linux-kernel - Re: [PATCH v2 0/9] mtd: spi-nor: parse SFDP tables to setup (Q)SPI memories

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Date:   Sat, 22 Oct 2016 22:33:29 +0200
From:   Marek Vasut <marex@...x.de>
To:     Jagan Teki <jagan@...nedev.com>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Cc:     Brian Norris <computersforpeace@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        nicolas.ferre@...el.com, boris.brezillon@...e-electrons.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/9] mtd: spi-nor: parse SFDP tables to setup (Q)SPI
 memories

On 10/22/2016 01:00 PM, Jagan Teki wrote:
> On Wed, Oct 5, 2016 at 5:30 PM, Cyrille Pitchen
> <cyrille.pitchen@...el.com> wrote:
>> Hi all,
>>
>> This series extends support of SPI protocols to new protocols such as
>> SPI x-2-2 and SPI x-4-4. Also spi_nor_scan() tries now to select the right
>> op codes, timing parameters (number of mode and dummy cycles) and erase
>> sector size by parsing the Serial Flash Discoverable Parameter (SFDP)
>> tables, when available, as defined in the JEDEC JESD216 specifications.
>>
>> When SFDP tables are not available, legacy settings are still used for
>> backward compatibility (SPI and earlier QSPI memories).
>>
>> Support of SPI memories >128Mbits is also improved by using the 4byte
>> address instruction set, when available. Using those dedicated op codes
>> is stateless as opposed to enter the 4byte address mode, hence a better
>> compatibility with some boot loaders which expect to use 3byte address
>> op codes.
> 
> The memories which are > 128Mbits should have 4-bytes addressing
> support based on my experience, do you think BAR is also required
> atleast from spi-nor side?

Yes, I believe BAR is still required for broken/dumb flash chips.
Not all chips > 16 MiB support dedicated 4-byte addressing opcodes :-(

-- 
Best regards,
Marek Vasut