linux-kernel - Re: [RFC] spi: dw: support setting tmode dynamically

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Date:	Tue, 5 Jan 2016 16:12:31 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Jisheng Zhang <jszhang@...vell.com>
Cc:	linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] spi: dw: support setting tmode dynamically

On Wed, Dec 23, 2015 at 08:29:52PM +0800, Jisheng Zhang wrote:
> On Wed, 23 Dec 2015 12:15:12 +0000 Mark Brown wrote:
> > On Wed, Dec 23, 2015 at 07:23:38PM +0800, Jisheng Zhang wrote:

> > > Currently the spi-dw tmode is fixed to SPI_TMOD_TR if cs_control is NULL, but we
> > > need to set it as SPI_TMOD_EPROMREAD to read nor flash, my solution is to add and
> > > export one functions to set the tmode, then the nor flash driver call it
> > > before reading and set back to SPI_TMOD_TR after done.  

> > What does this mean - what is TMOD and why do we need to set it to read
> > NOR flash?  I've no information on this controller...

> TMOD is one field of DW_SPI_CTRL0. Its available value could be:

> 0: Transmit and Receive
> 1: Transmit only
> 2: Receive only
> 3: EEPROM Read

> If the one spi nor flash is connected to the SPI host, so far I can only succeed
> to read the nor flash content after setting the TMOD field as 3.

Why?  What does this mean in practical terms at the hardware level, what
is "EEPROM read"?  It sounds like there's some bigger issue here.

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