Re: [PATCH v3 1/2] usb: dwc3: host: Set XHCI_SG_TRB_CACHE_SIZE_QUIRK

[Thinh Nguyen]

On Tue, Jan 16, 2024, Prashanth K wrote:
> Upstream commit bac1ec551434 ("usb: xhci: Set quirk for
> XHCI_SG_TRB_CACHE_SIZE_QUIRK") introduced a new quirk in XHCI
> which fixes XHC timeout, which was seen on synopsys XHCs while
> using SG buffers. But the support for this quirk isn't present
> in the DWC3 layer.
> 
> We will encounter this XHCI timeout/hung issue if we run iperf
> loopback tests using RTL8156 ethernet adaptor on DWC3 targets
> with scatter-gather enabled. This gets resolved after enabling
> the XHCI_SG_TRB_CACHE_SIZE_QUIRK. This patch enables it using
> the xhci device property since its needed for DWC3 controller.
> 
> In Synopsys DWC3 databook,
> Table 9-3: xHCI Debug Capability Limitations
> Chained TRBs greater than TRB cache size: The debug capability
> driver must not create a multi-TRB TD that describes smaller
> than a 1K packet that spreads across 8 or more TRBs on either
> the IN TR or the OUT TR.
> 
> Cc: <stable@xxxxxxxxxxxxxxx> #5.11
> Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
> ---
>  drivers/usb/dwc3/host.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
> index 61f57fe5bb78..43230915323c 100644
> --- a/drivers/usb/dwc3/host.c
> +++ b/drivers/usb/dwc3/host.c
> @@ -61,7 +61,7 @@ static int dwc3_host_get_irq(struct dwc3 *dwc)
>  
>  int dwc3_host_init(struct dwc3 *dwc)
>  {
> -	struct property_entry	props[4];
> +	struct property_entry	props[5];
>  	struct platform_device	*xhci;
>  	int			ret, irq;
>  	int			prop_idx = 0;
> @@ -89,6 +89,8 @@ int dwc3_host_init(struct dwc3 *dwc)
>  
>  	memset(props, 0, sizeof(struct property_entry) * ARRAY_SIZE(props));
>  
> +	props[prop_idx++] = PROPERTY_ENTRY_BOOL("xhci-sg-trb-cache-size-quirk");
> +
>  	if (dwc->usb3_lpm_capable)
>  		props[prop_idx++] = PROPERTY_ENTRY_BOOL("usb3-lpm-capable");
>  
> -- 
> 2.25.1
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>

Thanks,
Thinh