Re: [PATCH v2] usb: cdns3: gadget: fix state inconsistency on gadget init failure

[Peter Chen (CIX)]

On 26-04-01 08:10:00, Yongchao Wu wrote:
> When cdns3_gadget_start() fails, the DRD hardware is left in gadget mode
> while software state remains INACTIVE, creating hardware/software state
> inconsistency.
> 
> When switching to host mode via sysfs:
>   echo host > /sys/class/usb_role/13180000.usb-role-switch/role
> 
> The role state is not set to CDNS_ROLE_STATE_ACTIVE due to the error,
> so cdns_role_stop() skips cleanup because state is still INACTIVE.
> This violates the DRD controller design specification (Figure22),
> which requires returning to idle state before switching roles.
> 
> This leads to a synchronous external abort in xhci_gen_setup() when
> setting up the host controller:
> 
> [  516.440698] configfs-gadget 13180000.usb: failed to start g1: -19
> [  516.442035] cdns-usb3 13180000.usb: Failed to add gadget
> [  516.443278] cdns-usb3 13180000.usb: set role 2 has failed
> ...
> [ 1301.375722] xhci-hcd xhci-hcd.1.auto: xHCI Host Controller
> [ 1301.377716] Internal error: synchronous external abort: 96000010 [#1] PREEMPT SMP
> [ 1301.382485] pc : xhci_gen_setup+0xa4/0x408
> [ 1301.393391] backtrace:
>     ...
>     xhci_gen_setup+0xa4/0x408    <-- CRASH
>     xhci_plat_setup+0x44/0x58
>     usb_add_hcd+0x284/0x678
>     ...
>     cdns_role_set+0x9c/0xbc        <-- Role switch
> 
> Fix by calling cdns_drd_gadget_off() in the error path to properly
> clean up the DRD gadget state.
> 
> Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Yongchao Wu <yongchao.wu@xxxxxxxxxxxxx>

Acked-by: Peter Chen <peter.chen@xxxxxxxxxx>

Peter
> 
> ---
> Changes in v2:
>   - Update commit title to reflect state inconsistency
>   - Add more detailed description with error logs
>   - Add Fixes tag and Cc to stable
> ---
>  drivers/usb/cdns3/cdns3-gadget.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
> index d59a60a16..4cc3f2ffb 100644
> --- a/drivers/usb/cdns3/cdns3-gadget.c
> +++ b/drivers/usb/cdns3/cdns3-gadget.c
> @@ -3428,6 +3428,7 @@ static int __cdns3_gadget_init(struct cdns *cdns)
>  	ret = cdns3_gadget_start(cdns);
>  	if (ret) {
>  		pm_runtime_put_sync(cdns->dev);
> +		cdns_drd_gadget_off(cdns);
>  		return ret;
>  	}
>  
> -- 
> 2.43.0
> 
> 

-- 

Best regards,
Peter