
> + pci_read_config_dword(pdev, PCI_BASE_ADDRESS_0, &addr);
> +
> + return addr & PCI_BASE_ADDRESS_MEM_MASK ? true : false;
> +}
> +
> +static bool ls2k_bmc_pcie_is_connected(struct pci_dev *parent, struct
> ls2k_bmc_pdata *ddata)
> +{
> + void __iomem *base;
> + int sts, ret;
> +
> + base = pci_iomap(parent, 0, LS7A_PCI_CFG_SIZE);
> + if (!base)
> + return false;
> +
> + writel(readl(base + LS7A_PCIE_PORT_CTL0) | LS2K_BMC_PCIE_LTSSM_ENABLE,
> + base + LS7A_PCIE_PORT_CTL0);
Not keen on this - please separate the read from the write.
> + ret = readl_poll_timeout_atomic(base + LS7A_PCIE_PORT_STS1, sts,
> + (sts & LS2K_BMC_PCIE_LTSSM_STS) ==
> LS2K_BMC_PCIE_CONNECTED,
> + LS2K_BMC_PCIE_DELAY_US,
> LS2K_BMC_PCIE_TIMEOUT_US);
> + if (ret) {
> + pci_iounmap(parent, base);
> + dev_err(ddata->dev, "PCIE train failed status=0x%x\n", sts);
Nit: This is "PCI-E" elsewhere.
> + return false;
> + }
> +
> + pci_iounmap(parent, base);
> + return true;
> +}
> +
> +static void ls2k_bmc_restore_bridge_pci_data(struct pci_dev *parent, struct
> ls2k_bmc_pdata *ddata)
> +{
> + int base, i = 0;
> +
> + pci_write_config_dword(parent, PCI_COMMAND,
> ddata->bridge_pci_data.pci_command);
> +
> + for (base = PCI_BASE_ADDRESS_0; base <= PCI_BASE_ADDRESS_5; base += 4,
> i++)
> + pci_write_config_dword(parent, base,
> ddata->bridge_pci_data.base_address[i]);
> +
> + pci_write_config_dword(parent, PCI_ROM_ADDRESS,
> ddata->bridge_pci_data.rom_addreess);
> + pci_write_config_dword(parent, PCI_INTERRUPT_LINE,
> ddata->bridge_pci_data.interrupt_line);
> +
> + pci_write_config_dword(parent, parent->msi_cap + PCI_MSI_ADDRESS_LO,
> + ddata->bridge_pci_data.msi_lo);
> + pci_write_config_dword(parent, parent->msi_cap + PCI_MSI_ADDRESS_HI,
> + ddata->bridge_pci_data.msi_hi);
> + pci_write_config_dword(parent, parent->pcie_cap + PCI_EXP_DEVCTL,
> + ddata->bridge_pci_data.devctl);
> + pci_write_config_dword(parent, parent->pcie_cap + PCI_EXP_LNKCAP,
> + ddata->bridge_pci_data.linkcap);
> + pci_write_config_dword(parent, parent->pcie_cap + PCI_EXP_LNKCTL,
> + ddata->bridge_pci_data.linkctl_sts);
> +
> + pci_write_config_dword(parent, LS7A_GEN2_CTL,
> ddata->bridge_pci_data.gen2_ctrl);
> + pci_write_config_dword(parent, LS7A_SYMBOL_TIMER,
> ddata->bridge_pci_data.symbol_timer);
> +}
> +
> +static int ls2k_bmc_recover_pci_data(void *data)
> +{
> + struct ls2k_bmc_pdata *ddata = data;
> + struct pci_dev *pdev = to_pci_dev(ddata->dev);
> + struct pci_dev *parent = pdev->bus->self;
> + u32 i;
> +
> + /*
> + * Clear the bus, io and mem resources of the PCI-E bridge to zero, so
> that
> + * the processor can not access the LS2K PCI-E port, to avoid crashing
> due to
> + * the lack of return signal from accessing the LS2K PCI-E port.
> + */
> + pci_write_config_dword(parent, PCI_BASE_ADDRESS_2, 0);
> + pci_write_config_dword(parent, PCI_BASE_ADDRESS_3, 0);
> + pci_write_config_dword(parent, PCI_BASE_ADDRESS_4, 0);
> +
> + /*
> + * When the LS2K BMC is reset, the LS7A PCI-E port is also reset, and
> its PCI
> + * BAR0 register is cleared. Due to the time gap between the GPIO
> interrupt
> + * generation and the LS2K BMC reset, the LS7A PCI BAR0 register is
> read to
> + * determine whether the reset has begun.
> + */
> + for (i = LS7A_BAR0_CHECK_MAX_TIMES; i > 0 ; i--) {
> + if (!ls2k_bmc_bar0_addr_is_set(parent))
> + break;
> + mdelay(1);
> + };
> +
> + if (i == 0)
> + return false;
> +
> + ls2k_bmc_restore_bridge_pci_data(parent, ddata);
> +
> + /* Check if PCI-E is connected */
> + if (!ls2k_bmc_pcie_is_connected(parent, ddata))
> + return false;
> +
> + /* Waiting for U-Boot and DDR ready */
> + mdelay(LS2K_BMC_RESET_WAIT_TIME);
> + if (!ls2k_bmc_bar0_addr_is_set(parent))
> + return false;
> +
> + /* Restore LS2K BMC PCI-E config data */
> + pci_write_config_dword(pdev, PCI_COMMAND,
> ddata->bmc_pci_data.pci_command);
> + pci_write_config_dword(pdev, PCI_BASE_ADDRESS_0,
> ddata->bmc_pci_data.base_address0);
> + pci_write_config_dword(pdev, PCI_INTERRUPT_LINE,
> ddata->bmc_pci_data.interrupt_line);
> +
> + return 0;
> +}
> +
> +static void ls2k_bmc_events_fn(struct work_struct *work)
> +{
> + struct ls2k_bmc_pdata *ddata = container_of(work, struct
> ls2k_bmc_pdata, bmc_reset_work);
> +
> + /*
> + * The PCI-E is lost when the BMC resets, at which point access to the
> PCI-E
> + * from other CPUs is suspended to prevent a crash.
> + */
> + stop_machine(ls2k_bmc_recover_pci_data, ddata, NULL);
> +
> + if (IS_ENABLED(CONFIG_VT))
> + /* Re-push the display due to previous PCI-E loss. */
> + set_console(vt_move_to_console(MAX_NR_CONSOLES - 1, 1));
> +}
> +
> +static irqreturn_t ls2k_bmc_interrupt(int irq, void *arg)
> +{
> + struct ls2k_bmc_pdata *ddata = arg;
> + static unsigned long last_jiffies;
> +
> + if (system_state != SYSTEM_RUNNING)
> + return IRQ_HANDLED;
> +
> + /* Skip interrupt in LS2K_BMC_INT_INTERVAL */
> + if (time_after(jiffies, last_jiffies + LS2K_BMC_INT_INTERVAL)) {
> + schedule_work(&ddata->bmc_reset_work);
> + last_jiffies = jiffies;
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +/*
> + * Saves the BMC parent device (LS7A) and its own PCI configuration space
> registers
> + * that need to be restored after BMC reset.
> + */
> +static void ls2k_bmc_save_pci_data(struct pci_dev *pdev, struct
> ls2k_bmc_pdata *ddata)
> +{
> + struct pci_dev *parent = pdev->bus->self;
> + int base, i = 0;
> +
> + pci_read_config_dword(parent, PCI_COMMAND,
> &ddata->bridge_pci_data.pci_command);
> +
> + for (base = PCI_BASE_ADDRESS_0; base <= PCI_BASE_ADDRESS_5; base += 4,
> i++)
> + pci_read_config_dword(parent, base,
> &ddata->bridge_pci_data.base_address[i]);
> +
> + pci_read_config_dword(parent, PCI_ROM_ADDRESS,
> &ddata->bridge_pci_data.rom_addreess);
> + pci_read_config_dword(parent, PCI_INTERRUPT_LINE,
> &ddata->bridge_pci_data.interrupt_line);
> +
> + pci_read_config_dword(parent, parent->msi_cap + PCI_MSI_ADDRESS_LO,
> + &ddata->bridge_pci_data.msi_lo);
> + pci_read_config_dword(parent, parent->msi_cap + PCI_MSI_ADDRESS_HI,
> + &ddata->bridge_pci_data.msi_hi);
> +
> + pci_read_config_dword(parent, parent->pcie_cap + PCI_EXP_DEVCTL,
> + &ddata->bridge_pci_data.devctl);
> + pci_read_config_dword(parent, parent->pcie_cap + PCI_EXP_LNKCAP,
> + &ddata->bridge_pci_data.linkcap);
> + pci_read_config_dword(parent, parent->pcie_cap + PCI_EXP_LNKCTL,
> + &ddata->bridge_pci_data.linkctl_sts);
> +
> + pci_read_config_dword(parent, LS7A_GEN2_CTL,
> &ddata->bridge_pci_data.gen2_ctrl);
> + ddata->bridge_pci_data.gen2_ctrl |= FIELD_PREP(LS7A_GEN2_SPEED_CHANG,
> 0x1)
> + | FIELD_PREP(LS7A_CONF_PHY_TX, 0x0);
> +
> + pci_read_config_dword(parent, LS7A_SYMBOL_TIMER,
> &ddata->bridge_pci_data.symbol_timer);
> + ddata->bridge_pci_data.symbol_timer |= LS7A_MASK_LEN_MATCH;
> +
> + pci_read_config_dword(pdev, PCI_COMMAND,
> &ddata->bmc_pci_data.pci_command);
> + pci_read_config_dword(pdev, PCI_BASE_ADDRESS_0,
> &ddata->bmc_pci_data.base_address0);
> + pci_read_config_dword(pdev, PCI_INTERRUPT_LINE,
> &ddata->bmc_pci_data.interrupt_line);
> +}
> +
> +static int ls2k_bmc_pdata_initial(struct ls2k_bmc_pdata *ddata)
> +{
> + struct pci_dev *pdev = to_pci_dev(ddata->dev);
> + int gsi = 16 + (LS2K_BMC_RESET_GPIO & 7);
> + void __iomem *gpio_base;
> + int irq, ret;
> +
> + ls2k_bmc_save_pci_data(pdev, ddata);
> +
> + INIT_WORK(&ddata->bmc_reset_work, ls2k_bmc_events_fn);
> +
> + ret = devm_request_irq(&pdev->dev, pdev->irq, ls2k_bmc_interrupt,
> + IRQF_SHARED | IRQF_TRIGGER_FALLING, "ls2kbmc
> pcie", ddata);
> + if (ret) {
> + dev_err(ddata->dev, "Failed to request LS2KBMC PCI-E IRQ
> %d.\n", pdev->irq);
> + return ret;
> + }
> +
> + /*
> + * 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.
> + */
> + irq = acpi_register_gsi(NULL, gsi, ACPI_EDGE_SENSITIVE,
> ACPI_ACTIVE_LOW);
> + if (irq < 0)
> + return irq;
> +
> + gpio_base = ioremap(LOONGSON_GPIO_REG_BASE, LOONGSON_GPIO_REG_SIZE);
> + if (!gpio_base) {
> + ret = PTR_ERR(gpio_base);
> + goto acpi_failed;
> + }
> +
> + writel(readl(gpio_base + LOONGSON_GPIO_OEN) | BIT(LS2K_BMC_RESET_GPIO),
> + gpio_base + LOONGSON_GPIO_OEN);
> + writel(readl(gpio_base + LOONGSON_GPIO_FUNC) &
> ~BIT(LS2K_BMC_RESET_GPIO),
> + gpio_base + LOONGSON_GPIO_FUNC);
> + writel(readl(gpio_base + LOONGSON_GPIO_INTPOL) &
> ~BIT(LS2K_BMC_RESET_GPIO),
> + gpio_base + LOONGSON_GPIO_INTPOL);
> + writel(readl(gpio_base + LOONGSON_GPIO_INTEN) |
> BIT(LS2K_BMC_RESET_GPIO),
> + gpio_base + LOONGSON_GPIO_INTEN);
> +
> + ret = devm_request_irq(ddata->dev, 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",
> irq);
> +
> + iounmap(gpio_base);
> +
> +acpi_failed:
> + acpi_unregister_gsi(gsi);
> + return ret;
> +}
> +
> /*
> * Currently the Loongson-2K BMC hardware does not have an I2C interface to
> adapt to the
> * resolution. We set the resolution by presetting "video=1280x1024-16@2M"
> to the BMC memory.
> @@ -134,6 +449,7 @@ static int ls2k_bmc_parse_mode(struct pci_dev *pdev,
> struct simplefb_platform_da
> static int ls2k_bmc_probe(struct pci_dev *dev, const struct pci_device_id
> *id)
> {
> struct simplefb_platform_data pd;
> + struct ls2k_bmc_pdata *ddata;
> resource_size_t base;
> int ret;
>
> @@ -141,6 +457,18 @@ static int ls2k_bmc_probe(struct pci_dev *dev, const
> struct pci_device_id *id)
> if (ret)
> return ret;
>
> + ddata = devm_kzalloc(&dev->dev, sizeof(*ddata), GFP_KERNEL);
> + if (IS_ERR(ddata)) {
> + ret = -ENOMEM;
> + goto disable_pci;
> + }
> +
> + ddata->dev = &dev->dev;
> +
> + ret = ls2k_bmc_pdata_initial(ddata);
> + if (ret)
> + goto disable_pci;
> +
> ret = ls2k_bmc_parse_mode(dev, &pd);
> if (ret)
> goto disable_pci;
> --
> 2.47.1
>
--
Lee Jones [李琼斯]
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