Re: [PATCH v2 08/11] spi: cadence-qspi: add early busywait to cqspi_wait_for_bit()

From: Mark Brown <broonie@kernel.org>
To: "Théo Lebrun" <theo.lebrun@bootlin.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Vaishnav Achath <vaishnav.a@ti.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Rob Herring <robh@kernel.org>,
	linux-spi@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
	Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>,
	Gregory CLEMENT <gregory.clement@bootlin.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Tawfik Bayouk <tawfik.bayouk@mobileye.com>
Subject: Re: [PATCH v2 08/11] spi: cadence-qspi: add early busywait to cqspi_wait_for_bit()
Date: Mon, 8 Apr 2024 15:16:29 +0100	[thread overview]
Message-ID: <1f7087ad-824e-47fe-9953-ed5152c8f18f@sirena.org.uk> (raw)
In-Reply-To: <20240405-cdns-qspi-mbly-v2-8-956679866d6d@bootlin.com>

[-- Attachment #1: Type: text/plain, Size: 612 bytes --]

On Fri, Apr 05, 2024 at 05:02:18PM +0200, Théo Lebrun wrote:

> If the CQSPI_BUSYWAIT_EARLY quirk flag is on, call
> readl_relaxed_poll_timeout() with no sleep at the start of
> cqspi_wait_for_bit(). If its short timeout expires, a sleeping
> readl_relaxed_poll_timeout() call takes the relay.
> 
> Behavior is hidden behind a quirk flag to keep the previous behavior the
> same on all platforms.
> 
> The reason is to avoid hrtimer interrupts on the system. All read
> operations take less than 100µs.

Why would this be platform specific, this seems like a very standard
optimisation technique?

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]