From: Pratyush Yadav <p.yadav@ti.com>
To: "Cédric Le Goater" <clg@kaod.org>
Cc: <linux-spi@vger.kernel.org>, <linux-mtd@lists.infradead.org>,
Mark Brown <broonie@kernel.org>,
Tudor Ambarus <tudor.ambarus@microchip.com>,
Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
<linux-aspeed@lists.ozlabs.org>, Joel Stanley <joel@jms.id.au>,
Andrew Jeffery <andrew@aj.id.au>,
Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>,
<devicetree@vger.kernel.org>, Rob Herring <robh+dt@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 08/10] spi: aspeed: Calibrate read timings
Date: Fri, 25 Feb 2022 14:48:09 +0530 [thread overview]
Message-ID: <20220225091809.gvup3mcst45szi6x@ti.com> (raw)
In-Reply-To: <20220214094231.3753686-9-clg@kaod.org>
On 14/02/22 10:42AM, Cédric Le Goater wrote:
> To accommodate the different response time of SPI transfers on different
> boards and different SPI NOR devices, the Aspeed controllers provide a
> set of Read Timing Compensation registers to tune the timing delays
> depending on the frequency being used. The AST2600 SoC has one of
> these registers per device. On the AST2500 and AST2400 SoCs, the
> timing register is shared by all devices which is a bit problematic to
> get good results other than for one device.
>
> The algorithm first reads a golden buffer at low speed and then performs
> reads with different clocks and delay cycle settings to find a breaking
> point. This selects a default good frequency for the CEx control register.
> The current settings are bit optimistic as we pick the first delay giving
> good results. A safer approach would be to determine an interval and
> choose the middle value.
>
> Due to the lack of API, calibration is performed when the direct mapping
> for reads is created.
The dirmap_create mapping says nothing about _when_ it should be called.
So there is no guarantee that it will only be called after the flash is
fully initialized. I suggest you either make this a requirement of the
API, or create a new API that guarantees it will only be called after
the flash is initialized, like [0].
[0] https://patchwork.ozlabs.org/project/linux-mtd/patch/20210311191216.7363-2-p.yadav@ti.com/
>
> Cc: Pratyush Yadav <p.yadav@ti.com>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
--
Regards,
Pratyush Yadav
Texas Instruments Inc.
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next prev parent reply other threads:[~2022-02-25 9:19 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 9:42 [PATCH 00/10] spi: spi-mem: Add driver for Aspeed SMC controllers Cédric Le Goater
2022-02-14 9:42 ` [PATCH 01/10] mtd: spi-nor: aspeed: Rename Kconfig option Cédric Le Goater
2022-02-25 7:31 ` Pratyush Yadav
2022-02-27 18:50 ` Cédric Le Goater
2022-02-28 6:07 ` Joel Stanley
2022-02-28 14:37 ` Cédric Le Goater
2022-02-14 9:42 ` [PATCH 02/10] dt-bindings: spi: Add Aspeed SMC controllers device tree binding Cédric Le Goater
2022-02-15 19:49 ` Rob Herring
2022-02-15 21:06 ` Rob Herring
2022-02-17 8:37 ` Cédric Le Goater
2022-02-14 9:42 ` [PATCH 03/10] spi: spi-mem: Add driver for Aspeed SMC controllers Cédric Le Goater
[not found] ` <20220215062743.GA12431@wunner.de>
2022-02-15 9:07 ` Cédric Le Goater
2022-02-25 7:50 ` Pratyush Yadav
2022-02-27 18:46 ` Cédric Le Goater
2022-02-14 9:42 ` [PATCH 04/10] spi: aspeed: Add support for direct mapping Cédric Le Goater
2022-02-25 9:12 ` Pratyush Yadav
2022-02-27 21:06 ` Cédric Le Goater
2022-02-14 9:42 ` [PATCH 05/10] spi: aspeed: Adjust direct mapping to device size Cédric Le Goater
2022-02-14 9:42 ` [PATCH 06/10] spi: aspeed: Workaround AST2500 limitations Cédric Le Goater
2022-02-14 9:42 ` [PATCH 07/10] spi: aspeed: Add support for the AST2400 SPI controller Cédric Le Goater
2022-02-14 9:42 ` [PATCH 08/10] spi: aspeed: Calibrate read timings Cédric Le Goater
2022-02-25 9:18 ` Pratyush Yadav [this message]
2022-02-27 21:27 ` Cédric Le Goater
2022-02-14 9:42 ` [PATCH 09/10] ARM: dts: aspeed: Enable Dual SPI RX transfers Cédric Le Goater
2022-02-16 7:21 ` Joel Stanley
2022-02-14 9:42 ` [PATCH 10/10] spi: aspeed: Activate new spi-mem driver Cédric Le Goater
2022-02-16 7:02 ` Joel Stanley
2022-02-16 8:12 ` Cédric Le Goater
2022-02-16 7:21 ` [PATCH 00/10] spi: spi-mem: Add driver for Aspeed SMC controllers Joel Stanley
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