Re: [PATCH RFC 0/4] Add set_iofv() callback

From: Michael Walle <michael@walle.cc>
To: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Mark Brown <broonie@kernel.org>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	linux-spi@vger.kernel.org, linux-mtd@lists.infradead.org,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	"biju.das.au" <biju.das.au@gmail.com>,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH RFC 0/4] Add set_iofv() callback
Date: Fri, 10 Nov 2023 11:11:00 +0100	[thread overview]
Message-ID: <dcfa2cab21fc85bb9b2b0c1ceb754a1a@walle.cc> (raw)
In-Reply-To: <TYCPR01MB112699263B2EC0EC229746D3786AFA@TYCPR01MB11269.jpnprd01.prod.outlook.com>

Hi Biju,

>> >> Thus I was saying, that we probably wont support that and the easiest
>> >> fix should be to disable this behavior for the atmel flash (there was
>> >> nv setting).
>> >
>> > The fix up is invoked only for quad mode, I believe it is safe to add
>> > fixup for micron flash As it is the one deviating from normal
>> > according to you, rather than adding fixup for generic flash like
>> > ATMEL flash(Now Renesas flash)
>> 
>> Could you please try setting bit 4 in the Nonvolatile Configuration
>> Register (Table 7) and see if the problem goes away?
> 
> You mean, if it works, we need to disable reset for all the boards, 
> maybe at bootloader level??

Not necessarily. First, just to confirm that it is actually the reset
circuit. You can also compare the part numbers of the flash. There
is a flash with IO3/RESET# and IO3/HOLD# (and a flash with a dedicated
reset pin).

If that's the case, it looks like a hardware bug on your board. You
left the reset pin floating. So you'd also not be able to boot from
the NOR flash, right?

> OK, I will check that. Currently I have read that register and it is 
> showing a value
> Of 0xffbb. I need to do write operation. Before that how do we recover 
> flash, if
> something goes wrong during writing for NV register?

You should always be able to write that register from the bootloader.
Maybe also through raw commands (like sspi in uboot).

>> Also could you have a look at the schematics, does the IO3/RESET# have 
>> a
>> pull-up? If not, who is in control of driving the correct value here? 
>> If
>> it has a pull-up, I'm puzzled why you need any other setting than HiZ.
> 
> Unfortunately, there is no pullup on IO3 line and also there is no SoC 
> pullup.

See above.

-michael

>> The correct fix would be to the information about the missing IO state 
>> in
>> the "struct spi_mem_op". That is, what should be the default values of 
>> all
>> the IO lines which are unused. For example if we have a 1s1s4s
>> transaction, what should be the state of IO0,
>> IO2 and IO3 during the command and address phase. If we have a 1s2s2s,
>> what should be the state of IO0 during the command phase etc.
>> 
>> That can then be used within your driver to set the corresponding IOFV
>> values (for each spi-mem op).
>> 
>> But I'm not sure if other SPI controllers will support that, though.
> 
> Currently driving SoC IOFV register, it fixes the issue and it is just 
> one time
> operation during post sfdp. I take this as a SoC feature which other 
> controllers
> don't have.
> 
> Cheers,
> Biju

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