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From: Boris Brezillon <boris.brezillon@collabora.com>
To: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: Dirk Behme <dirk.behme@de.bosch.com>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Richard Weinberger <richard@nod.at>,
	Mark Brown <broonie@kernel.org>,
	linux-mtd@lists.infradead.org,
	Miquel Raynal <miquel.raynal@bootlin.com>
Subject: Re: [PATCH RFT 0/2/2] mtd: hyperbus: add Renesas RPC-IF driver
Date: Thu, 20 Feb 2020 08:49:27 +0100	[thread overview]
Message-ID: <20200220084927.7a411d40@collabora.com> (raw)
In-Reply-To: <20200220084623.3d5145fd@collabora.com>

On Thu, 20 Feb 2020 08:46:23 +0100
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> On Wed, 19 Feb 2020 23:13:36 +0300
> Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> wrote:
> 
> > > One way would be to extend spi_mem_op to support above template along
> > > with a new field to distinguish SPI NOR vs HyperFlash protocol. HyperBus
> > > core can then register a spi_device and use spi-mem ops to talk to
> > > controller driver.    
> > 
> >    We have discussed this idea with Mark Brown, the SPI maintainer, and
> > he wasn't terribly impressed (I've invited him to #mtd -- his nick is
> > broonie and mine is headless, I'm also adding him to CC:).
> >   
> > > So, I suggest making Renesas RPC-IF backend a full fledged spi-mem
> > > driver (instead of driver/memory) and use extended spi_mem_op to support
> > > HyperFlash.    
> > 
> >    I don't think cramming support for the different flash busses into
> > the SPI drivers is a good idea...  
> 
> That's what I thought at first (SPI and Hyperflash seemed different
> enough to not merge them), then I had a look at Vignesh's HyperFlash
> presentation [1], and there's one aspect that made me reconsider this
> PoV. Slide 25 (xSPI compliant HyperFlash): having devices bouncing from
> one driver to another depending on the mode they operate in is likely to
> be painful to handle. Not to mention that Octo+DTR is similar to
> HyperBus from an HW PoV (at the PHY level, they both have CS, CLK,
> DQS/RWDS, DQ/IO[0:7] signals, only the protocol differs).

This doc [2] also shows the similarities between HyperBus and
Octal+DTR-SPI.

> 
> [1]https://elinux.org/images/3/38/HBMC-v1.pdf

[2]https://www.st.com/content/ccc/resource/technical/document/application_note/group0/91/dd/af/52/e1/d3/48/8e/DM00407776/files/DM00407776.pdf/jcr:content/translations/en.DM00407776.pdf


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      reply	other threads:[~2020-02-20  7:49 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29 20:32 [PATCH RFT 0/2] Add RPC-IF HyperFlash driver Sergei Shtylyov
2020-01-29 20:37 ` [PATCH RFT 1/2] mtd: hyperbus: move direct mapping setup to AM654 HBMC driver Sergei Shtylyov
2020-03-13  5:21   ` Vignesh Raghavendra
2020-01-29 20:39 ` [PATCH RFT 0/2/2] mtd: hyperbus: add Renesas RPC-IF driver Sergei Shtylyov
2020-02-03  4:59   ` Vignesh Raghavendra
2020-02-03 11:46     ` Sergei Shtylyov
2020-02-07 12:59   ` Behme Dirk (CM/ESO2)
2020-02-07 19:09     ` Sergei Shtylyov
2020-02-07 19:31       ` Dirk Behme
2020-02-07 20:17         ` Sergei Shtylyov
2020-02-10  9:18           ` Behme Dirk (CM/ESO2)
2020-02-18  4:00   ` Vignesh Raghavendra
2020-02-18  7:12     ` Behme Dirk (CM/ESO2)
2020-02-18 11:11       ` Vignesh Raghavendra
2020-02-20 18:30         ` Sergei Shtylyov
2020-02-24  5:27           ` Vignesh Raghavendra
2020-02-19 20:13     ` Sergei Shtylyov
2020-02-20  6:05       ` Vignesh Raghavendra
2020-02-20  7:46       ` Boris Brezillon
2020-02-20  7:49         ` Boris Brezillon [this message]

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