linux-kernel - [PATCH] MIPS: BMIPS: Disable pref 30 for buggy CPUs

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Message-Id: <20200731042401.22871-1-f.fainelli@gmail.com>
Date:   Thu, 30 Jul 2020 21:24:01 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-mips@...ux-mips.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        bcm-kernel-feedback-list@...adcom.com (open list:BROADCOM BMIPS MIPS
        ARCHITECTURE),
        linux-mips@...r.kernel.org (open list:BROADCOM BMIPS MIPS ARCHITECTURE),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] MIPS: BMIPS: Disable pref 30 for buggy CPUs

Disable pref 30 by utilizing the standard quirk method and matching the
affected SoCs: 7344, 7346, 7425.

Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 arch/mips/bmips/setup.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index 19308df5f577..df0efea12611 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -110,6 +110,20 @@ static void bcm6368_quirks(void)
 	bcm63xx_fixup_cpu1();
 }
 
+static void bmips5000_pref30_quirk(void)
+{
+	__asm__ __volatile__(
+	"	li	$8, 0x5a455048\n"
+	"	.word	0x4088b00f\n"	/* mtc0 $8, $22, 15 */
+	"	nop; nop; nop\n"
+	"	.word	0x4008b008\n"	/* mfc0 $8, $22, 8 */
+	/* disable "pref 30" on buggy CPUs */
+	"	lui	$9, 0x0800\n"
+	"	or	$8, $9\n"
+	"	.word	0x4088b008\n"	/* mtc0 $8, $22, 8 */
+	: : : "$8", "$9");
+}
+
 static const struct bmips_quirk bmips_quirk_list[] = {
 	{ "brcm,bcm3368",		&bcm6358_quirks			},
 	{ "brcm,bcm3384-viper",		&bcm3384_viper_quirks		},
@@ -120,6 +134,9 @@ static const struct bmips_quirk bmips_quirk_list[] = {
 	{ "brcm,bcm6368",		&bcm6368_quirks			},
 	{ "brcm,bcm63168",		&bcm6368_quirks			},
 	{ "brcm,bcm63268",		&bcm6368_quirks			},
+	{ "brcm,bcm7344",		&bmips5000_pref30_quirk		},
+	{ "brcm,bcm7346",		&bmips5000_pref30_quirk		},
+	{ "brcm,bcm7425",		&bmips5000_pref30_quirk		},
 	{ },
 };
 
-- 
2.25.1