From 385db982b277a1eb5998b6316a500a2d6d9592b1 Mon Sep 17 00:00:00 2001 From: Rodrigo Vivi Date: Tue, 29 Aug 2017 16:09:07 -0700 Subject: [PATCH] drm/i915/cnl: Avoid ioremap_wc on Cannonlake as well. Mime-version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8bit Git-commit: 385db982b277a1eb5998b6316a500a2d6d9592b1 Patch-mainline: v4.15-rc1 References: FATE#322643 bsc#1055900 Driver’s CPU access to GTT is via the GTTMMADR BAR. The current HW implementation of that BAR is to only support <= DW (and maybe QW) writes—not 16/32/64B writes that could occur with WC and/or SSE/AVX moves. GTTMMADR must be marked uncacheable (UC). Accesses to GTTMMADR(GTT), must be 64 bits or less (ie. 1 GTT entry). V2: Get clarification on the reasons and spec is getting updated to reflect it now. Cc: Joonas Lahtinen Suggested-by: Ben Widawsky Signed-off-by: Rodrigo Vivi Reviewed-by: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20170829230907.21363-1-rodrigo.vivi@intel.com Acked-by: Takashi Iwai --- drivers/gpu/drm/i915/i915_gem_gtt.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -2783,13 +2783,13 @@ static int ggtt_probe_common(struct i915 phys_addr = pci_resource_start(pdev, 0) + pci_resource_len(pdev, 0) / 2; /* - * On BXT writes larger than 64 bit to the GTT pagetable range will be - * dropped. For WC mappings in general we have 64 byte burst writes - * when the WC buffer is flushed, so we can't use it, but have to + * On BXT+/CNL+ writes larger than 64 bit to the GTT pagetable range + * will be dropped. For WC mappings in general we have 64 byte burst + * writes when the WC buffer is flushed, so we can't use it, but have to * resort to an uncached mapping. The WC issue is easily caught by the * readback check when writing GTT PTE entries. */ - if (IS_GEN9_LP(dev_priv)) + if (IS_GEN9_LP(dev_priv) || INTEL_GEN(dev_priv) >= 10) ggtt->gsm = ioremap_nocache(phys_addr, size); else ggtt->gsm = ioremap_wc(phys_addr, size);