From: Jon Hunter <jonathanh@nvidia.com>
To: Abraham Zukor <abe@maticrobots.com>,
Mark Brown <broonie@kernel.org>,
Laxman Dewangan <ldewangan@nvidia.com>
Cc: Thierry Reding <thierry.reding@kernel.org>,
linux-spi@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] spi: tegra114: initialize native chip selects inactive
Date: Tue, 28 Jul 2026 10:34:52 +0100 [thread overview]
Message-ID: <9c196ab1-1945-49fc-a89a-5588d1e50046@nvidia.com> (raw)
In-Reply-To: <20260728025503.162543-1-abe@maticrobots.com>
On 28/07/2026 03:53, Abraham Zukor wrote:
> On 27/07/2026 13:07, Jon Hunter wrote:
>> What about the case where the SPI devices CS is active high or a
>> mixture of the two?
>
> An all-active-high bus is the case the window gets right today: probe
> writes zero to the field, so an active-high CS idles deasserted and an
> active-low one sits asserted. This patch inverts that. No single
> constant covers a mixed board - one polarity or the other is asserted
> until tegra_spi_setup() runs for that device - so the question is
> which default is the right one, and active low is what the SPI core
> assumes when a device says nothing.
Exactly. That's my point. Which is the right one? The answer is probably
neither, but whatever is present on the bus.
--
nvpublic
next prev parent reply other threads:[~2026-07-28 9:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-25 4:29 [PATCH] spi: tegra114: initialize native chip selects inactive Abraham Zukor
2026-07-27 12:07 ` Jon Hunter
2026-07-28 2:53 ` Abraham Zukor
2026-07-28 9:34 ` Jon Hunter [this message]
2026-07-28 20:03 ` Abraham Zukor
2026-07-28 21:09 ` Jon Hunter
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