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From:   Zhou Yanjie <zhouyanjie@zoho.com>
To:     linux-mips@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, ralf@linux-mips.org,
        paulburton@kernel.org, jhogan@kernel.org, paul@crapouillou.net,
        jiaxun.yang@flygoat.com, gregkh@linuxfoundation.org,
        malat@debian.org, tglx@linutronix.de, chenhc@lemote.com
Subject: [PATCH 2/2 v3] MIPS: Ingenic: Disable abandoned HPTLB function.
Date:   Tue, 19 Nov 2019 22:28:47 +0800
Message-Id: <1574173727-123321-3-git-send-email-zhouyanjie@zoho.com>
In-Reply-To: <1574173727-123321-1-git-send-email-zhouyanjie@zoho.com>
References: <1571909341-10108-1-git-send-email-zhouyanjie@zoho.com>
 <1574173727-123321-1-git-send-email-zhouyanjie@zoho.com>
Sender: linux-kernel-owner@vger.kernel.org
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JZ4760/JZ4770/JZ4775/X1000/X1500 has an abandoned huge page tlb,
this mode is not compatible with the MIPS standard, it will cause
tlbmiss and into an infinite loop (line 21 in the tlb-funcs.S)
when starting the init process. write 0xa9000000 to cp0 register 5
sel 4 to disable this function to prevent getting stuck. Confirmed
by Ingenic, this operation will not adversely affect processors
without HPTLB function.

Signed-off-by: Zhou Yanjie <zhouyanjie@zoho.com>
---
 arch/mips/include/asm/mipsregs.h |  6 ++++++
 arch/mips/kernel/cpu-probe.c     | 21 +++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index bdbdc19..0d5a309 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -689,6 +689,9 @@
 #define MIPS_CONF7_IAR		(_ULCAST_(1) << 10)
 #define MIPS_CONF7_AR		(_ULCAST_(1) << 16)
 
+/* Ingenic HPTLB off bits */
+#define XBURST_PAGECTRL_HPTLB_DIS 0xa9000000
+
 /* Ingenic Config7 bits */
 #define MIPS_CONF7_BTB_LOOP_EN	(_ULCAST_(1) << 4)
 
@@ -1971,6 +1974,9 @@ do {									\
 #define read_c0_brcm_sleepcount()	__read_32bit_c0_register($22, 7)
 #define write_c0_brcm_sleepcount(val)	__write_32bit_c0_register($22, 7, val)
 
+/* Ingenic page ctrl register */
+#define write_c0_page_ctrl(val)	__write_32bit_c0_register($5, 4, val)
+
 /*
  * Macros to access the guest system control coprocessor
  */
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 7a0e33c..3b5f4fb 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -1965,13 +1965,30 @@ static inline void cpu_probe_ingenic(struct cpuinfo_mips *c, unsigned int cpu)
 		break;
 	}
 
+	switch (c->processor_id & PRID_COMP_MASK) {
+	/*
+	 * The config0 register in the XBurst CPUs with a processor ID of
+	 * PRID_COMP_INGENIC_D1 has an abandoned huge page tlb mode, this
+	 * mode is not compatible with the MIPS standard, it will cause
+	 * tlbmiss and into an infinite loop (line 21 in the tlb-funcs.S)
+	 * when starting the init process. After chip reset, the default
+	 * is HPTLB mode, Write 0xa9000000 to cp0 register 5 sel 4 to
+	 * switch back to VTLB mode to prevent getting stuck.
+	 */
+	case PRID_COMP_INGENIC_D1:
+		write_c0_page_ctrl(XBURST_PAGECTRL_HPTLB_DIS);
+		break;
 	/*
-	 * The config0 register in the Xburst CPUs with a processor ID of
+	 * The config0 register in the XBurst CPUs with a processor ID of
 	 * PRID_COMP_INGENIC_D0 report themselves as MIPS32r2 compatible,
 	 * but they don't actually support this ISA.
 	 */
-	if ((c->processor_id & PRID_COMP_MASK) == PRID_COMP_INGENIC_D0)
+	case PRID_COMP_INGENIC_D0:
 		c->isa_level &= ~MIPS_CPU_ISA_M32R2;
+		break;
+	default:
+		break;
+	}
 }
 
 static inline void cpu_probe_netlogic(struct cpuinfo_mips *c, int cpu)
-- 
2.7.4