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From: <Tudor.Ambarus@microchip.com>
To: <yangyicong@hisilicon.com>, <linux-mtd@lists.infradead.org>
Cc: vigneshr@ti.com, sergei.shtylyov@cogentembedded.com,
	richard@nod.at, me@yadavpratyush.com, john.garry@huawei.com,
	linuxarm@huawei.com, alexander.sverdlin@nokia.com,
	miquel.raynal@bootlin.com, p.yadav@ti.com
Subject: Re: [PATCH 2/2] mtd: spi-nor: Disable the flash quad mode in spi_nor_restore()
Date: Thu, 2 Jul 2020 11:02:02 +0000	[thread overview]
Message-ID: <193b32f7-f56d-4f78-5353-b5d47cbf71d6@microchip.com> (raw)
In-Reply-To: <1592312547-19239-3-git-send-email-yangyicong@hisilicon.com>

On 6/16/20 4:02 PM, Yicong Yang wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> If the flash's quad mode is enabled, it'll remain in the quad mode when
> it's removed. If we drive the flash next time in SPI/Dual mode, then
> problem occurs as the flash's quad enable bit is not cleared.

Please describe the problems that occur. When QE bit is one the flash
operates in Standard/Dual/Quad SPI modes. WP# and RESET#/HOLD# are
affected as they change their functionality to IO2 and IO3 when QE
is 1. Is there anything else?

While I find the intention good, there might be some problems here:
1/ w25q jvm variants come with QE "fixed" to 1. This probably means
that QE is not writable, and a writing of QE to zero will be ignored,
but we have to check.
2/S25FS128S: CR1NV[1] can set the default power-on state for the
CR1V[1] to 1, i.e. QE to be set to 1 at power-on by default. The
logic here complicates a bit, and maybe we'll have to amend the
patch.

> 
> Disable the quad mode in spi_nor_restore(), the flash will leave
> quad mode when remove. This will make sure the flash always enter the
> correct mode when loaded.
s/correct/ Standard/Dual SPI

Cheers,
ta
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  reply	other threads:[~2020-07-02 11:05 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-16 13:02 [PATCH 0/2] Add support to Disable the flash quad mode Yicong Yang
2020-06-16 13:02 ` [PATCH 1/2] mtd: spi-nor: Add capability to disable " Yicong Yang
2020-07-02 11:07   ` Tudor.Ambarus
2020-06-16 13:02 ` [PATCH 2/2] mtd: spi-nor: Disable the flash quad mode in spi_nor_restore() Yicong Yang
2020-07-02 11:02   ` Tudor.Ambarus [this message]
2020-07-03 11:19     ` Pratyush Yadav
2020-07-03 11:52       ` Tudor.Ambarus
2020-07-06  6:47         ` Yicong Yang
2020-09-01  6:16   ` Matthias Weißer
2020-09-01  9:48     ` Pratyush Yadav
2020-09-01 10:08       ` Matthias Weißer
2020-09-01 11:11         ` Pratyush Yadav
2020-09-01 11:41     ` Yicong Yang
2020-09-01 14:20     ` Yicong Yang
2020-09-02  7:50       ` Vignesh Raghavendra
2020-09-02 10:12         ` Yicong Yang
2020-09-03  5:59           ` Vignesh Raghavendra
2020-09-04  7:54             ` Yicong Yang
2020-09-04  9:35               ` Matthias Weißer
2020-09-02 12:15       ` Matthias Weißer
2020-09-03  3:03         ` Yicong Yang
2020-09-03  5:33           ` Matthias Weißer
2020-09-04  7:56             ` Yicong Yang

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