linux-kernel - Re: [Discussion] USB: musb-gadget: how to fix ZLP issue in musb_g

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Date:	Wed, 15 Sep 2010 17:10:15 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	balbi@...com
CC:	Ming Lei <tom.leiming@...il.com>,
	Sergei Shtylyov <sshtylyov@...sta.com>,
	"greg@...ah.com" <greg@...ah.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	"Gadiyar, Anand" <gadiyar@...com>,
	Mike Frysinger <vapier@...too.org>
Subject: Re: [Discussion] USB: musb-gadget: how to fix ZLP issue in musb_g_tx

Hello.

Felipe Balbi wrote:

> On Wed, Sep 15, 2010 at 06:02:22AM -0500, Ming Lei wrote:
>> If so, once the dma interrupt comes, will request->actual be same
>> with request->length in musb_g_tx?  And if it is true, could we remove 
>> the
>> check for 'is_dma'?

> see that is_dma is set to true by just checking if dma in enabled in
> txcsr, it might be that dma didn't complete everything and you need to
> write txpktrdy by hand to send last short packet. So to remove that you
> would need to re-work a bit more code.

    I don't see what to rework. The last short packet should still satisfy 
(request->actual == request->length) condition, no?

> You need to know when this is a dma IRQ or an endpoint IRQ.

    We know that -- but why check it there, before (request->actual == 
request->length)?

WBR, Sergei
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