Date: Tue, 13 Jan 2015 16:27:18 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Ian Lepore <ian@freebsd.org>, kott <kmatpral@yahoo.com> Cc: freebsd-usb@freebsd.org Subject: Re: usb_pc_cpu_flush Message-ID: <54B53956.4090708@selasky.org> In-Reply-To: <1421160576.14601.175.camel@freebsd.org> References: <1419359192795-5975583.post@n5.nabble.com> <5499E734.1070507@selasky.org> <1419392511197-5975691.post@n5.nabble.com> <549A811D.3060204@selasky.org> <1419416870924-5975752.post@n5.nabble.com> <1419423740820-5975763.post@n5.nabble.com> <549AB711.8070005@selasky.org> <1419431704871-5975773.post@n5.nabble.com> <549BF430.8000207@selasky.org> <1419877515606-5976832.post@n5.nabble.com> <1421133295061-5980199.post@n5.nabble.com> <1421160576.14601.175.camel@freebsd.org>
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On 01/13/15 15:49, Ian Lepore wrote:
> On Tue, 2015-01-13 at 00:14 -0700, kott wrote:
>> Yes with cache disabled, this problem is not seen. Seems to be with a issue
>> with l2 cache.
>> Thanks kott
>
> Except that there are no known problems with l2 cache on armv7 right
> now. There are known problems with the USB driver using the busdma
> routines incorrectly, which accidentally works okay on x86 platforms but
> likely not so well on others.
>
Hi,
If there is a problem it is in "usb_pc_cpu_flush()" or
"usb_pc_cpu_invalidate()":
void
usb_pc_cpu_flush(struct usb_page_cache *pc)
{
if (pc->page_offset_end == pc->page_offset_buf) {
/* nothing has been loaded into this page cache! */
return;
}
bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_PREWRITE);
}
USB has a very simple DMA sync language, either flush or invalidate.
These are used correctly from what I can see with regard to the FreeBSD
USB specification.
If the "usb_pc_cpu_flush()" function does not cause the CPU cache to be
written to RAM before the function returns, please let me know.
--HPS
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