From: "Théo Lebrun" <theo.lebrun@bootlin.com>
To: "Mark Brown" <broonie@kernel.org>
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: Tue, 09 Apr 2024 12:09:17 +0200 [thread overview]
Message-ID: <D0FID4G7T4N0.194WATCMTOUEY@bootlin.com> (raw)
In-Reply-To: <9cb48440-c71e-4a73-8104-4780f0e98e72@sirena.org.uk>
Hello,
On Mon Apr 8, 2024 at 6:40 PM CEST, Mark Brown wrote:
> On Mon, Apr 08, 2024 at 04:42:43PM +0200, Théo Lebrun wrote:
> > On Mon Apr 8, 2024 at 4:16 PM CEST, Mark Brown wrote:
> > > On Fri, Apr 05, 2024 at 05:02:18PM +0200, Théo Lebrun wrote:
>
> > > > 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?
>
> > It does not make sense if you know that all read operations take more
> > than 100µs. I preferred being conservative. If you confirm it makes
> > sense I'll remove the quirk.
>
> It does seem plausible at least, and the time could be made a tuneable
> with quirks or otherwise if that's needed. I think I'd expect the MIPS
> platform you're working with to be towards the lower end of performance
> for systems that are new enough to have this hardware.
Next revision will do the same busywait behavior unconditionally then.
Thanks!
--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
next prev parent reply other threads:[~2024-04-09 10:09 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-05 15:02 [PATCH v2 00/11] spi: cadence-qspi: add Mobileye EyeQ5 support Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 01/11] spi: dt-bindings: cdns,qspi-nor: add mobileye,eyeq5-ospi compatible Théo Lebrun
2024-04-08 14:13 ` Mark Brown
2024-04-05 15:02 ` [PATCH v2 02/11] spi: dt-bindings: cdns,qspi-nor: sort compatibles alphabetically Théo Lebrun
2024-04-06 11:38 ` Krzysztof Kozlowski
2024-04-08 14:14 ` Mark Brown
2024-04-08 14:41 ` Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 03/11] spi: cadence-qspi: allow building for MIPS Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 04/11] spi: cadence-qspi: store device data pointer in private struct Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 05/11] spi: cadence-qspi: add FIFO depth detection quirk Théo Lebrun
2024-04-08 14:10 ` Mark Brown
2024-04-08 14:38 ` Théo Lebrun
2024-04-08 14:45 ` Théo Lebrun
2024-04-08 14:51 ` Mark Brown
2024-04-09 10:07 ` Théo Lebrun
2024-04-09 15:51 ` Mark Brown
2024-04-05 15:02 ` [PATCH v2 06/11] spi: cadence-qspi: minimise register accesses on each op if !DTR Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 07/11] spi: cadence-qspi: add no-IRQ mode to indirect reads Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 08/11] spi: cadence-qspi: add early busywait to cqspi_wait_for_bit() Théo Lebrun
2024-04-08 14:16 ` Mark Brown
2024-04-08 14:42 ` Théo Lebrun
2024-04-08 16:40 ` Mark Brown
2024-04-09 10:09 ` Théo Lebrun [this message]
2024-04-05 15:02 ` [PATCH v2 09/11] spi: cadence-qspi: add mobileye,eyeq5-ospi compatible Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 10/11] MIPS: mobileye: eyeq5: Add SPI-NOR controller node Théo Lebrun
2024-04-05 15:02 ` [PATCH v2 11/11] MIPS: mobileye: eyeq5: add octal flash node to eval board DTS Théo Lebrun
2024-04-05 15:30 ` [PATCH v2 00/11] spi: cadence-qspi: add Mobileye EyeQ5 support Théo Lebrun
2024-04-08 17:57 ` (subset) " Mark Brown
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