From: Mark Brown <broonie@kernel.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Niklas Cassel <niklas.cassel@linaro.org>,
Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>,
Andy Gross <andy.gross@linaro.org>,
David Brown <david.brown@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
Khasim Syed Mohammed <khasim.mohammed@linaro.org>
Subject: Re: [PATCH] arm64: dts: qcs404: evb: Fix voltages for s5 and l3
Date: Mon, 4 Feb 2019 21:59:30 +0100 [thread overview]
Message-ID: <20190204205930.GK23441@sirena.org.uk> (raw)
In-Reply-To: <20190204192510.GZ31919@minitux>
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On Mon, Feb 04, 2019 at 11:25:10AM -0800, Bjorn Andersson wrote:
> On Mon 04 Feb 10:23 PST 2019, Mark Brown wrote:
> > On Mon, Feb 04, 2019 at 08:03:37AM -0800, Bjorn Andersson wrote:
> Okay, I don't see a big problem with expecting the DT to only contain
> values that the hardware can actually do. I do however see that
> machine_constraints_voltage() has been changes to expect the driver to
> return -ENOTRECOVERABLE when we don't have a way to query the voltage
> during probe.
> So there's a risk of this breaking compatibility with older dtb files on
> other boards. We will have to do some more verification on this.
That's basically only going to affect Qualcomm hardware FWIW, I had
thought that such devices didn't manage to probe with upstream before
that change either but I could be misremembering.
> > > regulator framework be made to round down to the previous valid step
> > > instead of up?
> > We definitely don't want to round voltages down, it is vastly more
> > common for devices to experience problems like brownouts if they go
> > under voltage so it'd be more likely to cause harm than good.
> We're 2mV off in this case, but it could have been way off. So I'm good
> with this position.
Never mind that that's 2mV assuming the regulator has perfect accuracy
and there's headroom. For something like this it's likely not a problem
but some high current things (especially CPUs or anything like that) are
operating on thin margins.
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prev parent reply other threads:[~2019-02-04 20:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-25 23:29 Bjorn Andersson
2019-01-29 21:58 ` Jorge Ramirez
2019-01-29 22:46 ` Niklas Cassel
2019-02-04 10:43 ` Mark Brown
2019-02-04 16:03 ` Bjorn Andersson
2019-02-04 18:23 ` Mark Brown
2019-02-04 19:25 ` Bjorn Andersson
2019-02-04 20:59 ` Mark Brown [this message]
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