From: Abraham Zukor <abe@maticrobots.com>
To: Mark Brown <broonie@kernel.org>
Cc: Abraham Zukor <abe@maticrobots.com>,
Jon Hunter <jonathanh@nvidia.com>,
Laxman Dewangan <ldewangan@nvidia.com>,
Mikko Perttunen <mperttunen@nvidia.com>,
Thierry Reding <thierry.reding@kernel.org>,
linux-spi@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] spi: tegra114: initialize native chip selects inactive
Date: Tue, 15 Sep 2026 19:00:28 -0700 [thread overview]
Message-ID: <20260916020031.161347-1-abe@maticrobots.com> (raw)
In-Reply-To: <c6868d2a-f55f-4196-9914-f096420cbabc@sirena.org.uk>
On Thu, Aug 27, 2026 at 04:38:39PM +0100, Mark Brown wrote:
> I can see a system having multiple variants with the bootloader
> selecting which device is active in the DT based on runtime
> enumeration. Not sure if anyone is *actually* doing that, but given
> the state of the world with overlays...
I think we should handle this per native chip select:
If exactly one node is enabled, use its polarity, ignoring disabled
alternatives.
If none are enabled, use the polarity specified by the disabled nodes
when they agree, including when there is only one. If they disagree, log
a warning and use the polarity of one of them, since no inactive level
can satisfy both polarities.
Multiple enabled nodes using the same CS are a configuration error that
the SPI core already checks.
My v3 needs adjusting for the first case. I will implement this as a v4
if no one sees an issue.
prev parent reply other threads:[~2026-09-16 2:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-26 0:05 Abraham Zukor
2026-08-27 15:18 ` Jon Hunter
2026-08-27 15:38 ` Mark Brown
2026-09-16 2:00 ` Abraham Zukor [this message]
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