From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Balbi Subject: Re: [PATCH 2/5] musb: use system DMA to fix Inventra DMA issue on RTL-1.4 Date: Wed, 12 May 2010 20:51:14 +0300 Message-ID: <20100512175113.GA3285@gandalf> References: <1273664979-493-1-git-send-email-ajay.gupta@ti.com> <1273664979-493-2-git-send-email-ajay.gupta@ti.com> Reply-To: me-uiRdBs8odbtmTBlB0Cgj/Q@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1273664979-493-2-git-send-email-ajay.gupta-l0cyMroinI0@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ajay Kumar Gupta Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Anand Gadiyar List-Id: linux-omap@vger.kernel.org On Wed, May 12, 2010 at 05:19:36PM +0530, Ajay Kumar Gupta wrote: > MUSB RTL version 1.4 has a hardware issue when TX and RX DMA channels are > simultaneously enabled which results in DMA lockup. I've seen it on rtl1.8 also if I remember correctly. > Use system DMA for all RX channels as a workaround of this issue as this > will have minimal throughput overhead based on the fact that Rx transfers > are done in DMA mode-0 on OMAP34x/35x platforms. > > Another approach to use PIO mode in opposite direction would increase the > cpu loading and thus using system DMA is preferred workaround. > > Signed-off-by: Anand Gadiyar > Signed-off-by: Ajay Kumar Gupta I think falling back to pio is better than this patch. It will most likely be only one transfer. Another approach is to allocate dma channels on a transfer basis. This is way too big of a problem. -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html