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

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Date:   Thu, 5 May 2022 21:31:57 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zhi Li <lznuaa@...il.com>
Cc:     Frank Li <Frank.Li@....com>, Peter Chen <peter.chen@...nel.org>,
        pawell@...ence.com, rogerq@...nel.org, a-govindraju@...com,
        linux-usb@...r.kernel.org, Jun Li <jun.li@....com>,
        kernel list <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 12:03:22PM -0500, Zhi Li wrote:
> On Wed, Apr 27, 2022 at 11:57 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > 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?
> 
> Sorry, It should be v2. I made a mistake with the title.

Ok, the next version needs to be 9 to keep everything from getting
really confused.

thanks,

greg k-h