From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sven Luther Subject: Re: Large framebuffers and HIGHMEM systems Date: Wed, 10 Sep 2003 17:56:03 +0200 Sender: linux-fbdev-devel-admin@lists.sourceforge.net Message-ID: <20030910155603.GA15485@iliana> References: <20030910150100.89767.qmail@web14914.mail.yahoo.com> Mime-Version: 1.0 Return-path: 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 (Cipher TLSv1:DES-CBC3-SHA:168) (Exim 3.31-VA-mm2 #1 (Debian)) id 19x7Ki-0008Js-00 for ; Wed, 10 Sep 2003 08:56:40 -0700 Received: from smtp1.wanadoo.fr ([193.252.22.23] helo=mwinf0803.wanadoo.fr) by sc8-sf-mx1.sourceforge.net with esmtp (Exim 4.22) id 19x7Kh-0001KC-Cs for linux-fbdev-devel@lists.sourceforge.net; Wed, 10 Sep 2003 08:56:39 -0700 Content-Disposition: inline In-Reply-To: <20030910150100.89767.qmail@web14914.mail.yahoo.com> Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: List-Unsubscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jon Smirl Cc: Geert Uytterhoeven , fb-devel On Wed, Sep 10, 2003 at 08:01:00AM -0700, Jon Smirl wrote: > --- Geert Uytterhoeven wrote: > > Or modify ioremap() to print the message? This problem is not only limited to > > frame buffer devices, but to every driver that needs to ioremap() large > > regions, right? > > > ioremap() is supposed to map the region into the bottom 1GB or fail. After > ioremap() fails you need to use a different API to map to the highmem regions. > The way Linux is set up there is always about 20-30MB of free address space > below 1GB. All of the hardware I've seen can map into that space. The only > exception is the huge amount of address space needed for kernel mapped video > frame buffers. > > Memory below 1GB is important to the kernel for keeping page tables. Page table > can be pushed above 1GB but you incur performance penalties. There is no > problem creating a 256MB hole with reserve=XXXX in the 1GB address space to > allow the latest ATI/NV cards to run with framebuffers; but doing this will > slow your system down. It is also a very non-obvious solution to why a > framebuffer fails to load. > > I don't think we should be forcing non-performance sensitve framebuffer memory > into the bottom 1GB and pushing performance sensitive page tables into highmem. > Besides, we are going that have to do something, we are likely to have 1GB > video cards two years from now. We already have 512MB ones, i guess you will not have to wait for as long as two years for 1GB video cards. Friendly, Sven Luther ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf