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Date: Wed, 9 Jan 2019 23:05:25 +0100
From: Boris Brezillon <bbrezillon@kernel.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: David Woodhouse <dwmw2@infradead.org>, Brian Norris
 <computersforpeace@gmail.com>, Marek Vasut <marek.vasut@gmail.com>, Richard
 Weinberger <richard@nod.at>, linux-mtd@lists.infradead.org
Subject: Re: [PATCH] mtd: rawnand: fsmc: Keep CE enabled fix mb() drain
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On Wed, 9 Jan 2019 22:40:22 +0100
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Wed, Jan 9, 2019 at 10:21 PM Boris Brezillon <bbrezillon@kernel.org> wrote:
> > On Wed,  9 Jan 2019 21:55:30 +0100
> > Linus Walleij <linus.walleij@linaro.org> wrote:  
> 
> > > This patch keeps the CE (chip enable, the only chip select)
> > > signal from the FSMC block enabled from the first command
> > > after probe() or resume() until the driver either suspend()
> > > or remove(). Create a state variable to track this.  
> >
> > I just read the Spear600 reference manual, and I'm not sure the
> > BANK_ENABLE bit controls the CE line. My understanding is that it just
> > marks the bank as active and CE line is asserted when you actually
> > access the AHB mem bank range (probably after making sure the FSMC bus
> > is idle).  
> 
> The Nomadik STn8815 says (for this bit):
> 
> PBKEN PC-card/NAND-Flash chip-select enable.
> Enables the corresponding chip-select.
> If a disabled chip-select is accessed, an HRESP = ERROR is generated
> on the AHB bus.
> 0: disabled (default after reset)
> 1: enabled
> 
> The same for Nomadik STn8820 and the Ux500 variants.
> 
> So "enable" might very well have the meaning you say above,
> it's just very unclear and confusing.
> 
> > If I'm correct, I'd recommend dropping fsmc_ce_ctrl() and marking the
> > bank enabled at probe time.  
> 
> This already happens in fsmc_nand_setup() so we just
> need to delete some code then.
> 
> But maybe we should disable it during remove()
> at least?

Yep, and set it again at resume time, just in case regs content is lost
at suspend time.