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

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Date:   Mon, 24 Oct 2016 13:11:29 +0530
From:   Jagan Teki <jagan@...nedev.com>
To:     Marek Vasut <marex@...x.de>
Cc:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        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 Sun, Oct 23, 2016 at 2:03 AM, Marek Vasut <marex@...x.de> wrote:
> 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 :-(

Do you have list for those broken chips? because I never find any
chips which has > 16 MiB with not support of 4-byte address opcodes
and I've seen the controller has dependable with BAR though it can
access > 16MiB ex: zynq qspi/

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.