From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Hague Subject: Re: [2.6.11 Permedia-2 Framebuffer] driver broken (?). Date: Mon, 07 Mar 2005 22:08:32 -0000 (GMT) Message-ID: References: Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1D8QPy-0005YF-P3 for linux-fbdev-devel@lists.sourceforge.net; Mon, 07 Mar 2005 14:09:38 -0800 Received: from cpc1-oxfd2-6-0-cust43.oxfd.cable.ntl.com ([81.103.191.43] helo=fluffy.bear-cave.org.uk) by sc8-sf-mx1.sourceforge.net with esmtp (TLSv1:DES-CBC3-SHA:168) (Exim 4.41) id 1D8QPx-0007Qf-1o for linux-fbdev-devel@lists.sourceforge.net; Mon, 07 Mar 2005 14:09:38 -0800 In-Reply-To: Sender: linux-fbdev-devel-admin@lists.sourceforge.net Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: Guennadi Liakhovetski Cc: linux-kernel@vger.kernel.org, linux-fbdev-devel@lists.sourceforge.net 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 fixe= s > 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 t= his=20 > option is not very enlightening... (To be honest, I've never looked closely at this but inherited it from Il= lo's 2.4 driver. Cue scrabbling around in manuals...) pm2fb programs the Permedia registers by writing to a FIFO. Normally if y= ou 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 Disc= onnect which causes the processor to keep retrying the write cycle until the FIF= O empties and the write succeeds. On the one hand this allows faster download to the Permedia because you d= on't have to check the FIFO space, but at a cost of hogging the PCI bus (and p= ossibly causing interrupt loss) until the Permedia is ready. The programmers manu= al 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 doe= s seem to turn it on, which probably shows how much I know. As to why it's sudde= nly stopped working, I have no idea. I'll try it out and see if I see the sam= e problems. --=20 Jim Hague - jim.hague@acm.org Never trust a computer you can't l= ift. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=3D6595&alloc_id=3D14396&op=3Dclick