Re: [PATCH 1/5] usb: xhci: clear stale bandwidth data after hibernation

[Michal Pecio <michal.pecio@gmail.com>]

On Tue,  6 Oct 2026 17:24:23 +0200, Niklas Neronin wrote:
> Controllers using software managed bandwidth accounting maintain
> periodic endpoint bandwidth information in struct 'xhci_interval_bw_table'.
> 
> Each root hub port owns a bandwidth table and a list of TT bandwidth
> domains, where each TT has its own bandwidth table. Virtual devices
> reference the bandwidth table of their current bandwidth domain through
> 'bw_table' or 'tt_info'.
> 
> Historically, resume from S4 re-allocated the entire xHCI driver state,
> which implicitly cleared all bandwidth accounting data. After the
> hibernation resume path was optimized to preserve parts of the driver
> state, virtual devices and TT bandwidth information were freed and
> recreated, but the root hub bandwidth tables were left intact.
> 
> As a result, stale bandwidth accounting data could remain in the root
> hub bandwidth tables across hibernation resume, leading to incorrect
> bandwidth calculations after devices were rediscovered.
> 
> Fix this by resetting all software bandwidth accounting state in
> xhci_rh_bw_cleanup() so that resume starts with a clean bandwidth state.
> This includes 'xhci->num_active_eps', which must remain consistent with
> the cleared bandwidth tables.

If that's the case then it would make sense to put this inside
xhci_rh_bw_cleanup() rather than xhci_resume(), wouldn't it?

> Fixes: <2a70e5dc0301> ("usb: xhci: optimize resuming from S4 (suspend-to-disk)")
> Reported-by: Harald Judt <h.judt@gmx.at>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=222071
> Suggested-by: Lovekesh Solanki <lovekeshsolanki00@gmail.com>
> Tested-by: Harald Judt <h.judt@gmx.at>
> Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
> ---
>  drivers/usb/host/xhci-mem.c | 16 +++++++++++++++-
>  drivers/usb/host/xhci.c     |  1 +
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index af8d4b74c4ba..75577f441cdd 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -1903,24 +1903,38 @@ EXPORT_SYMBOL_GPL(xhci_remove_secondary_interrupter);
>  void xhci_rh_bw_cleanup(struct xhci_hcd *xhci)
>  {
>  	struct xhci_root_port_bw_info *rh_bw;
> +	struct xhci_interval_bw_table *bw_table;
> +	struct xhci_interval_bw *interval_bw;
>  	struct xhci_tt_bw_info *tt_info, *tt_next;
>  	struct list_head *eps, *ep, *ep_next;
>  
>  	for (int i = 0; i < xhci->max_ports; i++) {
>  		rh_bw = &xhci->rh_bw[i];
>  
> +		rh_bw->num_active_tts = 0;
>  		/* Clear and free all TT bandwidth entries */
>  		list_for_each_entry_safe(tt_info, tt_next, &rh_bw->tts, tt_list) {
>  			list_del(&tt_info->tt_list);
>  			kfree(tt_info);
>  		}
>  
> +		bw_table = &rh_bw->bw_table;
> +		bw_table->interval0_esit_payload = 0;
> +		bw_table->bw_used = 0;
> +		bw_table->ss_bw_in = 0;
> +		bw_table->ss_bw_out = 0;
> +
>  		/* Clear per-interval endpoint lists */
>  		for (int j = 0; j < XHCI_MAX_INTERVAL; j++) {
> -			eps = &rh_bw->bw_table.interval_bw[j].endpoints;
> +			interval_bw = &bw_table->interval_bw[j];
> +			eps = &interval_bw->endpoints;
>  
> +			interval_bw->num_packets = 0;
>  			list_for_each_safe(ep, ep_next, eps)
>  				list_del_init(ep);
> +			interval_bw->overhead[LS_OVERHEAD_TYPE] = 0;
> +			interval_bw->overhead[FS_OVERHEAD_TYPE] = 0;
> +			interval_bw->overhead[HS_OVERHEAD_TYPE] = 0;
>  		}
>  	}
>  }
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index a9e47e178c28..4708fabba84a 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -1185,6 +1185,7 @@ int xhci_resume(struct xhci_hcd *xhci, bool power_lost, bool is_auto_resume)
>  		for (int i = xhci->max_slots; i > 0; i--)
>  			xhci_free_virt_devices_depth_first(xhci, i);
>  
> +		xhci->num_active_eps = 0;
>  		xhci_rh_bw_cleanup(xhci);
>  
>  		xhci->cmd_ring_reserved_trbs = 0;
> -- 
> 2.50.1
>