Re: [PATCH 2/3] mtd: spi-nor: add support for Quad Page Program to no_sfdp_flags

From: <Tudor.Ambarus@microchip.com>
To: <sudip.mukherjee@sifive.com>
Cc: <p.yadav@ti.com>, <michael@walle.cc>, <miquel.raynal@bootlin.com>,
	<richard@nod.at>, <vigneshr@ti.com>, <greentime.hu@sifive.com>,
	<jude.onyenegecha@sifive.com>, <william.salmon@sifive.com>,
	<adnan.chowdhury@sifive.com>, <ben.dooks@sifive.com>,
	<linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] mtd: spi-nor: add support for Quad Page Program to no_sfdp_flags
Date: Fri, 29 Jul 2022 07:48:13 +0000	[thread overview]
Message-ID: <d5662307-200e-171d-58fd-8f26dc02c771@microchip.com> (raw)
In-Reply-To: <CAHyZL-c9iSd8=CaQ00Nptea4cqp9f7oqS5VefT3vfcr2J3hmSQ@mail.gmail.com>

On 7/22/22 13:24, Sudip Mukherjee wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Hi Tudor,
> 

Hi!

> On Mon, Jul 18, 2022 at 7:49 PM Sudip Mukherjee
> <sudip.mukherjee@sifive.com> wrote:
>>
>> On Mon, Jul 18, 2022 at 6:02 PM <Tudor.Ambarus@microchip.com> wrote:
>>>
>>> On 7/12/22 19:38, Sudip Mukherjee wrote:
>>>> [You don't often get email from sudip.mukherjee@sifive.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>>>>
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> Some flash chips which does not have a SFDP table can support Quad
>>>> Input Page Program. Enable it in hwcaps if defined.
>>>>
>>
>> <snip>
>>
>>>> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
>>>> index 58fbedc94080f..dde636bdb1a7c 100644
>>>> --- a/drivers/mtd/spi-nor/core.h
>>>> +++ b/drivers/mtd/spi-nor/core.h
>>>> @@ -462,6 +462,7 @@ struct spi_nor_fixups {
>>>>   *   SPI_NOR_OCTAL_READ:      flash supports Octal Read.
>>>>   *   SPI_NOR_OCTAL_DTR_READ:  flash supports octal DTR Read.
>>>>   *   SPI_NOR_OCTAL_DTR_PP:    flash supports Octal DTR Page Program.
>>>> + *   SPI_NOR_QUAD_PP:         flash supports Quad Input Page Program.
>>>
>>> You don't need this flag if your flash supports the 4-byte Address
>>> Instruction Table. Does you flash support it? Can you dump all the
>>> SFDP tables, please?
>>
>> Not sure what the correct way to dump sfdp is. I did this from sysfs.
> 
> I tried decoding this SFDP table and I think the parameters table says
> it has "3-Byte only addressing".
> So, I guess that means it does not support 4-byte Address Instruction
> Table. And the datasheet
> says it supports "Quad Input Page Program (3-byte Address)".
> My existing patchset works for Quad Input Page Program, and I can send
> a v2 with the previous
> patch and this merged together (as you suggested) or I can try
> enabling sfdp for this chip and then use

You should definitely enable SFDP and get rid of the NO_SFDP_FLAGS flags,
regardless of the 1-1-4 PP outcome.

> a fixup_flags to enable "Quad Input Page Program" which I think will
> be more complicated.
> Which one will you suggest?
> 

First I'd like to understand what "much better performance" means. Would
you run some speed tests please? mtd-utils should have a speedtest, otherwise
you can use the in kernel mtd_speedtest module. Page programs are slow anyway,
using 4 lines may not make any difference. But let's see.

About your question, it depends on how common is 1-1-4 pp. If it's common and
desirable we can introduce a flash info flag.

-- 
Cheers,
ta
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