6.5-stable review patch. If anyone has any objections, please let me know.
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From: Icenowy Zheng uwu@icenowy.me
[ Upstream commit 278be83601dd1725d4732241f066d528e160a39d ]
Currently the code disables WUC only disables it for ioremap_wc(), which is only used when mapping writecombine pages like ioremap() (mapped to the kernel space). But for VRAM mapped in TTM/GEM, it is mapped with a crafted pgprot by the pgprot_writecombine() function, in which case WUC isn't disabled now.
Disable WUC for pgprot_writecombine() (fallback to SUC) if needed, like ioremap_wc().
This improves the AMDGPU driver's stability (solves some misrendering) on Loongson-3A5000/3A6000 machines.
Signed-off-by: Icenowy Zheng uwu@icenowy.me Signed-off-by: Huacai Chen chenhuacai@loongson.cn Signed-off-by: Sasha Levin sashal@kernel.org --- arch/loongarch/include/asm/io.h | 5 ++--- arch/loongarch/include/asm/pgtable-bits.h | 4 +++- arch/loongarch/kernel/setup.c | 10 +++++----- 3 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/arch/loongarch/include/asm/io.h b/arch/loongarch/include/asm/io.h index 1c94102200407..0355b64e90ed0 100644 --- a/arch/loongarch/include/asm/io.h +++ b/arch/loongarch/include/asm/io.h @@ -54,10 +54,9 @@ static inline void __iomem *ioremap_prot(phys_addr_t offset, unsigned long size, * @offset: bus address of the memory * @size: size of the resource to map */ -extern pgprot_t pgprot_wc; - #define ioremap_wc(offset, size) \ - ioremap_prot((offset), (size), pgprot_val(pgprot_wc)) + ioremap_prot((offset), (size), \ + pgprot_val(wc_enabled ? PAGE_KERNEL_WUC : PAGE_KERNEL_SUC))
#define ioremap_cache(offset, size) \ ioremap_prot((offset), (size), pgprot_val(PAGE_KERNEL)) diff --git a/arch/loongarch/include/asm/pgtable-bits.h b/arch/loongarch/include/asm/pgtable-bits.h index de46a6b1e9f11..7b9ac012cd090 100644 --- a/arch/loongarch/include/asm/pgtable-bits.h +++ b/arch/loongarch/include/asm/pgtable-bits.h @@ -105,13 +105,15 @@ static inline pgprot_t pgprot_noncached(pgprot_t _prot) return __pgprot(prot); }
+extern bool wc_enabled; + #define pgprot_writecombine pgprot_writecombine
static inline pgprot_t pgprot_writecombine(pgprot_t _prot) { unsigned long prot = pgprot_val(_prot);
- prot = (prot & ~_CACHE_MASK) | _CACHE_WUC; + prot = (prot & ~_CACHE_MASK) | (wc_enabled ? _CACHE_WUC : _CACHE_SUC);
return __pgprot(prot); } diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c index 9d830ab4e3025..1351614042d4e 100644 --- a/arch/loongarch/kernel/setup.c +++ b/arch/loongarch/kernel/setup.c @@ -161,19 +161,19 @@ static void __init smbios_parse(void) }
#ifdef CONFIG_ARCH_WRITECOMBINE -pgprot_t pgprot_wc = PAGE_KERNEL_WUC; +bool wc_enabled = true; #else -pgprot_t pgprot_wc = PAGE_KERNEL_SUC; +bool wc_enabled = false; #endif
-EXPORT_SYMBOL(pgprot_wc); +EXPORT_SYMBOL(wc_enabled);
static int __init setup_writecombine(char *p) { if (!strcmp(p, "on")) - pgprot_wc = PAGE_KERNEL_WUC; + wc_enabled = true; else if (!strcmp(p, "off")) - pgprot_wc = PAGE_KERNEL_SUC; + wc_enabled = false; else pr_warn("Unknown writecombine setting "%s".\n", p);