Re: [PATCH v10] Add device-specific reset for Qualcomm devices

[Baochen Qiang <baochen.qiang@oss.qualcomm.com>]

On 6/24/2026 2:31 AM, Jose Ignacio Tornos Martinez wrote:
> Some Qualcomm PCIe devices (WCN6855/WCN7850 WiFi cards, SDX62/SDX65 modems)
> lack working reset methods for VFIO passthrough scenarios. These devices
> have no FLR capability, advertise NoSoftRst+ (blocking PM reset), and have
> broken bus reset.
> 
> The problem manifests in VFIO passthrough scenarios:
> 
> - WCN6855 (17cb:1103) and WCN7850 (17cb:1107) WiFi devices:
>   Normal VM operation works fine, including clean shutdown/reboot.
>   However, when the VM terminates uncleanly (crash, force-off), VFIO
>   attempts to reset the device before it can be assigned to another VM.
>   Without a working reset method, the device remains in an undefined state,
>   preventing reuse.
> 
> - SDX62/SDX65 (17cb:0308) 5G modems: Never successfully initialize even
>   on first VM assignment without proper reset capability.
> 
> Add device-specific reset methods using BAR-space hardware reset registers
> that exist in these devices:
> 
> - WCN6855/WCN7850 WiFi devices use SoC global reset via BAR0 (sequence from
>   ath11k/ath12k driver: ath11k_pci_soc_global_reset(), ath11k_pci_sw_reset(),
>   ath11k_mhi_set_mhictrl_reset()):
>   - Write/clear reset bit at offset 0x3008
>   - Wait for PCIe link recovery (up to 5 seconds)
>   - Clear MHI controller SYSERR status at offset 0x38
> 
> - SDX62/SDX65 modem devices use MHI SoC reset via BAR0 (sequence from MHI
>   driver: mhi_soc_reset(), mhi_pci_reset_prepare()):
>   - Write reset request to offset 0xb0
>   - Wait 2 seconds for reset completion
> 
> These are true hardware reset mechanisms (not power management or firmware
> error recovery), providing proper device reset for VFIO scenarios.
> 
> Testing was performed on desktop platforms with M.2 WiFi and modem cards
> using M.2-to-PCIe adapters, including extensive force-reset cycling to
> verify stability.
> 
> Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
> ---
> v10:
>   - Complete redesign based on maintainer feedback (Manivannan Sadhasivam,
>     Alex Williamson): use actual hardware reset registers from
>     device drivers instead of D3hot power cycling
> v9: https://lore.kernel.org/all/20260612142638.1243895-1-jtornosm@redhat.com/
> 
>  drivers/pci/quirks.c | 118 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 118 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 431c021d7414..8ad3f214e520 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4240,6 +4240,121 @@ static int reset_hinic_vf_dev(struct pci_dev *pdev, bool probe)
>  	return 0;
>  }
>  
> +#define QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET	0x3008
> +#define QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET_V	BIT(0)
> +#define QUALCOMM_WIFI_MHISTATUS			0x48
> +#define QUALCOMM_WIFI_MHICTRL			0x38
> +#define QUALCOMM_WIFI_MHICTRL_RESET_MASK	0x2
> +
> +/*
> + * Qualcomm WiFi device-specific reset using SoC global reset via BAR0
> + * registers.
> + */
> +static int reset_qualcomm_wifi(struct pci_dev *pdev, bool probe)
> +{
> +	bool link_recovered = false;
> +	unsigned long timeout;
> +	void __iomem *bar;
> +	u32 val;
> +	u16 cmd;
> +
> +	if (probe)
> +		return 0;
> +
> +	if (pdev->current_state != PCI_D0)
> +		return -EINVAL;
> +
> +	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
> +	pci_write_config_word(pdev, PCI_COMMAND, cmd | PCI_COMMAND_MEMORY);
> +
> +	bar = pci_iomap(pdev, 0, 0);
> +	if (!bar) {
> +		pci_write_config_word(pdev, PCI_COMMAND, cmd);
> +		return -ENODEV;
> +	}
> +
> +	val = ioread32(bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);

QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET is beyond the first 4K bar area hence requires MHI
wakeup before accessing, see [1]. the wakeup callback for WCN6855 is
ath11k_pci_bus_wake_up() which calls mhi_device_get_sync(). Not sure how this can be done
here. Maybe Mani can provide some hints?

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/wireless/ath/ath11k/pcic.c#n216


> +	val |= QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET_V;
> +	iowrite32(val, bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);
> +	ioread32(bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);
> +
> +	msleep(10);
> +
> +	val &= ~QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET_V;
> +	iowrite32(val, bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);
> +	ioread32(bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);
> +
> +	msleep(10);
> +
> +	timeout = jiffies + msecs_to_jiffies(5000);
> +	while (time_before(jiffies, timeout)) {
> +		val = ioread32(bar + QUALCOMM_WIFI_PCIE_SOC_GLOBAL_RESET);
> +		if (val != 0xffffffff) {
> +			link_recovered = true;
> +			break;
> +		}
> +		msleep(20);
> +	}
> +
> +	if (!link_recovered) {
> +		pci_err(pdev, "PCIe link failed to recover after reset\n");
> +		goto out_restore;
> +	}
> +
> +	/* After SOC_GLOBAL_RESET, MHISTATUS may still have SYSERR bit set
> +	 * and thus need to set MHICTRL_RESET to clear SYSERR.
> +	 */
> +	iowrite32(QUALCOMM_WIFI_MHICTRL_RESET_MASK, bar + QUALCOMM_WIFI_MHICTRL);
> +	ioread32(bar + QUALCOMM_WIFI_MHICTRL);
> +
> +	msleep(10);
> +
> +out_restore:
> +	pci_iounmap(pdev, bar);
> +	pci_write_config_word(pdev, PCI_COMMAND, cmd);
> +
> +	return link_recovered ? 0 : -ETIMEDOUT;
> +}
> +
> +#define MHI_SOC_RESET_REQ_OFFSET		0xb0
> +#define MHI_SOC_RESET_REQ			BIT(0)
> +
> +/*
> + * Qualcomm modem device-specific reset using MHI SoC reset via BAR0
> + * register.
> + */
> +static int reset_qualcomm_modem(struct pci_dev *pdev, bool probe)
> +{
> +	void __iomem *bar;
> +	u16 cmd;
> +
> +	if (probe)
> +		return 0;
> +
> +	if (pdev->current_state != PCI_D0)
> +		return -EINVAL;
> +
> +	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
> +	pci_write_config_word(pdev, PCI_COMMAND, cmd | PCI_COMMAND_MEMORY);
> +
> +	bar = pci_iomap(pdev, 0, 0);
> +	if (!bar) {
> +		pci_write_config_word(pdev, PCI_COMMAND, cmd);
> +		return -ENODEV;
> +	}
> +
> +	iowrite32(MHI_SOC_RESET_REQ, bar + MHI_SOC_RESET_REQ_OFFSET);
> +	ioread32(bar + MHI_SOC_RESET_REQ_OFFSET);
> +
> +	/* Be sure device reset has been executed */
> +	msleep(2000);
> +
> +	pci_iounmap(pdev, bar);
> +	pci_write_config_word(pdev, PCI_COMMAND, cmd);
> +
> +	return 0;
> +}
> +
>  static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
>  	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82599_SFP_VF,
>  		 reset_intel_82599_sfp_virtfn },
> @@ -4255,6 +4370,9 @@ static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
>  		reset_chelsio_generic_dev },
>  	{ PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HINIC_VF,
>  		reset_hinic_vf_dev },
> +	{ PCI_VENDOR_ID_QCOM, 0x1103, reset_qualcomm_wifi },  /* WCN6855 WiFi */
> +	{ PCI_VENDOR_ID_QCOM, 0x1107, reset_qualcomm_wifi },  /* WCN7850 WiFi */
> +	{ PCI_VENDOR_ID_QCOM, 0x0308, reset_qualcomm_modem }, /* SDX62/SDX65 modems */
>  	{ 0 }
>  };
>