From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 8 Oct 2015 17:47:35 +0200 From: Gilles Chanteperdrix Message-ID: <20151008154735.GG8324@hermes.click-hack.org> References: <561568AE.30109@xenomai.org> <56156AB4.2080705@xenomai.org> <56161232.50803@xenomai.org> <20151008144340.GE21923@csclub.uwaterloo.ca> <5616838F.7030507@xenomai.org> <20151008151744.GG21923@csclub.uwaterloo.ca> <56168EB5.10104@xenomai.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56168EB5.10104@xenomai.org> Subject: Re: [Xenomai] Interrupt latency close to 1ms on powerpc Xenomai 2.6.4 List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: "Xenomai@xenomai.org" On Thu, Oct 08, 2015 at 05:41:41PM +0200, Philippe Gerum wrote: > On 10/08/2015 05:17 PM, Lennart Sorensen wrote: > > On Thu, Oct 08, 2015 at 04:54:07PM +0200, Philippe Gerum wrote: > >> I could not find one that would not look weird. That logic is deeply > >> buried in kernel space, and introducing a dynamic dependency on whether > >> e.g. the PCI layer has to be traversed for carrying out such ops would > >> be rather confusing for the end user, especially when porting the > >> application code over different SoCs. > > > > Yep, that sounds ugly. > > > >> Likely, yes. The relevant handlers dealing with the interrupt controller > >> of the QUICC Engine do not tread on problematic code, so this should be > >> ok for this platform. > > > > Then I have the icky situation that we want the same kernel source to > > run on arm. I wonder if the am572x would care. I guess I could #ifdef > > it for powerpc only and leave the new way on arm. > > > > No guarantee, I only had a quick look at this, but AFAICS: > > - the irqchip from the PCA953X gpio extender module does not seem to > have any requirement for running over a regular kernel context > > - the main GIC IRQ controller is fine, since the fast ack code we use > over the head domain is shared with the IRQ enabling/disabling support. > > So this should be ok (famous last words). The GIC has some board/SOC specific callbacks, so, you have to check these callbacks too, to be sure that the code does not use some linux services. -- Gilles. https://click-hack.org