linux-kernel - Re: [PATCH v8 1/1] usb: cdns3: allocate TX FIFO size according to composite EP number

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Date:   Wed, 27 Apr 2022 18:57:12 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Frank Li <Frank.Li@....com>
Cc:     peter.chen@...nel.org, pawell@...ence.com, rogerq@...nel.org,
        a-govindraju@...com, linux-usb@...r.kernel.org, jun.li@....com,
        lznuaa@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 1/1] usb: cdns3: allocate TX FIFO size according to
 composite EP number

On Wed, Apr 27, 2022 at 11:35:25AM -0500, Frank Li wrote:
> Some devices have USB compositions which may require multiple endpoints.
> To get better performance, need bigger CDNS3_EP_BUF_SIZE.
> 
> But bigger CDNS3_EP_BUF_SIZE may exceed total hardware FIFO size when
> multiple endpoints.
> 
> By introducing the check_config() callback, calculate CDNS3_EP_BUF_SIZE.
> 
> Move CDNS3_EP_BUF_SIZE into cnds3_device: ep_buf_size
> Combine CDNS3_EP_ISO_SS_BURST and CDNS3_EP_ISO_HS_MULT into
> ecnds3_device:ep_iso_burst
> 
> Using a simple algorithm to calculate ep_buf_size.
> ep_buf_size = ep_iso_burst = (onchip_buffers - 2k) / (number of IN EP +
> 1).
> 
> Test at 8qxp:
> 
> 	Gadget			ep_buf_size
> 
> 	RNDIS:				5
> 	RNDIS+ACM:			3
> 	Mass Storage + NCM + ACM	2
> 
> Previous CDNS3_EP_BUF_SIZE is 4, RNDIS + ACM will be failure because
> exceed FIFO memory.
> 
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> Change from v1 to v2:
>  Add safe check for mult, buffering and maxburst

that's nice, but this is v8, not v2?

confused,

greg k-h