From 3cc2dac5be3f23414a4efdee0b26d79bed297cac Mon Sep 17 00:00:00 2001 From: "Luis R. Rodriguez" Date: Thu, 9 Jul 2015 18:24:58 -0700 Subject: [PATCH] drivers/video/fbdev/atyfb: Replace MTRR UC hole with strong UC MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 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 enough MTRRs to cover the framebuffer. The current 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 mmapped 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. See also: 2f9e897353fc ("x86/mm/mtrr, pat: Document Write Combining MTRR type effects on PAT / non-PAT pages") By default, Linux today defaults both pci_mmap_page_range() and ioremap_nocache() to use _PAGE_CACHE_MODE_UC_MINUS. On x86, ioremap() aliases ioremap_nocache(). The preferred value for Linux 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-combining 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 ioremapped area to exclude the MMIO region and using ioremap_wc() instead to whitelist the area we want for write-combining. In both cases, an implementation defined (as per 2f9e897353fc) effective memory type of WC is used for the framebuffer for non-PAT systems. Signed-off-by: Luis R. Rodriguez Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andrzej Hajda Cc: Andy Lutomirski Cc: Antonino Daplas Cc: Daniel Vetter Cc: Dave Airlie Cc: Davidlohr Bueso Cc: H. Peter Anvin Cc: Jean-Christophe Plagniol-Villard Cc: Juergen Gross Cc: Linus Torvalds Cc: Mathias Krause Cc: Mel Gorman Cc: Peter Zijlstra Cc: Rob Clark Cc: Suresh Siddha Cc: Thomas Gleixner Cc: Tomi Valkeinen Cc: Toshi Kani Cc: Ville Syrjälä Cc: Vlastimil Babka Cc: arnd@arndb.de Cc: benh@kernel.crashing.org Cc: dan.j.williams@intel.com Cc: geert@linux-m68k.org Cc: hch@lst.de Cc: hmh@hmh.eng.br Cc: linux-fbdev@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-pci@vger.kernel.org Cc: mpe@ellerman.id.au Cc: mst@redhat.com Cc: ralf@linux-mips.org Cc: ross.zwisler@linux.intel.com Cc: stefan.bader@canonical.com Cc: tj@kernel.org Cc: ville.syrjala@linux.intel.com Link: http://lkml.kernel.org/r/1435196060-27350-3-git-send-email-mcgrof@do-not-panic.com Link: http://lkml.kernel.org/r/1436491499-3289-4-git-send-email-mcgrof@do-not-panic.com Signed-off-by: Ingo Molnar --- 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 1f39a62f899b..89ec4398d201 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 de8f7e082c87..7770a8485fb5 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; @@ -3503,7 +3495,10 @@ static int atyfb_setup_generic(struct pci_dev *pdev, struct fb_info *info, */ 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; @@ -3575,6 +3570,7 @@ 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; @@ -3744,10 +3740,6 @@ 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; -- 2.20.1