Re: [PATCH] mtd: rawnand: fsmc: Keep CE enabled fix mb() drain

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Wed, Jan 9, 2019 at 10:21 PM Boris Brezillon <bbrezillon@xxxxxxxxxx> wrote:
> On Wed,  9 Jan 2019 21:55:30 +0100
> Linus Walleij <linus.walleij@xxxxxxxxxx> 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?

Yours,
Linus Walleij

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