linux-kernel - [PATCH v3] MIPS: ralink: fix booting on mt7621

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Date:   Wed, 21 Mar 2018 14:02:10 +1100
From:   NeilBrown <neil@...wn.name>
To:     John Crispin <john@...ozen.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>
Cc:     linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] MIPS: ralink: fix booting on mt7621


Since commit 3af5a67c86a3 ("MIPS: Fix early CM probing") the MT7621
has not been able to boot.

This patched caused mips_cm_probe() to be called before
mt7621.c::proc_soc_init().

prom_soc_init() has a comment explaining that mips_cm_probe()
"wipes out the bootloader config" and means that configuration
registers are no longer available.  It has some code to re-enable
this config.

Before this re-enable code is run, the sysc register cannot be
read, so when SYSC_REG_CHIP_NAME0 is read, a garbage value
is returned and panic() is called.

If we move the config-repair code to the top of prom_soc_init(),
the registers can be read and boot can proceed.

Very occasionally, the first register read after the reconfiguration
returns garbage.  So I added a call to __sync().

Fixes: 3af5a67c86a3 ("MIPS: Fix early CM probing")
Signed-off-by: NeilBrown <neil@...wn.name>
---
 arch/mips/ralink/mt7621.c | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/arch/mips/ralink/mt7621.c b/arch/mips/ralink/mt7621.c
index 1b274742077d..d2718de60b9b 100644
--- a/arch/mips/ralink/mt7621.c
+++ b/arch/mips/ralink/mt7621.c
@@ -170,6 +170,28 @@ void prom_soc_init(struct ralink_soc_info *soc_info)
 	u32 n1;
 	u32 rev;
 
+	/* Early detection of CMP support */
+	mips_cm_probe();
+	mips_cpc_probe();
+
+	if (mips_cps_numiocu(0)) {
+		/*
+		 * mips_cm_probe() wipes out bootloader
+		 * config for CM regions and we have to configure them
+		 * again. This SoC cannot talk to pamlbus devices
+		 * witout proper iocu region set up.
+		 *
+		 * FIXME: it would be better to do this with values
+		 * from DT, but we need this very early because
+		 * without this we cannot talk to pretty much anything
+		 * including serial.
+		 */
+		write_gcr_reg0_base(MT7621_PALMBUS_BASE);
+		write_gcr_reg0_mask(~MT7621_PALMBUS_SIZE |
+				    CM_GCR_REGn_MASK_CMTGT_IOCU0);
+		__sync();
+	}
+
 	n0 = __raw_readl(sysc + SYSC_REG_CHIP_NAME0);
 	n1 = __raw_readl(sysc + SYSC_REG_CHIP_NAME1);
 
@@ -194,26 +216,6 @@ void prom_soc_init(struct ralink_soc_info *soc_info)
 
 	rt2880_pinmux_data = mt7621_pinmux_data;
 
-	/* Early detection of CMP support */
-	mips_cm_probe();
-	mips_cpc_probe();
-
-	if (mips_cps_numiocu(0)) {
-		/*
-		 * mips_cm_probe() wipes out bootloader
-		 * config for CM regions and we have to configure them
-		 * again. This SoC cannot talk to pamlbus devices
-		 * witout proper iocu region set up.
-		 *
-		 * FIXME: it would be better to do this with values
-		 * from DT, but we need this very early because
-		 * without this we cannot talk to pretty much anything
-		 * including serial.
-		 */
-		write_gcr_reg0_base(MT7621_PALMBUS_BASE);
-		write_gcr_reg0_mask(~MT7621_PALMBUS_SIZE |
-				    CM_GCR_REGn_MASK_CMTGT_IOCU0);
-	}
 
 	if (!register_cps_smp_ops())
 		return;
-- 
2.14.0.rc0.dirty


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