Re: [PATCH] mtd: brcmnand: set initial ECC params based on info from HW

[Brian Norris <computersforpeace@gmail.com>]

On Mon, Feb 01, 2016 at 10:09:28AM -0800, Florian Fainelli wrote:
> On 01/02/16 09:53, Brian Norris wrote:
> > Anyway, if we are really making the DT properties optional, we'd need to
> > modify Documentation/devicetree/bindings/mtd/brcm,brcmnand.txt to
> > reflect this.
> 
> The Marvell PXA3XX NAND controller has a "marvell,nand-keep-config"
> which seems to be in par with what Rafal is after here, maybe it would
> be worth standardizing/mimicing that kind of property for the brcmnand
> driver?

Maybe. Honestly, it's not that clear to me what the pxa3xx-nand binding
means. But if we make that clear, that could be a possibility.

(Side note: this isn't too far from what we did the Broadcom STB BSP
previously, except that we wouldn't use device tree. We attempted a
heuristic to detect whether the bootloader had initialized the flash
controller properly... I didn't want to maintain that crazy logic
upstream though. A DT flag to enable that behavior might be OK.)

> >> Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
> >> ---
> >> It took me hours to figure out how to setup NAND on my D-Link DIR-885L.
> >> This should be very helpful for ppl adding new devices support.
> > 
> > What if we just print out the hardware defaults when we bail out due to
> > missing ECC DT properties? Then developers can choose to set up their DT
> > with these properties, if those are actually proven correct. Would that
> > save you the hours of setup you mention?
> > 
> > Another option: maybe a commandline boot flag?
> 
> One could argue that the bootloader is patf of the platform, and so, if
> the bootloader is known to provide good defaults, then a DT property
> could be appropriate. The commandline boot flag just sounds a little
> impractical, in case you have more than one NAND controller, but how
> common is that?

Not sure if you mean multiple *controller* or multiple *flash*. The
former is much less common than the latter, but neither is very common
AFAIK.

Brian