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To:     "Pratyush Yadav" <me@yadavpratyush.com>
Cc:     boris.brezillon@collabora.com, broonie@kernel.org,
        juliensu@mxic.com.tw, linux-kernel@vger.kernel.org,
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        richard@nod.at, tudor.ambarus@microchip.com, vigneshr@ti.com
Subject: Re: [PATCH v4 1/7] mtd: spi-nor: sfdp: get octal mode maximum speed from
 BFPT
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Message-ID: <OF61F39C24.01B2337A-ON4825857B.00238327-4825857B.0023F82E@mxic.com.tw>
From:   masonccyang@mxic.com.tw
Date:   Tue, 2 Jun 2020 14:32:53 +0800
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Hi Pratyush,

> 
> Subject
> 
> Re: [PATCH v4 1/7] mtd: spi-nor: sfdp: get octal mode maximum speed from 
BFPT
> 
> On 29/05/20 03:36PM, Mason Yang wrote:
> > Get maximum operation speed of device in octal mode from
> > BFPT 20th DWORD.
> 
> I don't like the idea of getting the maximum operation speed from BFPT 
> when the Profile 1.0 table already tells us that. For example, the 
> 200MHz operation dummy cycles field in the 4th DWORD says that a value 
> of 0 means the frequency is not supported. So the Profile 1.0 table 
> already tells us what frequencies the flash can run at in xSPI Profile 
> 1.0 mode.

As JEDEC spec. mentioned that 
Operation faster than 200MHz is not part of the current xSPI Spec. 
However, this does not prevent vendors from making devices that operate at 
higher speed.

In addition, current xSPP profile 1.0 table only defined up to 200MHz.

> 
> So IMO we should use the Profile 1.0 table for this instead because
> it will be a localized change which is easier to maintain. I also get 
> the feeling it will be less prone to mis-interpretations.
> 
> > Signed-off-by: Mason Yang <masonccyang@mxic.com.tw>
> > ---

thanks for your time & comments.
Mason

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