Re: Aspeed SPI driver upstreaming

From: "Cédric Le Goater" <clg@kaod.org>
To: Patrick Williams <patrick@stwcx.xyz>
Cc: openbmc@lists.ozlabs.org, taoren@fb.com, joel@jms.id.au
Subject: Re: Aspeed SPI driver upstreaming
Date: Mon, 13 Jan 2020 09:02:55 +0100	[thread overview]
Message-ID: <b851479c-865e-74a2-bdae-23f065dd1867@kaod.org> (raw)
In-Reply-To: <20200109164317.GE1233@patrickw3-mbp.dhcp.thefacebook.com>

On 1/9/20 5:43 PM, Patrick Williams wrote:
> Thanks for the reply Cédric.
> 
> On Tue, Jan 07, 2020 at 09:34:03AM +0100, Cédric Le Goater wrote:
>> Regarding the SMC driver, the maintainers are requesting a rewrite 
>> of the driver using the spimem layer, but we lack handlers to do 
>> the read training and compute the timing register value.
>>
>> This is the first thing to address on the todo list. When available,
>> it shouldn't take too long to upstream the driver. Some more info 
>> here :
>>
>>    https://www.spinics.net/lists/linux-mtd/msg09417.html
>>
> 
> It looks like this patch set is still the MTD-only implementation, which
> is useful for SPI-NOR chips but not useful for non-flash devices such as
> TPMs.  Is there any work or thought into how we could do a generic SPI
> controller and then layer the MTD above it?

Not on my side. I always worked with flash support in mind.

> We have some system designs where we have both a NOR device and a TPM on
> the same SPI bus.  What we're currently doing is using the
> (non-upstream) aspeed-spi driver which lets us use both the TPM and
> MTD/SPI-NOR driver, but since it doesn't have the calibration routines
> the SPI-NOR runs at a slower speed than optimal.
> 
> I'd really like to get a generic SPI controller driver upstreamed, even if it
> doesn't have the calibration (the SPI-NOR device in this case is not as
> performance critical as the BMC's own NOR devices).  Is there any path
> to combining the features of the aspeed-smc and aspeed-spi into a single
> driver, or do you think we should start with them as separate and get
> aspeed-spi upstreamed as an alternative to aspeed-smc?

Yes, we should and this is requested by the MTD community which wants
to deprecate SPI-NOR.

> Also, do you have any soft timeline on the follow-ups to this patch set?

AST2600 was done on my spare time this year. I have been working on the 
other side of the system (PowerPC XIVE) these last two/three years and 
should continue to do so.

If a new Aspeed flash driver should emerge, I think some else should take 
ownership. It will be better for maintenance

Cheers,

C.