[PATCH v5 4/4] ARM: OMAP: gpmc: add DT bindings for GPMC timings and NAND

[Philip, Avinash]

On Thu, Nov 29, 2012 at 18:11:42, Daniel Mack wrote:
> On 29.11.2012 13:36, Philip, Avinash wrote:
> > On Wed, Nov 28, 2012 at 22:28:59, Daniel Mack wrote:
> > [...]
> >> +	if (!of_property_read_string(child, "ti,nand-ecc-opt", &s)) {
> >> +		for (val = 0; val < ARRAY_SIZE(nand_ecc_opts); val++)
> >> +			if (!strcasecmp(s, nand_ecc_opts[val])) {
> >> +				gpmc_nand_data->ecc_opt = val;
> >> +				break;
> >> +			}
> >> +
> >> +		/*
> >> +		 *  AM335x RBL compatibility mode - dependns on runtime
> >> +		 * detection of the error location module.
> >> +		 */
> >> +		if (!strcasecmp(s, "bch8-am335xrbl-compatible")) {
> >> +			gpmc_nand_data->ecc_opt = OMAP_ECC_BCH8_CODE_HW;
> >> +			gpmc_nand_data->is_elm_used = true;
> > 
> > Remove is_elm_used from struct omap_nand_platform_data. Now this data
> > populated as part of run time detection of elm module. So please remove
> > The usage of is_elm_used;
> 
> So why do we need "bch8-am335xrbl-compatible" as special case then?
> 
> I thought the whole idea here is to tell the driver we want bch8 *and*
> the usage of the elm, instead of falling back to the (incompatible)
> software mode? If I remove that assignment, "bch8-am335xrbl-compatible"
> is the same than "bch8".
> 

Here we have different problems present. 
1. GPMC-NAND DT binding support.
2. Compatible ECC layout between kernel, boot loader.
3. Support for hardware accelerator, i.e ELM for error correction.

So priority should go for GPMC DT binding support. 
Can you please proceed with GPMC-NAND DT bindings without considering
ELM so that driver features existing can be obtained with DT.

I will take care of ECC layout (or RBL) compatibility along with ELM
series. I will make ELM series on top of your changes. This way we can
avoid circular dependency

>
> Which detail am I missing? :)

I think what you need is NAND ECC layout to be common across Kernel and
boot loader. Strictly speaking ELM is not a necessity for it. The common
layout can be obtained even without presence of ELM, ELM is only a hardware
accelerator for error correction. If ELM is not used, we can rely on software
error correction, at least theoretically. But the way software error correction
is handled currently in omap nand driver will not help us as ecc layout assumed
is different.

Thanks
Avinash

> 
> 
> Daniel
> 
>