From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753103AbbC0ToX (ORCPT ); Fri, 27 Mar 2015 15:44:23 -0400 Received: from mail-lb0-f176.google.com ([209.85.217.176]:35591 "EHLO mail-lb0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752381AbbC0ToR convert rfc822-to-8bit (ORCPT ); Fri, 27 Mar 2015 15:44:17 -0400 MIME-Version: 1.0 In-Reply-To: <20150327193813.GH5622@wotan.suse.de> References: <1426893517-2511-1-git-send-email-mcgrof@do-not-panic.com> <1426893517-2511-10-git-send-email-mcgrof@do-not-panic.com> <20150321091514.GA22926@sci.fi> <20150327193813.GH5622@wotan.suse.de> From: Andy Lutomirski Date: Fri, 27 Mar 2015 12:43:55 -0700 Message-ID: Subject: Re: [PATCH v1 09/47] vidoe: fbdev: atyfb: remove and fix MTRR MMIO "hole" work around To: "Luis R. Rodriguez" Cc: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , Bjorn Helgaas , "Luis R. Rodriguez" , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Juergen Gross , Jan Beulich , Borislav Petkov , Suresh Siddha , venkatesh.pallipadi@intel.com, Dave Airlie , "linux-kernel@vger.kernel.org" , Linux Fbdev development list , X86 ML , "xen-devel@lists.xenproject.org" , Ingo Molnar , Linus Torvalds , Daniel Vetter , Antonino Daplas , Jean-Christophe Plagniol-Villard , Tomi Valkeinen Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 27, 2015 at 12:38 PM, Luis R. Rodriguez wrote: > On Sat, Mar 21, 2015 at 11:15:14AM +0200, Ville Syrjälä wrote: >> On Fri, Mar 20, 2015 at 04:17:59PM -0700, Luis R. Rodriguez wrote: >> > diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c >> > index 8025624..8875e56 100644 >> > --- a/drivers/video/fbdev/aty/atyfb_base.c >> > +++ b/drivers/video/fbdev/aty/atyfb_base.c >> > @@ -2630,21 +2630,10 @@ static int aty_init(struct fb_info *info) >> > >> > #ifdef CONFIG_MTRR >> > par->mtrr_aper = -1; >> > - par->mtrr_reg = -1; >> > if (!nomtrr) { >> > - /* Cover the whole resource. */ >> > - par->mtrr_aper = mtrr_add(par->res_start, par->res_size, >> > + par->mtrr_aper = mtrr_add(info->fix.smem_start, >> > + info->fix.smem_len, >> > MTRR_TYPE_WRCOMB, 1); >> >> MTRRs need power of two size, so how is this supposed to work? > > As per mtrr_add_page() [0] the base and size are just supposed to be in units > of 4 KiB, although the practice is to use powers of 2 in *some* drivers this > is not standardized and by no means recorded as a requirement. Obviously > powers of 2 will work too and you'd end up neatly aligned as well. mtrr_add() > will use mtrr_check() to verify the the same requirement. Furthermore, > as per my commit log message: Whatever the code may or may not do, the x86 architecture uses power-of-two MTRR sizes. So I'm confused. --Andy > > --- > The last thing we do must do to remain sane is ensure we > use the info->fix.smem_start and info->fix.smem_len for > the framebuffer MTRR as we know that is always well adjusted. > The *one* concern here would be if the MTRR is not in units > of 4K __but__ we already know that in the PCI case this cannot > happen, in the shared space setting the MTRR would be up to > 0x7ff000 and assuming a 4K page: > > ; 0x7ff000 / 0x1000 > 2047 > > Also, internally when MTRR is used mtrr_add() will use mtrr_check() > and that should splat a warning when the MTRR base and size are > not compatible with what is expected for MTRR usage. > --- > > If any of this is too risky we can use the __arch_phys_wc_add() (or as > Andy suggested perhaps use set_page_* stuff, although I am still evaluating > this) but I did this change to show the effort required for a change when > the registers / framebuffer is on the same PCI BAR but at different offsets. > > [0] scripts/kernel-doc -man -function mtrr_add_page arch/x86/kernel/cpu/mtrr/main.c | nroff -man | less > > Luis -- Andy Lutomirski AMA Capital Management, LLC From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Date: Fri, 27 Mar 2015 19:43:55 +0000 Subject: Re: [PATCH v1 09/47] vidoe: fbdev: atyfb: remove and fix MTRR MMIO "hole" work around Message-Id: List-Id: References: <1426893517-2511-1-git-send-email-mcgrof@do-not-panic.com> <1426893517-2511-10-git-send-email-mcgrof@do-not-panic.com> <20150321091514.GA22926@sci.fi> <20150327193813.GH5622@wotan.suse.de> In-Reply-To: <20150327193813.GH5622@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: "Luis R. Rodriguez" Cc: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , Bjorn Helgaas , "Luis R. Rodriguez" , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Juergen Gross , Jan Beulich , Borislav Petkov , Suresh Siddha , venkatesh.pallipadi@intel.com, Dave Airlie , "linux-kernel@vger.kernel.org" , Linux Fbdev development list , X86 ML , "xen-devel@lists.xenproject.org" , Ingo Molnar , Linus Torvalds , Daniel Vetter , Antonino Daplas , Jean-Christophe Plagniol-Villard , Tomi Valkeinen On Fri, Mar 27, 2015 at 12:38 PM, Luis R. Rodriguez wrote: > On Sat, Mar 21, 2015 at 11:15:14AM +0200, Ville Syrjälä wrote: >> On Fri, Mar 20, 2015 at 04:17:59PM -0700, Luis R. Rodriguez wrote: >> > diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c >> > index 8025624..8875e56 100644 >> > --- a/drivers/video/fbdev/aty/atyfb_base.c >> > +++ b/drivers/video/fbdev/aty/atyfb_base.c >> > @@ -2630,21 +2630,10 @@ static int aty_init(struct fb_info *info) >> > >> > #ifdef CONFIG_MTRR >> > par->mtrr_aper = -1; >> > - par->mtrr_reg = -1; >> > if (!nomtrr) { >> > - /* Cover the whole resource. */ >> > - par->mtrr_aper = mtrr_add(par->res_start, par->res_size, >> > + par->mtrr_aper = mtrr_add(info->fix.smem_start, >> > + info->fix.smem_len, >> > MTRR_TYPE_WRCOMB, 1); >> >> MTRRs need power of two size, so how is this supposed to work? > > As per mtrr_add_page() [0] the base and size are just supposed to be in units > of 4 KiB, although the practice is to use powers of 2 in *some* drivers this > is not standardized and by no means recorded as a requirement. Obviously > powers of 2 will work too and you'd end up neatly aligned as well. mtrr_add() > will use mtrr_check() to verify the the same requirement. Furthermore, > as per my commit log message: Whatever the code may or may not do, the x86 architecture uses power-of-two MTRR sizes. So I'm confused. --Andy > > --- > The last thing we do must do to remain sane is ensure we > use the info->fix.smem_start and info->fix.smem_len for > the framebuffer MTRR as we know that is always well adjusted. > The *one* concern here would be if the MTRR is not in units > of 4K __but__ we already know that in the PCI case this cannot > happen, in the shared space setting the MTRR would be up to > 0x7ff000 and assuming a 4K page: > > ; 0x7ff000 / 0x1000 > 2047 > > Also, internally when MTRR is used mtrr_add() will use mtrr_check() > and that should splat a warning when the MTRR base and size are > not compatible with what is expected for MTRR usage. > --- > > If any of this is too risky we can use the __arch_phys_wc_add() (or as > Andy suggested perhaps use set_page_* stuff, although I am still evaluating > this) but I did this change to show the effort required for a change when > the registers / framebuffer is on the same PCI BAR but at different offsets. > > [0] scripts/kernel-doc -man -function mtrr_add_page arch/x86/kernel/cpu/mtrr/main.c | nroff -man | less > > Luis -- Andy Lutomirski AMA Capital Management, LLC