From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= Date: Wed, 6 Apr 2011 23:01:55 +0200 Subject: [RFC][PATCH] bcmai: introduce AI driver In-Reply-To: <1302123428.20093.6.camel@maggie> References: <1302033463-1846-1-git-send-email-zajec5@gmail.com> <1302123428.20093.6.camel@maggie> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org W dniu 6 kwietnia 2011 22:57 u?ytkownik Michael B?sch napisa?: > On Wed, 2011-04-06 at 22:42 +0200, Rafa? Mi?ecki wrote: >> 2011/4/6 Rafa? Mi?ecki : >> > If we want to have two drivers working on two (different) cores >> > simultaneously, we will have to add trivial mutex to group core >> > switching with core operation (read/write). >> >> With a little of work we could avoid switching and mutexes on no-host >> boards. MMIO is not limited to one core at once in such a case. > > I don't think that this is a problem at all. > All that magic does happen inside of the bus I/O handlers. > Just like SSB does it. > From a driver point of view, the I/O functions just need to > be atomic. > > For SSB it's not always 100% atomic, but we're always safe > due to some assumptions being made. But this is an SSB implementation > detail that is different from AXI. So don't look too closely > at the SSB implementation of the I/O functions. You certainly want > to implement them slightly differently in AXI. SSB currently doesn't > make use of the additional sliding windows, because they are not > available in the majority of SSB devices. > > The AXI bus subsystem will manage the sliding windows and the driver > doesn't know about the details. Sure, I've meant mutex inside bcmai (or whatever name), not on the driver side! In BCMAI: bcmai_read() { mutex_get(); switch_core(); ioread(); mutex_release(); } -- Rafa?