linux-kernel - Re: [PATCH 2/6] usb: gadget: mv

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Message-ID: <20140226151913.GF30028@saruman.home>
Date:	Wed, 26 Feb 2014 09:19:13 -0600
From:	Felipe Balbi <balbi@...com>
To:	Neil Zhang <zhangwm@...vell.com>
CC:	"balbi@...com" <balbi@...com>,
	Peter Chen <Peter.Chen@...escale.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: [PATCH 2/6] usb: gadget: mv_udc: disable HW zlt for ep0

Hi,

On Tue, Feb 25, 2014 at 05:48:17PM -0800, Neil Zhang wrote:
> > > > > > > > Hardware zlt will try to send the zero length packet
> > > > > > > > automatically when the data transferd is multiple times of
> > > > > > > > max packet, this will cause issues on Windows.
> > > > > > > > So let's disable HW zlt by default.
> > > > > > >
> > > > > > > Would you have description that what kinds of issue on Windows
> > > > > > > if zlt is is selected?
> > > > > > >
> > > > > >
> > > > > > Enumeration will fail.
> > > > > >
> > > > >
> > > > > What causes enumeration fail, why it does not occur before?
> > > > >
> > > > A unexpected zero packet cause enumeration fail.
> > > > It's not easy that the descriptor is actually 1024 bytes, so not
> > > > easy to be found.
> > > >
> > >
> > > Chipidea bug too? Does it follow ch 8.5.3.2 Variable-length Data Stage, USB
> > 2.0 spec?
> > 
> > wait, this is a chipidea core ? Why aren't you guys using the chipidea driver
> > yet ? You need to switch over to that driver dude, we can't have duplicated
> > code in the tree.
> > 
> > I'm sorry, but I won't be taking this series, please use chipidea driver, it should
> > be very simple to add a glue layer for your core to the chipidea driver.
> > 
> 
> Yes, it use chipidea IP.
> But the driver is earlier than the chipidea one and we use it for our
> products.
> So it may be not that easy to switch to chipidea driver due to the
> stability.

that's nonsense, the average chipidea glue layer is ~80 LOCs. You can
write that in less than 2 hours and give it a try. We cannot have
duplicate drivers in the tree and development effort *must* be shared.

If you guys use the same IP, why wouldn't you use the same chipidea
driver ?

sorry, you didn't convince me.

-- 
balbi

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