Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751899AbbD2V5V (ORCPT ); Wed, 29 Apr 2015 17:57:21 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:32898 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751303AbbD2V5T (ORCPT ); Wed, 29 Apr 2015 17:57:19 -0400 From: "Luis R. Rodriguez" To: mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, bp@suse.de, plagnioj@jcrosoft.com, tomi.valkeinen@ti.com, daniel.vetter@intel.com, airlied@linux.ie Cc: dledford@redhat.com, awalls@md.metrocast.net, syrjala@sci.fi, luto@amacapital.net, mst@redhat.com, cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org, "Luis R. Rodriguez" , Toshi Kani , Suresh Siddha , Linus Torvalds , Juergen Gross , Daniel Vetter , Dave Airlie , Antonino Daplas , Rob Clark , Mathias Krause , Andrzej Hajda , Mel Gorman , Vlastimil Babka , Davidlohr Bueso , linux-fbdev@vger.kernel.org Subject: [PATCH v4 5/6] video: fbdev: atyfb: replace MTRR UC hole with strong UC Date: Wed, 29 Apr 2015 14:44:10 -0700 Message-Id: <1430343851-967-6-git-send-email-mcgrof@do-not-panic.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1430343851-967-1-git-send-email-mcgrof@do-not-panic.com> References: <1430343851-967-1-git-send-email-mcgrof@do-not-panic.com> MIME-Version: 1.0 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 Content-Length: 9961 Lines: 252 From: "Luis R. Rodriguez" Replace a WC MTRR call followed by a UC MTRR "hole" call with a single WC MTRR call and use strong UC to protect the MMIO region and account for the device's architecture and MTRR size requirements. The atyfb driver relies on two overlapping MTRRs. It does this to account for the fact that on some devices it has the MMIO region bundled together with the framebuffer on the same PCI BAR and the hardware requirement on MTRRs on both base and size to be powers of two. In the atyfb driver's case in the worst case the PCI BAR is of 16 MiB while the MMIO region is on the last 4 KiB of the same PCI BAR. If we use just one MTRR for WC we can only end up with an 8 MiB or 16 MiB framebuffer. Using a 16 MiB WC framebuffer area is unacceptable since we need the MMIO region to not be write-combined. An 8 MiB WC framebuffer option does not let use quite a bit of framebuffer space, it would reduce the resolution capability of the device considerably. An alternative is to use many MTRRs but on some systems that could mean not having not enough MTRRs to cover the framebuffer. The current driver solution is to issue a 16 MiB WC MTRR followed by a 4 KiB UC MTRR on the last 4 KiB. Its worth mentioning and documenting that the current ioremap*() strategy as well: the first ioremap() is used only for the MMIO region, a second ioremap() call is used for the framebuffer *and* the MMIO region, the MMIO region then ends up mmap'd twice. Two ioremap() calls are used since in some situations the framebuffer actually ends up on a separate auxiliary PCI BAR, but this is not always true, in the worst case the PCI BAR is shared for both MMIO and the framebuffer. By allowing overlapping ioremap() calls the driver enables two types of devices with one simple ioremap() strategy. For non PAT systems: As per Intel SDM "11.5.2.1 Selecting Memory Types for Pentium Pro and Pentium II Processors" [0] the effect of a WC MTRR for a region with page attribute settings set to PCD=1, PWT=1 (Linux _PAGE_CACHE_MODE_UC) will render the effective memory type to UC. A WC MTRR for a region with page attribute settings set to PCD=1, PWT=0 (Linux _PAGE_CACHE_MODE_UC_MINUS) will render the effective memory type to WC *but* yet this is considered implementation defined -- that is, "system designers are encouraged to avoid these implementation-defined combinations". A WC MTRR for a region with page attribute settings set to PCD=0, PWT=1 (Linux _PAGE_CACHE_MODE_WC) will render the effective memory type to WC *but* this is also implementation defined. Such is the case for non-PAT systems. For PAT systems: As per Intel SDM "11.5.2.2 Selecting Memory Types for Pentium III and More Recent Processor Families" the ffect of a WC MTRR for a region with a PAT entry value of UC will be UC. The effect of a WC MTRR on a region with a PAT entry UC- will be WC. The effect of a WC MTRR on a regoin with PAT entry WC is WC. This can all be summarized in the following table: ---------------------------------------------------------------------- MTRR Non-PAT PAT Linux ioremap value Effective memory type ---------------------------------------------------------------------- Non-PAT | PAT PAT |PCD ||PWT ||| WC 000 WB _PAGE_CACHE_MODE_WB WC | WC WC 001 WC _PAGE_CACHE_MODE_WC WC* | WC WC 010 UC- _PAGE_CACHE_MODE_UC_MINUS WC* | UC WC 011 UC _PAGE_CACHE_MODE_UC UC | UC ---------------------------------------------------------------------- (*) denotes implementation defined By default Linux today defaults both and ioremap_nocache() to use _PAGE_CACHE_MODE_UC_MINUS. On x86 ioremap() aliases ioremap_nocache(). The preferred value for Linux by may soon change however, the goal is to use _PAGE_CACHE_MODE_UC by default in the future. We can use ioremap_uc() to set PCD=1, PWT=1 on non-PAT systems and use a PAT value of UC for PAT systems. This will ensure the same settings are in place regardless of what Linux decides to use by default later and to not regress our MTRR strategy since the effective memory type will differ depending on the value used. Using a WC MTRR on such an area will be nullified. This technique can be used to protect the MMIO region in this driver's case and address the restrictions of the device's architecture as well as restrictions set upon us by powers of 2 when using MTRRs. This allows us to replace the two MTRR calls with a single 16 MiB WC MTRR and use page-attribute settings for non-PAT and PAT entry values for PAT systems to ensure the appropriate effective memory type won't have a write-combined effect on the MMIO region on both non-PAT and PAT systems. The framebuffer area will be sure to get the write-combined effective memory type by white-listing it with ioremap_wc(). We ensure the desired effective memory types are set by: 0) Using one ioremap_uc() for the MMIO region alone. This will set the page attribute settings for the MMIO region to PCD=1, PWT=1 for non-PAT systems while using a strong UC value on PAT systems. 1) Fixing the framebuffer ioremap'd area to exclude the MMIO region and using ioremap_wc() instead to whitelist the area we want for write-combining. On both cases an implementation defined (as per above table) effective memory type of WC is used for the framebuffer for non-PAT systems. [0] https://www-ssl.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-manual-325462.pdf Cc: Toshi Kani Cc: Suresh Siddha Cc: Ingo Molnar Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Juergen Gross Cc: Daniel Vetter Cc: Andy Lutomirski Cc: Dave Airlie Cc: Antonino Daplas Cc: Jean-Christophe Plagniol-Villard Cc: Tomi Valkeinen Cc: Ville Syrjälä Cc: Rob Clark Cc: Mathias Krause Cc: Andrzej Hajda Cc: Mel Gorman Cc: Vlastimil Babka Cc: Borislav Petkov Cc: Davidlohr Bueso Cc: linux-fbdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Luis R. Rodriguez --- drivers/video/fbdev/aty/atyfb.h | 1 - drivers/video/fbdev/aty/atyfb_base.c | 36 ++++++++++++++---------------------- 2 files changed, 14 insertions(+), 23 deletions(-) diff --git a/drivers/video/fbdev/aty/atyfb.h b/drivers/video/fbdev/aty/atyfb.h index 1f39a62..89ec439 100644 --- a/drivers/video/fbdev/aty/atyfb.h +++ b/drivers/video/fbdev/aty/atyfb.h @@ -184,7 +184,6 @@ struct atyfb_par { spinlock_t int_lock; #ifdef CONFIG_MTRR int mtrr_aper; - int mtrr_reg; #endif u32 mem_cntl; struct crtc saved_crtc; diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c index 8025624..546f5af 100644 --- a/drivers/video/fbdev/aty/atyfb_base.c +++ b/drivers/video/fbdev/aty/atyfb_base.c @@ -2630,21 +2630,13 @@ 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. */ + /* + * Only the ioremap_wc()'d area will get WC here + * since ioremap_uc() was used on the entire PCI BAR. + */ par->mtrr_aper = mtrr_add(par->res_start, par->res_size, MTRR_TYPE_WRCOMB, 1); - if (par->mtrr_aper >= 0 && !par->aux_start) { - /* Make a hole for mmio. */ - par->mtrr_reg = mtrr_add(par->res_start + 0x800000 - - GUI_RESERVE, GUI_RESERVE, - MTRR_TYPE_UNCACHABLE, 1); - if (par->mtrr_reg < 0) { - mtrr_del(par->mtrr_aper, 0, 0); - par->mtrr_aper = -1; - } - } } #endif @@ -2776,10 +2768,6 @@ aty_init_exit: par->pll_ops->set_pll(info, &par->saved_pll); #ifdef CONFIG_MTRR - if (par->mtrr_reg >= 0) { - mtrr_del(par->mtrr_reg, 0, 0); - par->mtrr_reg = -1; - } if (par->mtrr_aper >= 0) { mtrr_del(par->mtrr_aper, 0, 0); par->mtrr_aper = -1; @@ -3466,7 +3454,11 @@ static int atyfb_setup_generic(struct pci_dev *pdev, struct fb_info *info, } info->fix.mmio_start = raddr; - par->ati_regbase = ioremap(info->fix.mmio_start, 0x1000); + /* + * By using strong UC we force the MTRR to never have an + * effect on the MMIO region on both non-PAT and PAT systems. + */ + par->ati_regbase = ioremap_uc(info->fix.mmio_start, 0x1000); if (par->ati_regbase == NULL) return -ENOMEM; @@ -3491,7 +3483,10 @@ static int atyfb_setup_generic(struct pci_dev *pdev, struct fb_info *info, info->fix.smem_start = addr; info->fix.smem_len = 0x800000; - info->screen_base = ioremap(info->fix.smem_start, info->fix.smem_len); + aty_fudge_framebuffer_len(info); + + info->screen_base = ioremap_wc(info->fix.smem_start, + info->fix.smem_len); if (info->screen_base == NULL) { ret = -ENOMEM; goto atyfb_setup_generic_fail; @@ -3563,6 +3558,7 @@ static int atyfb_pci_probe(struct pci_dev *pdev, return -ENOMEM; } par = info->par; + par->bus_type = PCI; info->fix = atyfb_fix; info->device = &pdev->dev; par->pci_id = pdev->device; @@ -3732,10 +3728,6 @@ static void atyfb_remove(struct fb_info *info) #endif #ifdef CONFIG_MTRR - if (par->mtrr_reg >= 0) { - mtrr_del(par->mtrr_reg, 0, 0); - par->mtrr_reg = -1; - } if (par->mtrr_aper >= 0) { mtrr_del(par->mtrr_aper, 0, 0); par->mtrr_aper = -1; -- 2.3.2.209.gd67f9d5.dirty -- 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/