[PATCH] MIPS: clean up CONFIG_MIPS_PGD_CONTEXT handling

From: Huang Pei <huangpei@loongson.cn>
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>, ambrosehua@gmail.com
Cc: Bibo Mao <maobibo@loongson.cn>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mips@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-mm@kvack.org, Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Paul Burton <paulburton@kernel.org>,
	Li Xuefeng <lixuefeng@loongson.cn>,
	Yang Tiezhu <yangtiezhu@loongson.cn>,
	Gao Juxin <gaojuxin@loongson.cn>,
	Fuxin Zhang <zhangfx@lemote.com>, Huacai Chen <chenhc@lemote.com>
Subject: [PATCH] MIPS: clean up CONFIG_MIPS_PGD_CONTEXT handling
Date: Sat, 20 Feb 2021 14:51:00 +0800	[thread overview]
Message-ID: <20210220065100.10950-1-huangpei@loongson.cn> (raw)

CP0 Context has enough room for wraping pgd into its 41-bit PTEBase field.

+. For XPHYS, the trick is that pgd is 4kB aligned, and the PABITS <= 48,
only save 48 - 12 + 5(for bit[63:59]) = 41 bit, aka. :

   bit[63:59] | 0000 0000 000 |  bit[47:12] | 0000 0000 0000

+. for CKSEG0, only save 29 - 12 = 17 bit

+. use CAC_BASE for accessing bit[63:59] of pgd

Signed-off-by: Huang Pei <huangpei@loongson.cn>
---
 arch/mips/mm/tlbex.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index a7521b8f7658..c9a948defac8 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -848,8 +848,8 @@ void build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
 		/* Clear lower 23 bits of context. */
 		uasm_i_dins(p, ptr, 0, 0, 23);
 
-		/* 1 0	1 0 1  << 6  xkphys cached */
-		uasm_i_ori(p, ptr, ptr, 0x540);
+		/* insert bit[63:59] of CAC_BASE into bit[11:6] of ptr */
+		uasm_i_ori(p, ptr, ptr, (CAC_BASE >> 53));
 		uasm_i_drotr(p, ptr, ptr, 11);
 #elif defined(CONFIG_SMP)
 		UASM_i_CPUID_MFC0(p, ptr, SMP_CPUID_REG);
@@ -1164,8 +1164,8 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 
 	if (pgd_reg == -1) {
 		vmalloc_branch_delay_filled = 1;
-		/* 1 0	1 0 1  << 6  xkphys cached */
-		uasm_i_ori(p, ptr, ptr, 0x540);
+		/* insert bit[63:59] of CAC_BASE into bit[11:6] of ptr */
+		uasm_i_ori(p, ptr, ptr, (CAC_BASE >> 53));
 		uasm_i_drotr(p, ptr, ptr, 11);
 	}
 
-- 
2.17.1


