linux-kernel - [PATCH 06/10] MIPS: CPS: warn if a core doesn't start

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Date:	Tue, 22 Sep 2015 11:12:14 -0700
From:	Paul Burton <paul.burton@...tec.com>
To:	<linux-mips@...ux-mips.org>
CC:	Paul Burton <paul.burton@...tec.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Bresticker <abrestic@...omium.org>,
	<linux-kernel@...r.kernel.org>,
	Niklas Cassel <niklas.cassel@...s.com>,
	Ezequiel Garcia <ezequiel.garcia@...tec.com>,
	Markos Chandras <markos.chandras@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 06/10] MIPS: CPS: warn if a core doesn't start

When debugging core bringup it is useful to see the state of the CPC
sequencer, so output that value if the core hasn't started within a
reasonable amount of time (1 second). This avoids simply appearing to
the user to hang if a secondary core fails to start.

Signed-off-by: Paul Burton <paul.burton@...tec.com>
---

 arch/mips/kernel/smp-cps.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/smp-cps.c b/arch/mips/kernel/smp-cps.c
index 8b96750..48b1b75 100644
--- a/arch/mips/kernel/smp-cps.c
+++ b/arch/mips/kernel/smp-cps.c
@@ -8,6 +8,7 @@
  * option) any later version.
  */
 
+#include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/irqchip/mips-gic.h>
 #include <linux/sched.h>
@@ -188,7 +189,8 @@ err_out:
 
 static void boot_core(unsigned core)
 {
-	u32 access;
+	u32 access, stat, seq_state;
+	unsigned timeout;
 
 	/* Select the appropriate core */
 	write_gcr_cl_other(core << CM_GCR_Cx_OTHER_CORENUM_SHF);
@@ -208,6 +210,28 @@ static void boot_core(unsigned core)
 		/* Reset the core */
 		mips_cpc_lock_other(core);
 		write_cpc_co_cmd(CPC_Cx_CMD_RESET);
+
+		timeout = 100;
+		while (true) {
+			stat = read_cpc_co_stat_conf();
+			seq_state = stat & CPC_Cx_STAT_CONF_SEQSTATE_MSK;
+
+			/* U6 == coherent execution, ie. the core is up */
+			if (seq_state == CPC_Cx_STAT_CONF_SEQSTATE_U6)
+				break;
+
+			/* Delay a little while before we start warning */
+			if (timeout) {
+				timeout--;
+				mdelay(10);
+				continue;
+			}
+
+			pr_warn("Waiting for core %u to start... STAT_CONF=0x%x\n",
+				core, stat);
+			mdelay(1000);
+		}
+
 		mips_cpc_unlock_other();
 	} else {
 		/* Take the core out of reset */
-- 
2.5.3

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