linux-kernel - Re: [PATCH] Add spi-nor driver for Realtek RTL838x/RTL839x switch SoCs

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Date:   Wed, 16 Dec 2020 19:15:47 +0800
From:   Chuanhong Guo <gch981213@...il.com>
To:     Tudor Ambarus <Tudor.Ambarus@...rochip.com>
Cc:     bert@...t.com, Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>, john.garry@...wei.com,
        Boris Brezillon <bbrezillon@...nel.org>,
        vadivel.muruganx.ramuthevar@...ux.intel.com,
        open list <linux-kernel@...r.kernel.org>,
        linux-mtd@...ts.infradead.org
Subject: Re: [PATCH] Add spi-nor driver for Realtek RTL838x/RTL839x switch SoCs

Hi!

On Wed, Dec 16, 2020 at 4:30 PM <Tudor.Ambarus@...rochip.com> wrote:
>
> On 12/15/20 11:46 PM, Bert Vermeulen wrote:
> > This driver supports the spiflash core in all RTL838x/RTL839x SoCs,
> > and likely some older models as well (RTL8196C).
> >
> Can we use SPIMEM and move this under drivers/spi/ instead?
>
> Cheers,
> ta

Just took a brief look at the code, and here's my current understanding
of this controller:
1. CS is controlled separately with SFCSR_CSB* bits
2. To write 1-4 bytes, set SFCSR_LEN* and write to SFDR
2. To read 1-4 bytes, set SFCSR_LEN* and read SFDR

If that's true, this is a generic half-duplex spi controller, and the driver
should register a spi_controller with set_cs and transfer_one
implemented.

-- 
Regards,
Chuanhong Guo