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From: James Hogan <james.hogan@imgtec.com>
To: Ralf Baechle <ralf@linux-mips.org>, <linux-mips@linux-mips.org>
Cc: <linux-kernel@vger.kernel.org>, James Hogan <james.hogan@imgtec.com>
Subject: [PATCH 6/9] MIPS: idle: Workaround wait + FDC problems
Date: Thu, 29 Jan 2015 11:14:11 +0000	[thread overview]
Message-ID: <1422530054-7976-7-git-send-email-james.hogan@imgtec.com> (raw)
In-Reply-To: <1422530054-7976-1-git-send-email-james.hogan@imgtec.com>

On certain cores (namely proAptiv and P5600) incoming data via a Fast
Debug Channel (FDC) while the core is blocked on a wait instruction will
cause the wait not to wake up even when another interrupt is received.
This makes an idle target stop as soon as you send FDC data to it, until
the debug probe interrupts it and restarts the wait instruction.

This is worked around by avoiding using r4k_wait on these cores if
CONFIG_MIPS_EJTAG_FDC_TTY is enabled (which would imply the user intends
to use the FDC).

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
---
 arch/mips/kernel/idle.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c
index 0b9082b6b683..3db277ea9e8d 100644
--- a/arch/mips/kernel/idle.c
+++ b/arch/mips/kernel/idle.c
@@ -176,6 +176,17 @@ void __init check_wait(void)
 		cpu_wait = rm7k_wait_irqoff;
 		break;
 
+	case CPU_PROAPTIV:
+	case CPU_P5600:
+		/*
+		 * Incoming Fast Debug Channel (FDC) data during a wait
+		 * instruction causes the wait never to resume, even if an
+		 * interrupt is received. Avoid using wait at all if FDC data is
+		 * likely to be received.
+		 */
+		if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY))
+			break;
+		/* fall through */
 	case CPU_M14KC:
 	case CPU_M14KEC:
 	case CPU_24K:
@@ -183,8 +194,6 @@ void __init check_wait(void)
 	case CPU_1004K:
 	case CPU_1074K:
 	case CPU_INTERAPTIV:
-	case CPU_PROAPTIV:
-	case CPU_P5600:
 	case CPU_M5150:
 		cpu_wait = r4k_wait;
 		if (read_c0_config7() & MIPS_CONF7_WII)
-- 
2.0.5


WARNING: multiple messages have this Message-ID (diff)
From: James Hogan <james.hogan@imgtec.com>
To: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org, James Hogan <james.hogan@imgtec.com>
Subject: [PATCH 6/9] MIPS: idle: Workaround wait + FDC problems
Date: Thu, 29 Jan 2015 11:14:11 +0000	[thread overview]
Message-ID: <1422530054-7976-7-git-send-email-james.hogan@imgtec.com> (raw)
Message-ID: <20150129111411.n-p_idkOXKHQhlfQK32K7whEXnXQjLXXNSWubFG7QEk@z> (raw)
In-Reply-To: <1422530054-7976-1-git-send-email-james.hogan@imgtec.com>

On certain cores (namely proAptiv and P5600) incoming data via a Fast
Debug Channel (FDC) while the core is blocked on a wait instruction will
cause the wait not to wake up even when another interrupt is received.
This makes an idle target stop as soon as you send FDC data to it, until
the debug probe interrupts it and restarts the wait instruction.

This is worked around by avoiding using r4k_wait on these cores if
CONFIG_MIPS_EJTAG_FDC_TTY is enabled (which would imply the user intends
to use the FDC).

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
---
 arch/mips/kernel/idle.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c
index 0b9082b6b683..3db277ea9e8d 100644
--- a/arch/mips/kernel/idle.c
+++ b/arch/mips/kernel/idle.c
@@ -176,6 +176,17 @@ void __init check_wait(void)
 		cpu_wait = rm7k_wait_irqoff;
 		break;
 
+	case CPU_PROAPTIV:
+	case CPU_P5600:
+		/*
+		 * Incoming Fast Debug Channel (FDC) data during a wait
+		 * instruction causes the wait never to resume, even if an
+		 * interrupt is received. Avoid using wait at all if FDC data is
+		 * likely to be received.
+		 */
+		if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY))
+			break;
+		/* fall through */
 	case CPU_M14KC:
 	case CPU_M14KEC:
 	case CPU_24K:
@@ -183,8 +194,6 @@ void __init check_wait(void)
 	case CPU_1004K:
 	case CPU_1074K:
 	case CPU_INTERAPTIV:
-	case CPU_PROAPTIV:
-	case CPU_P5600:
 	case CPU_M5150:
 		cpu_wait = r4k_wait;
 		if (read_c0_config7() & MIPS_CONF7_WII)
-- 
2.0.5

  parent reply	other threads:[~2015-01-29 11:16 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-29 11:14 [PATCH 0/9] Add MIPS EJTAG Fast Debug Channel TTY driver James Hogan
2015-01-29 11:14 ` James Hogan
2015-01-29 11:14 ` [PATCH 1/9] MIPS: Add architectural FDC IRQ fields James Hogan
2015-01-29 11:14   ` James Hogan
2015-01-29 11:14 ` [PATCH 2/9] MIPS: Read CPU IRQ line that FDC to routed to James Hogan
2015-01-29 11:14   ` James Hogan
2015-01-29 11:14 ` [PATCH 3/9] irqchip: mips-gic: Don't treat FDC IRQ as percpu devid James Hogan
2015-01-29 11:14   ` James Hogan
2015-01-29 11:14 ` [PATCH 4/9] irqchip: mips-gic: Add function for retrieving FDC IRQ James Hogan
2015-01-29 11:14   ` James Hogan
2015-01-29 11:14 ` [PATCH 5/9] MIPS: Malta: Implement get_c0_fdc_int() James Hogan
2015-01-29 11:14   ` James Hogan
2015-01-29 11:14 ` James Hogan [this message]
2015-01-29 11:14   ` [PATCH 6/9] MIPS: idle: Workaround wait + FDC problems James Hogan
2015-01-29 11:14 ` [PATCH 7/9] tty: Add MIPS EJTAG Fast Debug Channel TTY driver James Hogan
2015-01-29 11:14   ` James Hogan
2015-03-26 15:09   ` Greg Kroah-Hartman
2015-01-29 11:14 ` [PATCH 8/9] MIPS, ttyFDC: Add early FDC console support James Hogan
2015-01-29 11:14   ` James Hogan
2015-03-26 15:09   ` Greg Kroah-Hartman
2015-01-29 11:14 ` [PATCH 9/9] ttyFDC: Implement KGDB IO operations James Hogan
2015-01-29 11:14   ` James Hogan
2015-03-26 15:09   ` Greg Kroah-Hartman
2015-02-25 11:06 ` [PATCH 0/9] Add MIPS EJTAG Fast Debug Channel TTY driver James Hogan
2015-02-25 11:06   ` James Hogan

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