From: Matthias Kaehlcke <mka@chromium.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
Stephen Boyd <swboyd@chromium.org>,
Andy Gross <agross@kernel.org>, Rob Herring <robh+dt@kernel.org>,
devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sc7280-herobrine: Fix PCIe regulator glitch at bootup
Date: Thu, 10 Mar 2022 14:34:56 -0800 [thread overview]
Message-ID: <Yip9EE+gcyRcSydd@google.com> (raw)
In-Reply-To: <20220310130429.1.Id41fda1d7f5d9230bc45c1b85b06b0fb0ddd29af@changeid>
On Thu, Mar 10, 2022 at 01:04:34PM -0800, Douglas Anderson wrote:
> While scoping signals, we found that the PCIe signals weren't
> compliant at bootup. Specifically, the bootloader was setting up PCIe
> and leaving it configured, then jumping to the kernel. The kernel was
> turning off the regulator while leaving the PCIe clock running, which
> was a violation.
>
> In the regulator bindings (and the Linux kernel driver that uses
> them), there's currently no way to specify that a GPIO-controlled
> regulator should keep its state at bootup. You've got to pick either
> "on" or "off". Let's switch it so that the PCIe regulator defaults to
> "on" instead of "off". This should be a much safer way to go and
> avoids the timing violation. The regulator will still be turned off
> later if there are no users.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
next prev parent reply other threads:[~2022-03-10 22:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 21:04 [PATCH] arm64: dts: qcom: sc7280-herobrine: Fix PCIe regulator glitch at bootup Douglas Anderson
2022-03-10 22:34 ` Matthias Kaehlcke [this message]
2022-03-10 22:49 ` Stephen Boyd
2022-04-11 21:00 ` patchwork-bot+linux-arm-msm
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