Re: [PATCH v3] Bluetooth: btintel_pcie: fix stale cache in set_dxstate fallback check

[Paul Menzel <pmenzel@molgen.mpg.de>]

Dear Vladimir,


Thank you for the third patch iteration.

Am 03.09.26 um 16:29 schrieb Vladimir V. Kondratyev:
> btintel_pcie returns -16 (EBUSY) during suspend, causing the entire suspend
> operation to abort on Intel Lunar Lake hardware. The system immediately resumes
> after every suspend attempt:
>    Bluetooth: hci0: Timeout (200 ms) on alive interrupt for D2 entry, retry count 0
>    Bluetooth: hci0: Timeout (200 ms) on alive interrupt for D2 entry, retry count 1
>    Bluetooth: hci0: Timeout (200 ms) on alive interrupt for D2 entry, retry count 2
>    btintel_pcie 0000:00:14.7: PM: pci_pm_suspend(): btintel_pcie_suspend [btintel_pcie] returns -16
>    btintel_pcie 0000:00:14.7: PM: dpm_run_callback(): pci_pm_suspend returns -16
>    btintel_pcie 0000:00:14.7: PM: failed to suspend async: error -16
>    PM: Some devices failed to suspend, or early wake event detected
> 
> btintel_pcie_set_dxstate() falls back to checking the controller state via
> btintel_pcie_in_d3/d0() when the alive interrupt is missed. However, these
> helpers read boot_stage_cache, which is only updated by the interrupt
> handler. As such, if the interrupt was missed, the cache is stale and the
> fallback check always fails, exhausting all retries and returning -EBUSY,
> causing suspend to abort.
> 
> The fix involves re-reading the hardware register before the fallback state
> check, consistent with btintel_pcie_resume().
> 
> Fixes: e57362f4911b ("Bluetooth: btintel_pcie: Add support for _suspend() / _resume()")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=221481
> Link: https://lore.kernel.org/linux-bluetooth/20260830151550.44687-1-lsa.uz@pm.me/
> Signed-off-by: Vladimir V. Kondratyev <vladimirkondratyev2@gmail.com>
> Tested-by: Sergey Lebedev <lsa.uz@pm.me>
> ---
>   drivers/bluetooth/btintel_pcie.c | 8 +++++---
>   drivers/bluetooth/btintel_pcie.h | 1 +
>   2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/bluetooth/btintel_pcie.c b/drivers/bluetooth/btintel_pcie.c
> index fda474406003..e13631e94214 100644
> --- a/drivers/bluetooth/btintel_pcie.c
> +++ b/drivers/bluetooth/btintel_pcie.c
> @@ -2777,10 +2777,12 @@ static int btintel_pcie_set_dxstate(struct btintel_pcie_data *data, u32 dxstate)
>   					  BTINTEL_PCIE_CSR_MSIX_HW_INT_CAUSES,
>   					  BTINTEL_PCIE_MSIX_HW_INT_CAUSES_GP0);
>   
> -		/* A hardware bug may cause the alive interrupt to be missed.
> -		 * Check if the controller reached the expected state and retry
> -		 * the operation only if it hasn't.
> +		/* A hardware bug may cause the alive interrupt to be missed. Refresh
> +		 * boot_stage_cache from hardware, since only the interrupt handler
> +		 * updates it. Finally retry only if the state check still fails.
>   		 */
> +		data->boot_stage_cache = btintel_pcie_rd_reg32(data,
> +							       BTINTEL_PCIE_CSR_BOOT_STAGE_REG);
>   		if (dxstate == BTINTEL_PCIE_STATE_D0) {
>   			if (btintel_pcie_in_d0(data))
>   				return 0;
> diff --git a/drivers/bluetooth/btintel_pcie.h b/drivers/bluetooth/btintel_pcie.h
> index 2db85f71b2f8..f287d1ff8e27 100644
> --- a/drivers/bluetooth/btintel_pcie.h
> +++ b/drivers/bluetooth/btintel_pcie.h
> @@ -53,6 +53,7 @@
>   #define BTINTEL_PCIE_CSR_BOOT_STAGE_DEVICE_HALTED	(BIT(14))
>   #define BTINTEL_PCIE_CSR_BOOT_STAGE_MAC_ACCESS_ON	(BIT(16))
>   #define BTINTEL_PCIE_CSR_BOOT_STAGE_ALIVE		(BIT(23))
> +/* Reflects live D-state. Updated by hardware on every D-state transition. */
>   #define BTINTEL_PCIE_CSR_BOOT_STAGE_D3_STATE_READY	(BIT(24))
>   
>   /* Registers for MSI-X */

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul