From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 22/28] sgiseeq: convert from dma_cache_sync to dma_sync_single_for_device Date: Thu, 3 Sep 2020 10:43:02 +0200 Message-ID: <20200903084302.GB24410@lst.de> References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-23-hch@lst.de> <20200901152209.GA14288@alpha.franken.de> <20200901171241.GA20685@alpha.franken.de> <20200901171627.GA8255@lst.de> <20200901173810.GA25282@alpha.franken.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200901173810.GA25282@alpha.franken.de> Sender: linux-parisc-owner@vger.kernel.org To: Thomas Bogendoerfer Cc: Christoph Hellwig , alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, Marek Szyprowski , linux-samsung-soc@vger.kernel.org, Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , linux-media@vger.kernel.org, Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kern List-Id: nouveau.vger.kernel.org On Tue, Sep 01, 2020 at 07:38:10PM +0200, Thomas Bogendoerfer wrote: > this is the problem: > > /* Always check for received packets. */ > sgiseeq_rx(dev, sp, hregs, sregs); > > so the driver will look at the rx descriptor on every interrupt, so > we cache the rx descriptor on the first interrupt and if there was > $no rx packet, we will only see it, if cache line gets flushed for > some other reason. That means a transfer back to device ownership is missing after a (negative) check. > kick_tx() does a busy loop checking tx descriptors, > with just sync_desc_cpu... > > Thomas. > > -- > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a > good idea. [ RFC1925, 2.3 ] ---end quoted text---