Re: [PATCH v2 0/5] mtd: spi-nor: Add support for Octal 8D-8D-8D mode

From: masonccyang@mxic.com.tw
To: "Pratyush Yadav" <me@yadavpratyush.com>
Cc: "Boris Brezillon" <boris.brezillon@collabora.com>,
	broonie@kernel.org, juliensu@mxic.com.tw,
	linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
	linux-spi@vger.kernel.org, miquel.raynal@bootlin.com,
	"Pratyush Yadav" <p.yadav@ti.com>,
	richard@nod.at, tudor.ambarus@microchip.com, vigneshr@ti.com
Subject: Re: [PATCH v2 0/5] mtd: spi-nor: Add support for Octal 8D-8D-8D mode
Date: Fri, 15 May 2020 10:26:05 +0800	[thread overview]
Message-ID: <OF03B5329E.56965A70-ON48258569.000878CE-48258569.000D5FFD@mxic.com.tw> (raw)
In-Reply-To: <20200506094028.2asq56goslfd2ngo@yadavpratyush.com>

Hi Pratyush,

> > > > I can't apply your patches to enable xSPI Octal mode for 
> > > > mx25uw51245g because your patches set up Octal protocol first and 
> > > > then using Octal protocol to write Configuration Register 2(CFG 
> > > > Reg2). I think driver
> > > > should write CFG Reg2 in SPI 1-1-1 mode (power on state) and make 
sure
> > > > write CFG Reg 2 is success and then setup Octa protocol in the 
last.
> > > 
> > > Register writes should work in 1S mode, because nor->reg_proto is 
only 
> > > set _after_ 8D mode is enabled (see spi_nor_octal_dtr_enable()). In 
> > > fact, both patch 15 and 16 in my series use register writes in 1S 
mode.
> > 
> > but I didn't see driver roll back "nor->read/write_proto = 1" 
> > if xxx->octal_dtr_enable() return failed!
> 
> I copied what spi_nor_quad_enable() did, and made failure fatal. So if 
> xxx->octal_dtr_enable() fails, the probe would fail and the flash would 
> be unusable. You can try your hand at a fallback system where you try 

IMHO, it's not a good for system booting from SPI-NOR, 
driver should still keep system alive in SPI 1-1-1 mode in case of 
enable Octal/Quad failed.

Therefore, my patches is to setup nor->read/write_proto = 8 in case 
driver enable Octal mode is success. And to enable Octal mode in
spi_nor_late_init_params()rather than as spi_nor_quad_enable()did.

> all possible protocols available, but I think that should be a different 

> patchset.
> 
> -- 
> Regards,
> Pratyush Yadav

thanks & best regards,
Mason

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