Re: [PATCH 3/3] usb: gadget: f_sourcesink: Addition of SSP endpoint companion for Isochronous transfers

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Jul 04, 2025 at 05:10:13PM +0530, Srikanth Chary Chennoju wrote:
> This patch is created to support super speed plus endpoint for
> Isochronous transfers. Now super speed endpoint companion is
> accompanied by super speed plus endpoint companion.
> With this change we could see the Isoc IN and OUT performance
> reaching to ~749MB/sec which is 96K per uframe.
> The performance numbers are confirmed through Lecroy trace.

You do have a full 72 characters wide, you can use it :)

> 
> Signed-off-by: Srikanth Chary Chennoju <srikanth.chary-chennoju@amd.com>
> ---
>  drivers/usb/gadget/function/f_sourcesink.c | 23 ++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_sourcesink.c b/drivers/usb/gadget/function/f_sourcesink.c
> index 84f3b3bc7669..6499e95e0e9c 100644
> --- a/drivers/usb/gadget/function/f_sourcesink.c
> +++ b/drivers/usb/gadget/function/f_sourcesink.c
> @@ -232,6 +232,12 @@ static struct usb_ss_ep_comp_descriptor ss_iso_source_comp_desc = {
>  	.wBytesPerInterval =	cpu_to_le16(1024),
>  };
>  
> +static struct usb_ssp_isoc_ep_comp_descriptor ssp_iso_source_comp_desc = {
> +	.bLength =		USB_DT_SSP_ISOC_EP_COMP_SIZE,
> +	.bDescriptorType =	USB_DT_SSP_ISOC_ENDPOINT_COMP,
> +	.dwBytesPerInterval =	cpu_to_le32(1024),
> +};
> +
>  static struct usb_endpoint_descriptor ss_iso_sink_desc = {
>  	.bLength =		USB_DT_ENDPOINT_SIZE,
>  	.bDescriptorType =	USB_DT_ENDPOINT,
> @@ -250,6 +256,12 @@ static struct usb_ss_ep_comp_descriptor ss_iso_sink_comp_desc = {
>  	.wBytesPerInterval =	cpu_to_le16(1024),
>  };
>  
> +static struct usb_ssp_isoc_ep_comp_descriptor ssp_iso_sink_comp_desc = {
> +	.bLength =		USB_DT_SSP_ISOC_EP_COMP_SIZE,
> +	.bDescriptorType =	USB_DT_SSP_ISOC_ENDPOINT_COMP,
> +	.dwBytesPerInterval =	cpu_to_le32(1024),
> +};
> +
>  static struct usb_descriptor_header *ss_source_sink_descs[] = {
>  	(struct usb_descriptor_header *) &source_sink_intf_alt0,
>  	(struct usb_descriptor_header *) &ss_source_desc,
> @@ -264,8 +276,10 @@ static struct usb_descriptor_header *ss_source_sink_descs[] = {
>  	(struct usb_descriptor_header *) &ss_sink_comp_desc,
>  	(struct usb_descriptor_header *) &ss_iso_source_desc,
>  	(struct usb_descriptor_header *) &ss_iso_source_comp_desc,
> +	(struct usb_descriptor_header *)&ssp_iso_source_comp_desc,
>  	(struct usb_descriptor_header *) &ss_iso_sink_desc,
>  	(struct usb_descriptor_header *) &ss_iso_sink_comp_desc,
> +	(struct usb_descriptor_header *)&ssp_iso_sink_comp_desc,

Odd spacing :(

Please follow the format that was previously there.


>  	NULL,
>  };
>  
> @@ -428,7 +442,7 @@ sourcesink_bind(struct usb_configuration *c, struct usb_function *f)
>  	 */
>  	ss_iso_source_desc.wMaxPacketSize = ss->isoc_maxpacket;
>  	ss_iso_source_desc.bInterval = ss->isoc_interval;
> -	ss_iso_source_comp_desc.bmAttributes = ss->isoc_mult;
> +	ss_iso_source_comp_desc.bmAttributes = 0x80 | ss->isoc_mult;

What is 0x80 for?  Is that a #define somewhere?

>  	ss_iso_source_comp_desc.bMaxBurst = ss->isoc_maxburst;
>  	ss_iso_source_comp_desc.wBytesPerInterval = ss->isoc_maxpacket *
>  		(ss->isoc_mult + 1) * (ss->isoc_maxburst + 1);
> @@ -437,12 +451,17 @@ sourcesink_bind(struct usb_configuration *c, struct usb_function *f)
>  
>  	ss_iso_sink_desc.wMaxPacketSize = ss->isoc_maxpacket;
>  	ss_iso_sink_desc.bInterval = ss->isoc_interval;
> -	ss_iso_sink_comp_desc.bmAttributes = ss->isoc_mult;
> +	ss_iso_sink_comp_desc.bmAttributes = 0x80 | ss->isoc_mult;

Same here.

>  	ss_iso_sink_comp_desc.bMaxBurst = ss->isoc_maxburst;
>  	ss_iso_sink_comp_desc.wBytesPerInterval = ss->isoc_maxpacket *
>  		(ss->isoc_mult + 1) * (ss->isoc_maxburst + 1);
>  	ss_iso_sink_desc.bEndpointAddress = fs_iso_sink_desc.bEndpointAddress;
>  
> +	ssp_iso_source_comp_desc.dwBytesPerInterval = ss->isoc_maxpacket *
> +		(ss->isoc_mult + 1) * (ss->isoc_maxburst + 1) * 2;
> +	ssp_iso_sink_comp_desc.dwBytesPerInterval = ss->isoc_maxpacket *
> +		(ss->isoc_mult + 1) * (ss->isoc_maxburst + 1) * 2;

Why * 2?

thanks,

greg k-h