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Subject[PATCH 4.15 002/105] MIPS: ralink: Fix booting on MT7621
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neil@brown.name>

commit a63d706ea719190a79a6c769e898f70680044d3e upstream.

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

This commit 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 add a call to __sync().

Fixes: 3af5a67c86a3 ("MIPS: Fix early CM probing")
Signed-off-by: NeilBrown <neil@brown.name>
Reviewed-by: Matt Redfearn <matt.redfearn@mips.com>
Cc: John Crispin <john@phrozen.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.5+
Patchwork: https://patchwork.linux-mips.org/patch/18859/
Signed-off-by: James Hogan <jhogan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/mips/ralink/mt7621.c | 42 ++++++++++++++++++++++--------------------
1 file changed, 22 insertions(+), 20 deletions(-)

--- a/arch/mips/ralink/mt7621.c
+++ b/arch/mips/ralink/mt7621.c
@@ -170,6 +170,28 @@ void prom_soc_init(struct ralink_soc_inf
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_inf

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;

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