linux-kernel - Re: [PATCH v3 1/4] ARM: dts: at91-sama5d27_wlsom1: Set sst26vf064b SPI NOR flash at its maximum frequency

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Message-ID: <026b9d7d-86db-45cd-9e86-066fa826a77e@linaro.org>
Date:   Tue, 28 Mar 2023 11:23:18 +0100
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com
Cc:     alexandre.belloni@...tlin.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tudor Ambarus <tudor.ambarus@...rochip.com>
Subject: Re: [PATCH v3 1/4] ARM: dts: at91-sama5d27_wlsom1: Set sst26vf064b
 SPI NOR flash at its maximum frequency



On 3/28/23 11:15, Tudor Ambarus wrote:
> From: Tudor Ambarus <tudor.ambarus@...rochip.com>
> 

cut

> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>

I don't understand why these differ. On my local machine I see them match:

commit e208a7b04cbde950588c561889d2f8eb8a10485f
Author: Tudor Ambarus <tudor.ambarus@...aro.org>
Date:   Thu Nov 17 12:52:46 2022 +0200

    ARM: dts: at91-sama5d27_wlsom1: Set sst26vf064b SPI NOR flash at its
maximum frequency

    sama5d27-wlsom1 populates an sst26vf064b SPI NOR flash. Its maximum
    operating frequency for 2.7-3.6V is 104 MHz. As the flash is operated
    at 3.3V, increase its maximum supported frequency to 104MHz. The
    increasing of the spi-max-frequency value requires the setting of the
    "CE# Not Active Hold Time", thus set the spi-cs-setup-ns to a value
of 7.

    The sst26vf064b datasheet specifies just a minimum value for the
    "CE# Not Active Hold Time" and it advertises it to 5 ns. There's no
    maximum time specified. I determined experimentally that 5 ns for the
    spi-cs-setup-ns is not enough when the flash is operated close to its
    maximum frequency and tests showed that 7 ns is just fine, so set the
    spi-cs-setup-ns dt property to 7.

    With the increase of frequency the reads are now faster with ~37%.

    Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>

Anyway, you can keep v2 then, looks like v2 has the same email on both
the author line and the S-o-b line. It's fine by me even if it is with
@microchip.com:
https://lore.kernel.org/all/20230328100723.1593864-2-tudor.ambarus@linaro.org/