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LoongArch: Disable WUC for pgprot_writecombine() like ioremap_wc()

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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>
This commit is contained in:
Icenowy Zheng 2023-10-18 08:42:52 +08:00 • committed by Huacai Chen
parent 477a0ebec1
commit 278be83601
3 changed files with 10 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
arch/loongarch/include/asm/io.h
View file

@ -52,10 +52,9 @@ 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))

4
arch/loongarch/include/asm/pgtable-bits.h
View file

@ -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);
}

10
arch/loongarch/kernel/setup.c
View file

@ -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);