Commit 278be836 authored by Icenowy Zheng's avatar Icenowy Zheng Committed by Huacai Chen
Browse files

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



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: default avatarIcenowy Zheng <uwu@icenowy.me>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 477a0ebe

arch/loongarch/include/asm/io.h

+2 −3
Original line number Diff line number Diff line
@@ -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))

arch/loongarch/include/asm/pgtable-bits.h

+3 −1
Original line number Diff line number Diff line
@@ -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);

}

arch/loongarch/kernel/setup.c

+5 −5
Original line number Diff line number Diff line
@@ -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);