Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261267AbVCGWzH (ORCPT ); Mon, 7 Mar 2005 17:55:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261256AbVCGWya (ORCPT ); Mon, 7 Mar 2005 17:54:30 -0500 Received: from cpc1-oxfd2-6-0-cust43.oxfd.cable.ntl.com ([81.103.191.43]:18441 "EHLO fluffy.bear-cave.org.uk") by vger.kernel.org with ESMTP id S261854AbVCGWJ1 (ORCPT ); Mon, 7 Mar 2005 17:09:27 -0500 Message-ID: X-Mailer: XFMail 1.5.4 on Linux X-Priority: 3 (Normal) Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT MIME-Version: 1.0 In-Reply-To: Date: Mon, 07 Mar 2005 22:08:32 -0000 (GMT) X-Face: #e_3/{lz7I8PY]c%cr|7\sfMTD|Ar*F0e~U%InA`aG0^}hG2hT`H9Lr=R?Nl,9-cP)_o}BN DAB"m_&V"ntfjv%6q30^]Q\NTny77`@0?P@FpO{b*dM409XvO$kmP [~W=-Cm~|#49QE;@'K}LGK}??aD=>|x=B:n6"`}!9FIrtfOx%`hTC5#VFORluPrtN_#-_6b,Cu^NF| :D=97AFz\(mw=K Organization: The Bear Cave From: Jim Hague To: Guennadi Liakhovetski Subject: Re: [2.6.11 Permedia-2 Framebuffer] driver broken (?). Cc: linux-kernel@vger.kernel.org, linux-fbdev-devel@lists.sourceforge.net Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2150 Lines: 45 Hi Guennadi, > Thanks for the patch. Yes, it does fix switching between X and VT. OK, good. > As for colours / graphics, disabling CONFIG_FB_PM2_FIFO_DISCONNECT fixes > that too, but it worked under 2.6.10-rc2 with that option on too. What does > it do and why I cannot use it under 2.6.11 any more? The help text to this > option is not very enlightening... (To be honest, I've never looked closely at this but inherited it from Illo's 2.4 driver. Cue scrabbling around in manuals...) pm2fb programs the Permedia registers by writing to a FIFO. Normally if you attempt to write to the FIFO and the FIFO is full, the write is lost. So pm2fb checks before writing that there is sufficient space in the FIFO to hold the full command sequence, and if not it loops waiting for the FIFO to empty sufficiently. Enabling FIFO_DISCONNECT enables PCI Disconnect. In this mode, if a write to the FIFO occurs when the FIFO is full, the Permedia chip enables PCI Disconnect which causes the processor to keep retrying the write cycle until the FIFO empties and the write succeeds. On the one hand this allows faster download to the Permedia because you don't have to check the FIFO space, but at a cost of hogging the PCI bus (and possibly causing interrupt loss) until the Permedia is ready. The programmers manual cautions that it should only be used when you know that the Permedia can consume data faster than the host can generate it and/or where there are no time-critical periperals on the PCI bus. All of which sounds to me like enabling PCI Disconnect isn't a great idea and offers at best infinitesimal speedups. Having said that, the X driver does seem to turn it on, which probably shows how much I know. As to why it's suddenly stopped working, I have no idea. I'll try it out and see if I see the same problems. -- Jim Hague - jim.hague@acm.org Never trust a computer you can't lift. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/