RE: [PATCH v3 4/4] ARM: OMAP: gpmc: add DT bindings for GPMC timings and NAND

From: "Philip, Avinash" <avinashphilip@ti.com>
To: Daniel Mack <zonque@gmail.com>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"paul@pwsan.com" <paul@pwsan.com>,
	"Mohammed, Afzal" <afzal@ti.com>,
	"devicetree-discuss@lists.ozlabs.org"
	<devicetree-discuss@lists.ozlabs.org>,
	"Nori, Sekhar" <nsekhar@ti.com>,
	"tony@atomide.com" <tony@atomide.com>,
	"Hunter, Jon" <jon-hunter@ti.com>,
	"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>
Subject: RE: [PATCH v3 4/4] ARM: OMAP: gpmc: add DT bindings for GPMC timings and NAND
Date: Wed, 7 Nov 2012 15:37:02 +0000	[thread overview]
Message-ID: <518397C60809E147AF5323E0420B992E3E9DE420@DBDE01.ent.ti.com> (raw)
In-Reply-To: <509A2E75.5060307@gmail.com>

On Wed, Nov 07, 2012 at 15:18:37, Daniel Mack wrote:
> On 05.11.2012 14:29, Philip, Avinash wrote:
> > On Mon, Nov 05, 2012 at 18:28:22, Daniel Mack wrote:
> >> On 05.11.2012 12:03, Philip, Avinash wrote:
> >>> On Fri, Nov 02, 2012 at 20:55:56, Daniel Mack wrote:
> >>>> This patch adds basic DT bindings for OMAP GPMC.
> >>>>
> >>>> The actual peripherals are instanciated from child nodes within the GPMC
> >>>> node, and the only type of device that is currently supported is NAND.
> >>>>
> >>>> Code was added to parse the generic GPMC timing parameters and some
> >>>> documentation with examples on how to use them.
> >>>>
> >>>> Successfully tested on an AM33xx board.
> >>>>
> >>>> Signed-off-by: Daniel Mack <zonque@gmail.com>
> >>> [...]
> >>>> +
> >>>> +		nand@0,0 {
> >>>> +			reg = <0 0 0>; /* CS0, offset 0 */
> >>>> +			nand-bus-width = <16>;
> >>>> +			nand-ecc-mode = "none";
> >>>> +
> >>>> +			gpmc,sync-clk = <0>;
> >>>> +			gpmc,cs-on = <0>;
> >>>> +			gpmc,cs-rd-off = <36>;
> >>>> +			gpmc,cs-wr-off = <36>;
> >>>> +			gpmc,adv-on = <6>;
> >>>> +			gpmc,adv-rd-off = <24>;
> >>>> +			gpmc,adv-wr-off = <36>;
> >>>> +			gpmc,we-off = <30>;
> >>>> +			gpmc,oe-off = <48>;
> >>>> +			gpmc,access = <54>;
> >>>> +			gpmc,rd-cycle = <72>;
> >>>> +			gpmc,wr-cycle = <72>;
> >>>> +			gpmc,wr-access = <30>;
> >>>> +			gpmc,wr-data-mux-bus = <0>;
> >>>> +
> >>>> +			#address-cells = <1>;
> >>>> +			#size-cells = <1>;
> >>>> +
> >>>
> >>> Can you take the timings (for example) from arago tree. The timings is tested in am335x-evm
> >>> So the timings can be directly used to populate GPMC timings. Timings can found at
> >>>
> >>> http://arago-project.org/git/projects/?p=linux-am33x.git;a=commitdiff;
> >>> h=66bfbd2c5b35dc81edce0c24843c476161ab5978;hp=370630359cb8db711cf0941cd2a242e28ccfb61e
> >>>
> >>> [...]
> >>>> +static int gpmc_probe_dt(struct platform_device *pdev)
> >>>
> >>> Can you take care of the following section mismatch.
> >>> WARNING: vmlinux.o(.text+0x1e2d0): Section mismatch in reference
> >>> from the function gpmc_probe_dt() to the function .init.text:gpmc_nand_init().
> >>
> >> Sore, both fixed for v4.
> >>
> >>> [...]
> >>>> +
> >>>> +		val = of_get_nand_ecc_mode(child);
> >>>> +		if (val >= 0)
> >>>> +			gpmc_nand_data->ecc_opt = val;
> >>>
> >>> This will fail for BCH. Index of "soft_bch" is 5 & also don't have selection
> >>> option between for BCH4 & BCH8 also.
> >>> Can you use the of_property_read_u32 (as done early) to pass the ecc selection
> >>> from dt file. This will help selection of BCH4 & BCH8 ecc options.
> >>
> >> Hmm. Shouldn't we rather teach of_get_nand_ecc_mode() that two modes and
> >> bring the enum in sync?
> > 
> > ecc_opt is for selecting different ecc layout and not for selecting ecc mode.
> > 
> > In omap2 driver NAND_ECC_HW ecc mode supports 3 ecc layout
> > 	OMAP_ECC_HAMMING_CODE_HW_ROMCODE
> > 	OMAP_ECC_BCH4_CODE_HW
> > 	OMAP_ECC_BCH8_CODE_HW
> > 
> > So selection of ecc layout data should come from DT not ecc mode.
> 
> Ok, I see. I would still like to set them by string rather than magic
> numbers that map to enum entries. Valid values would be "none", "hw",
> "hw-romcode", "bch4" and "bch8". Are you ok with that?

Ok, that's nice. Better use ecc_opt instead of ecc_mode.

Thanks
Avinash

> 
> 
> Thanks,
> Daniel
> 
> 