[PATCH v2 0/2] Tegra30+ CPU suspend-resume bug-fixes

[PATCH v2 0/2] Tegra30+ CPU suspend-resume bug-fixes

[Dmitry Osipenko]

Hello,

This small series addresses two suspend-resume bugs: one affects Tegra30+
due to a typo in the code, other fixes CPU hang on Tegra30 specifically.

Changelog:

v2: Reworded comment to the code to make it sound better in the patch
    "Use WFE for power-gating on Tegra30".

Dmitry Osipenko (2):
  ARM: tegra: Fix FLOW_CTLR_HALT register clobbering by tegra_resume()
  ARM: tegra: Use WFE for power-gating on Tegra30

 arch/arm/mach-tegra/reset-handler.S |  6 +++---
 arch/arm/mach-tegra/sleep-tegra30.S |  4 +++-
 drivers/soc/tegra/flowctrl.c        | 19 +++++++++++++++++--
 3 files changed, 23 insertions(+), 6 deletions(-)

-- 
2.22.0

[PATCH v2 1/2] ARM: tegra: Fix FLOW_CTLR_HALT register clobbering by tegra_resume()

[Dmitry Osipenko]

There is an unfortunate typo in the code that results in writing to
FLOW_CTLR_HALT instead of FLOW_CTLR_CSR.

Cc: <stable@vger.kernel.org>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 arch/arm/mach-tegra/reset-handler.S | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-tegra/reset-handler.S b/arch/arm/mach-tegra/reset-handler.S
index df44828a34d3..53123ae4ac3b 100644
--- a/arch/arm/mach-tegra/reset-handler.S
+++ b/arch/arm/mach-tegra/reset-handler.S
@@ -44,16 +44,16 @@ ENTRY(tegra_resume)
 	cmp	r6, #TEGRA20
 	beq	1f				@ Yes
 	/* Clear the flow controller flags for this CPU. */
-	cpu_to_csr_reg r1, r0
+	cpu_to_csr_reg r3, r0
 	mov32	r2, TEGRA_FLOW_CTRL_BASE
-	ldr	r1, [r2, r1]
+	ldr	r1, [r2, r3]
 	/* Clear event & intr flag */
 	orr	r1, r1, \
 		#FLOW_CTRL_CSR_INTR_FLAG | FLOW_CTRL_CSR_EVENT_FLAG
 	movw	r0, #0x3FFD	@ enable, cluster_switch, immed, bitmaps
 				@ & ext flags for CPU power mgnt
 	bic	r1, r1, r0
-	str	r1, [r2]
+	str	r1, [r2, r3]
 1:
 
 	mov32	r9, 0xc09
-- 
2.22.0

[PATCH v2 2/2] ARM: tegra: Use WFE for power-gating on Tegra30

[Dmitry Osipenko]

Turned out that WFI doesn't work reliably on Tegra30 as a trigger for
the power-gating, it causes CPU hang under some circumstances like having
memory controller running of PLLP. The TRM doc states that WFI should be
used for the Big-Little "Cluster Switch", while WFE for the power-gating.
Hence let's use the WFE for CPU0 power-gating, like it is done for the
power-gating of a secondary cores. This fixes CPU hang after entering LP2
with memory running off PLLP.

Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 arch/arm/mach-tegra/sleep-tegra30.S |  4 +++-
 drivers/soc/tegra/flowctrl.c        | 19 +++++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
index 6c28395d8c75..17f7a2a6a494 100644
--- a/arch/arm/mach-tegra/sleep-tegra30.S
+++ b/arch/arm/mach-tegra/sleep-tegra30.S
@@ -683,10 +683,12 @@ tegra30_enter_sleep:
 	dsb
 	ldr	r0, [r6, r2] /* memory barrier */
 
+	cmp	r10, #TEGRA30
 halted:
 	isb
 	dsb
-	wfi	/* CPU should be power gated here */
+	wfine	/* CPU should be power gated here */
+	wfeeq
 
 	/* !!!FIXME!!! Implement halt failure handler */
 	b	halted
diff --git a/drivers/soc/tegra/flowctrl.c b/drivers/soc/tegra/flowctrl.c
index b6bdeef33db1..eb96a3086d6d 100644
--- a/drivers/soc/tegra/flowctrl.c
+++ b/drivers/soc/tegra/flowctrl.c
@@ -91,8 +91,23 @@ void flowctrl_cpu_suspend_enter(unsigned int cpuid)
 		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP;
 		/* clear wfi bitmap */
 		reg &= ~TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP;
-		/* pwr gating on wfi */
-		reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
+
+		if (tegra_get_chip_id() == TEGRA30) {
+			/*
+			 * The wfi doesn't work well on Tegra30 because
+			 * CPU hangs under some odd circumstances after
+			 * power-gating (like memory running off PLLP),
+			 * hence use wfe that is working perfectly fine.
+			 * Note that Tegra30 TRM doc clearly stands that
+			 * wfi should be used for the "Cluster Switching",
+			 * while wfe for the power-gating, just like it
+			 * is done on Tegra20.
+			 */
+			reg |= TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 << cpuid;
+		} else {
+			/* pwr gating on wfi */
+			reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
+		}
 		break;
 	}
 	reg |= FLOW_CTRL_CSR_INTR_FLAG;			/* clear intr flag */
-- 
2.22.0

Re: [PATCH v2 2/2] ARM: tegra: Use WFE for power-gating on Tegra30

[Peter Geis]

The Ouya (tegra30) hard locks when the emc clock drops below 400mhz.
Discovered while testing the devfreq and emc drivers.
This patch resolves that issue.

Tested-by: Peter Geis <pgwipeout@gmail.com>

On Tue, Jul 30, 2019 at 2:10 PM Dmitry Osipenko <digetx@gmail.com> wrote:
>
> Turned out that WFI doesn't work reliably on Tegra30 as a trigger for
> the power-gating, it causes CPU hang under some circumstances like having
> memory controller running of PLLP. The TRM doc states that WFI should be
> used for the Big-Little "Cluster Switch", while WFE for the power-gating.
> Hence let's use the WFE for CPU0 power-gating, like it is done for the
> power-gating of a secondary cores. This fixes CPU hang after entering LP2
> with memory running off PLLP.
>
> Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  arch/arm/mach-tegra/sleep-tegra30.S |  4 +++-
>  drivers/soc/tegra/flowctrl.c        | 19 +++++++++++++++++--
>  2 files changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
> index 6c28395d8c75..17f7a2a6a494 100644
> --- a/arch/arm/mach-tegra/sleep-tegra30.S
> +++ b/arch/arm/mach-tegra/sleep-tegra30.S
> @@ -683,10 +683,12 @@ tegra30_enter_sleep:
>         dsb
>         ldr     r0, [r6, r2] /* memory barrier */
>
> +       cmp     r10, #TEGRA30
>  halted:
>         isb
>         dsb
> -       wfi     /* CPU should be power gated here */
> +       wfine   /* CPU should be power gated here */
> +       wfeeq
>
>         /* !!!FIXME!!! Implement halt failure handler */
>         b       halted
> diff --git a/drivers/soc/tegra/flowctrl.c b/drivers/soc/tegra/flowctrl.c
> index b6bdeef33db1..eb96a3086d6d 100644
> --- a/drivers/soc/tegra/flowctrl.c
> +++ b/drivers/soc/tegra/flowctrl.c
> @@ -91,8 +91,23 @@ void flowctrl_cpu_suspend_enter(unsigned int cpuid)
>                 reg &= ~TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP;
>                 /* clear wfi bitmap */
>                 reg &= ~TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP;
> -               /* pwr gating on wfi */
> -               reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
> +
> +               if (tegra_get_chip_id() == TEGRA30) {
> +                       /*
> +                        * The wfi doesn't work well on Tegra30 because
> +                        * CPU hangs under some odd circumstances after
> +                        * power-gating (like memory running off PLLP),
> +                        * hence use wfe that is working perfectly fine.
> +                        * Note that Tegra30 TRM doc clearly stands that
> +                        * wfi should be used for the "Cluster Switching",
> +                        * while wfe for the power-gating, just like it
> +                        * is done on Tegra20.
> +                        */
> +                       reg |= TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 << cpuid;
> +               } else {
> +                       /* pwr gating on wfi */
> +                       reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
> +               }
>                 break;
>         }
>         reg |= FLOW_CTRL_CSR_INTR_FLAG;                 /* clear intr flag */
> --
> 2.22.0
>

Re: [PATCH v2 0/2] Tegra30+ CPU suspend-resume bug-fixes

[Thierry Reding]

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On Tue, Jul 30, 2019 at 08:23:38PM +0300, Dmitry Osipenko wrote:
> Hello,
> 
> This small series addresses two suspend-resume bugs: one affects Tegra30+
> due to a typo in the code, other fixes CPU hang on Tegra30 specifically.
> 
> Changelog:
> 
> v2: Reworded comment to the code to make it sound better in the patch
>     "Use WFE for power-gating on Tegra30".
> 
> Dmitry Osipenko (2):
>   ARM: tegra: Fix FLOW_CTLR_HALT register clobbering by tegra_resume()
>   ARM: tegra: Use WFE for power-gating on Tegra30

Applied to for-5.5/arm/core, thanks.

Thierry

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