[PATCH AUTOSEL 4.9 18/25] MIPS: perf: ath79: Fix perfcount IRQ assignment

[PATCH AUTOSEL 4.9 18/25] MIPS: perf: ath79: Fix perfcount IRQ assignment

[Sasha Levin]

From: Petr Štetiar <ynezz@true.cz>

[ Upstream commit a1e8783db8e0d58891681bc1e6d9ada66eae8e20 ]

Currently it's not possible to use perf on ath79 due to genirq flags
mismatch happening on static virtual IRQ 13 which is used for
performance counters hardware IRQ 5.

On TP-Link Archer C7v5:

           CPU0
  2:          0      MIPS   2  ath9k
  4:        318      MIPS   4  19000000.eth
  7:      55034      MIPS   7  timer
  8:       1236      MISC   3  ttyS0
 12:          0      INTC   1  ehci_hcd:usb1
 13:          0  gpio-ath79   2  keys
 14:          0  gpio-ath79   5  keys
 15:         31  AR724X PCI    1  ath10k_pci

 $ perf top
 genirq: Flags mismatch irq 13. 00014c83 (mips_perf_pmu) vs. 00002003 (keys)

On TP-Link Archer C7v4:

         CPU0
  4:          0      MIPS   4  19000000.eth
  5:       7135      MIPS   5  1a000000.eth
  7:      98379      MIPS   7  timer
  8:         30      MISC   3  ttyS0
 12:      90028      INTC   0  ath9k
 13:       5520      INTC   1  ehci_hcd:usb1
 14:       4623      INTC   2  ehci_hcd:usb2
 15:      32844  AR724X PCI    1  ath10k_pci
 16:          0  gpio-ath79  16  keys
 23:          0  gpio-ath79  23  keys

 $ perf top
 genirq: Flags mismatch irq 13. 00014c80 (mips_perf_pmu) vs. 00000080 (ehci_hcd:usb1)

This problem is happening, because currently statically assigned virtual
IRQ 13 for performance counters is not claimed during the initialization
of MIPS PMU during the bootup, so the IRQ subsystem doesn't know, that
this interrupt isn't available for further use.

So this patch fixes the issue by simply booking hardware IRQ 5 for MIPS PMU.

Tested-by: Kevin 'ldir' Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Acked-by: John Crispin <john@phrozen.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/mips/ath79/setup.c          |  6 ------
 drivers/irqchip/irq-ath79-misc.c | 11 +++++++++++
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/mips/ath79/setup.c b/arch/mips/ath79/setup.c
index 26a058d58d37..c7c31e214813 100644
--- a/arch/mips/ath79/setup.c
+++ b/arch/mips/ath79/setup.c
@@ -183,12 +183,6 @@ const char *get_system_type(void)
 	return ath79_sys_type;
 }
 
-int get_c0_perfcount_int(void)
-{
-	return ATH79_MISC_IRQ(5);
-}
-EXPORT_SYMBOL_GPL(get_c0_perfcount_int);
-
 unsigned int get_c0_compare_int(void)
 {
 	return CP0_LEGACY_COMPARE_IRQ;
diff --git a/drivers/irqchip/irq-ath79-misc.c b/drivers/irqchip/irq-ath79-misc.c
index aa7290784636..0390603170b4 100644
--- a/drivers/irqchip/irq-ath79-misc.c
+++ b/drivers/irqchip/irq-ath79-misc.c
@@ -22,6 +22,15 @@
 #define AR71XX_RESET_REG_MISC_INT_ENABLE	4
 
 #define ATH79_MISC_IRQ_COUNT			32
+#define ATH79_MISC_PERF_IRQ			5
+
+static int ath79_perfcount_irq;
+
+int get_c0_perfcount_int(void)
+{
+	return ath79_perfcount_irq;
+}
+EXPORT_SYMBOL_GPL(get_c0_perfcount_int);
 
 static void ath79_misc_irq_handler(struct irq_desc *desc)
 {
@@ -113,6 +122,8 @@ static void __init ath79_misc_intc_domain_init(
 {
 	void __iomem *base = domain->host_data;
 
+	ath79_perfcount_irq = irq_create_mapping(domain, ATH79_MISC_PERF_IRQ);
+
 	/* Disable and clear all interrupts */
 	__raw_writel(0, base + AR71XX_RESET_REG_MISC_INT_ENABLE);
 	__raw_writel(0, base + AR71XX_RESET_REG_MISC_INT_STATUS);
-- 
2.20.1

Re: [PATCH AUTOSEL 4.9 18/25] MIPS: perf: ath79: Fix perfcount IRQ assignment

[Petr Štetiar]

Hi,

Karl has reported to me today, that he's experiencing weird reboot hang on his
devices with 4.9.180 kernel and that he has bisected it down to my backported
patch.

I would like to kindly ask you for removal of this patch.  This patch should
be reverted from all stable kernels up to 5.1, because perf counters were not
broken on those kernels, and this patch won't work on the ath79 legacy IRQ
code anyway, it needs new irqchip driver which was enabled on ath79 with
commit 51fa4f8912c0 ("MIPS: ath79: drop legacy IRQ code").

Thanks!

Cheers,

Petr

Re: [PATCH AUTOSEL 4.9 18/25] MIPS: perf: ath79: Fix perfcount IRQ assignment

[Greg KH]

On Thu, Jun 06, 2019 at 11:28:04PM +0200, Petr Štetiar wrote:
> Hi,
> 
> Karl has reported to me today, that he's experiencing weird reboot hang on his
> devices with 4.9.180 kernel and that he has bisected it down to my backported
> patch.
> 
> I would like to kindly ask you for removal of this patch.  This patch should
> be reverted from all stable kernels up to 5.1, because perf counters were not
> broken on those kernels, and this patch won't work on the ath79 legacy IRQ
> code anyway, it needs new irqchip driver which was enabled on ath79 with
> commit 51fa4f8912c0 ("MIPS: ath79: drop legacy IRQ code").

Thanks for the report, I'll go revert this from everywhere.

greg k-h