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: Icenowy Zheng <uwu@icenowy.me>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 5 insertions, 5 deletions

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 7783f0a3d742..aed65915e932 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);