[PATCH 4/5] [RFC] ARM: OMAP2+: gpmc: fix gpmc_hwecc_bch_capable

[Gupta, Pekon]

>From: Christoph Fritz [mailto:chf.fritz at googlemail.com]
>
>Most dt omap3 boards configure nand-ecc-opt as bch8. Due
>to lack of hardware elm support, bch8 software implementation
>gets set.
>
>Since commit 0611c41934ab35ce84dea "ARM: OMAP2+: gpmc: update
>gpmc_hwecc_bch_capable() for new platforms and ECC schemes",
>nand support stops working.
>
>This patch allows ecc software fallback.

Pleas add following tag at top of commit message.

Fixes: commit 0611c41934ab35ce84dea34ab291897ad3cbc7be
ARM: OMAP2+: gpmc: update gpmc_hwecc_bch_capable() for new platforms and ECC schemes

And please mark it for 3.15 stable if this gets accepted after 3.15-rcx.
Cc: <stable at vger.kernel.org> # 3.15.x+ 


>---
> arch/arm/mach-omap2/gpmc-nand.c |   16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
>diff --git a/arch/arm/mach-omap2/gpmc-nand.c b/arch/arm/mach-omap2/gpmc-nand.c
>index 4349e82..52c4834 100644
>--- a/arch/arm/mach-omap2/gpmc-nand.c
>+++ b/arch/arm/mach-omap2/gpmc-nand.c
>@@ -43,13 +43,17 @@ static struct platform_device gpmc_nand_device = {
> 	.resource	= gpmc_nand_resource,
> };
>
>-static bool gpmc_hwecc_bch_capable(enum omap_ecc ecc_opt)
>+static bool gpmc_ecc_bch_capable(enum omap_ecc ecc_opt)

I don't think this renaming is really required with this fix, so please
drop it and just keep it simple only for OMAP3 fix.


> {
> 	/* platforms which support all ECC schemes */
> 	if (soc_is_am33xx() || cpu_is_omap44xx() ||
> 		 soc_is_omap54xx() || soc_is_dra7xx())
> 		return 1;
>
>+	if ((ecc_opt == OMAP_ECC_BCH4_CODE_HW_DETECTION_SW) ||
>+		(ecc_opt == OMAP_ECC_BCH8_CODE_HW_DETECTION_SW))
>+		return 1;
>+

Note: Some very old legacy platforms have initial version of GPMC engine
which only supports Hamming ECC, and not BCH ECC scheme, so lets
filter them out to maintain backward compatibility.

(1) As per TRM, OMAP2 platform does not support BCH ECC schemes,
      So please filter out OMAP2 devices from this check ...

(2) I don't know the history but below comment says:
"* For now, assume 4-bit mode is only supported on OMAP3630 ES1.x, x>=1"

if ((ecc_opt == OMAP_ECC_BCH4_CODE_HW_DETECTION_SW) ||
	 (ecc_opt == OMAP_ECC_BCH8_CODE_HW_DETECTION_SW))  {
	if (cpu_is_omap24xx())
		return 0;
	else if (cpu_is_omap3630() && (GET_OMAP_REVISION() == 0))
		return 0;
	else
		return 1;
}


> 	/* OMAP3xxx do not have ELM engine, so cannot support ECC schemes
> 	 * which require H/W based ECC error detection */
> 	if ((cpu_is_omap34xx() || cpu_is_omap3630()) &&
>@@ -57,14 +61,6 @@ static bool gpmc_hwecc_bch_capable(enum omap_ecc ecc_opt)
> 		 (ecc_opt == OMAP_ECC_BCH8_CODE_HW)))
> 		return 0;
>
>-	/*
>-	 * For now, assume 4-bit mode is only supported on OMAP3630 ES1.x, x>=1
>-	 * and AM33xx derivates. Other chips may be added if confirmed to work.
>-	 */
>-	if ((ecc_opt == OMAP_ECC_BCH4_CODE_HW_DETECTION_SW) &&
>-	    (!cpu_is_omap3630() || (GET_OMAP_REVISION() == 0)))
>-		return 0;
>-
Thanks for removing this, I too wasn't confident of this either.


> 	/* legacy platforms support only HAM1 (1-bit Hamming) ECC scheme */
> 	if (ecc_opt == OMAP_ECC_HAM1_CODE_HW)
> 		return 1;
>@@ -140,7 +136,7 @@ int gpmc_nand_init(struct omap_nand_platform_data *gpmc_nand_data,
>
> 	gpmc_update_nand_reg(&gpmc_nand_data->reg, gpmc_nand_data->cs);
>
>-	if (!gpmc_hwecc_bch_capable(gpmc_nand_data->ecc_opt)) {
>+	if (!gpmc_ecc_bch_capable(gpmc_nand_data->ecc_opt)) {

Please drop this renaming from this patch.

> 		dev_err(dev, "Unsupported NAND ECC scheme selected\n");
> 		return -EINVAL;
> 	}
>--
>1.7.10.4

You may send this patch separately apart from the series, so that
this gets accepted in current 3.15-rcx.

with regards, pekon