2010/11/25 Zhang, Sonic <Sonic.Zhang@xxxxxxxxxx>: > > >>-----Original Message----- >>From: Ming Lei [mailto:tom.leiming@xxxxxxxxx] >>Sent: Thursday, November 25, 2010 6:25 PM >>To: Anand Gadiyar >>Cc: balbi@xxxxxx; Bob Liu; Zhang, Sonic; Mike Frysinger; >>uclinux-dist-devel@xxxxxxxxxxxxxxxxxxxx; Ajay Kumar Gupta; >>linux-usb@xxxxxxxxxxxxxxx >>Subject: Re: [PATCH] musb_host: Fix high bandwidth iso transfer issue >> >>2010/11/25 Anand Gadiyar <gadiyar@xxxxxx>: >>> Felipe Balbi wrote: >>>> Hi, >>>> >>>> On Thu, Nov 25, 2010 at 04:54:05PM +0800, Bob Liu wrote: >>>> >>> The only work around is to config the receive FIFO into single >>> buffer >>>> >>> mode. >>>> >> >>>> >> And how to do that ? >>>> >> >>>> > >>>> >It's used to by "USB: musb: disable double buffering for older RTL >>>> >versions" >>>> >>>>http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git >>;a=commit >>>>dif >>> f;h=9f445cb29918dc488b7a9a92ef018599cce33df7 >>>> >>>> yeah, but that breaks other stuff high bandwidth eps, so we need a >>>> better way to "disable double buffering". >>>> >>> >>> Here's how I understand the problem. >>> >>> Blackfin has a statically configured fifo allocation - with no >>> possibility to change it. The IP uses double buffering by >>default if a >>> FIFO is allocated space enough to hold 2*maxp (which is the case for >>> at least some of the endpoints). >>> >>> The only way to make the IP use single buffering is to tell the IP >>> that the maxp is different. >>> >>> This is an anomaly only in the blackfin - I don't see any >>way to work >>> around this (for lack of information), than what has been >>implemented >>> in the patch that already got merged. >> >>Yes, I agree. >> >>> >>> However, that code should be made to execute only on >>blackfin and not >>> on other platforms - so that the others are not broken by >>that change. >> >>Even in blackfin platform, the code may break some function, >>especially for full speed device, which was explained a lot in >>the previous discussion: >> >> http://marc.info/?t=128576512000002&r=1&w=2 >> > > Hi Ming Lei, > > This is not a problem for blackfin, because there is no real use case in USB gadget full speed mode from blackfin customers we perceived. But, corrupted RX No, if the usb host works at full speed, your musb gadget will work at full speed too. Also for musb host mode, if the device connected into musb port is a full speed device, your musb host(at least the endpoint involved) still may works at full speed. >data in double buffer mode is a critical issue. So, this is an acceptable trade-off >for blackfin. -- Lei Ming -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
