From: Peter Geis <pgwipeout@gmail.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Peter De Schrijver <pdeschrijver@nvidia.com>,
linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] ARM: tegra: Use WFE for power-gating on Tegra30
Date: Sat, 5 Oct 2019 11:12:07 -0400 [thread overview]
Message-ID: <CAMdYzYq8YvzOnLnTbt5-=cBC8BGXN1pZnpPmcHyitGRs467zfg@mail.gmail.com> (raw)
In-Reply-To: <20190730172340.14037-3-digetx@gmail.com>
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
>
next prev parent reply other threads:[~2019-10-05 15:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 17:23 [PATCH v2 0/2] Tegra30+ CPU suspend-resume bug-fixes Dmitry Osipenko
2019-07-30 17:23 ` [PATCH v2 1/2] ARM: tegra: Fix FLOW_CTLR_HALT register clobbering by tegra_resume() Dmitry Osipenko
2019-07-30 17:23 ` [PATCH v2 2/2] ARM: tegra: Use WFE for power-gating on Tegra30 Dmitry Osipenko
2019-10-05 15:12 ` Peter Geis [this message]
2019-10-29 13:33 ` [PATCH v2 0/2] Tegra30+ CPU suspend-resume bug-fixes Thierry Reding
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