From: <Tudor.Ambarus@microchip.com>
To: <dac2@pensando.io>
Cc: snelson@pensando.io, linux-mtd@lists.infradead.org, vigneshr@ti.com
Subject: Re: [PATCH 2/2] mtd: spi-nor: Support SPI_NOR_DUAL_READ on Micron mt25qu02g.
Date: Sat, 18 Jul 2020 05:35:06 +0000 [thread overview]
Message-ID: <6c29b0f3-65d3-1e69-58ce-cbb84c88910a@microchip.com> (raw)
In-Reply-To: <CA+nMikFFaxZxNP_d24+YGWfWG1yAV41FRyxQn=gweY0-T3aV_A@mail.gmail.com>
Hi, David,
On 7/17/20 9:00 PM, David Clear wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> On Fri, Jul 17, 2020 at 3:33 AM <Tudor.Ambarus@microchip.com> wrote:
>> On 7/17/20 12:16 AM, David Clear wrote:
>>> The Micron mt25qu02g supports both x2 and x4 transactions. Add the
>>> SPI_NOR_DUAL_READ to its spi_nor_ids[] table entry.
>>
>> In spi_nor_select_read() we select the fastest read. Since this flash
>> supports Quad Read, the Dual Read will never get selected. As of now,
>> there is no benefit in adding SPI_NOR_DUAL_READ when SPI_NOR_QUAD_READ
>> is specified.
>
> Ok, I've got this now: I went back and did some more testing with different
> spi-rx-bus-width properties and I see it's redundant to specify both DUAL and
> QUAD in the flash description. Thanks for pointing out my error. I learned
> something new.
>
> I withdraw this patch and will work on getting the Macronix patch cleaned up and
> tests documented.
No, please keep this patch as well. You were right. If we remove the
SPI_NOR_DUAL_READ flag, the dual read will work only because the SPI_NOR_QUAD_READ
flag triggers the parsing of SFDP, which will fill the dual read caps. It is
better to statically fill the 1-1-2 read, so that we can still use the dual read
if SFDP parsing fails and will not fill the dual read caps. Let's keep it.
Thanks, David.
ta
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next prev parent reply other threads:[~2020-07-18 5:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-16 21:16 [PATCH 0/2] Support flash devices used on Pensando boards David Clear
2020-07-16 21:16 ` [PATCH 1/2] mtd: spi-nor: Add support for Macronix mx66u2g45g David Clear
2020-07-17 10:38 ` Tudor.Ambarus
[not found] ` <CA+nMikGEEOoKri5z2T3Ms-3cEi+G014ha+rwrwZWeRn=DxfU9w@mail.gmail.com>
2020-07-17 16:44 ` Fwd: " David Clear
2020-07-16 21:16 ` [PATCH 2/2] mtd: spi-nor: Support SPI_NOR_DUAL_READ on Micron mt25qu02g David Clear
2020-07-17 10:33 ` Tudor.Ambarus
[not found] ` <CA+nMikFDWgLMAhb2rUZnAaLUJdimKZZxqKsQACnXrmCMb_CLMw@mail.gmail.com>
2020-07-17 16:42 ` Fwd: " David Clear
2020-07-17 18:00 ` David Clear
2020-07-18 5:35 ` Tudor.Ambarus [this message]
2020-07-18 17:23 ` David Clear
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