[U-Boot] [PATCH 1/1] am33xx: add CONFIG_SYS_NAND_DEVICE_WIDTH to determine NAND device bus-width

[Gupta, Pekon]

Hi,

Please see last set of queries inline..

> From: Scott Wood [mailto:scottwood at freescale.com]
> > On Sat, 2013-09-28 at 06:24 +0000, Gupta, Pekon wrote:
> > > From: Scott Wood [mailto:scottwood at freescale.com]
> > > > On Fri, 2013-09-27 at 04:18 +0000, Gupta, Pekon wrote:
[snip]
> > >
> > (1) drivers/mtd/nand/fsl_ifc_spl.c
> > (2) drivers/mtd/nand/fsl_elbc_spl.c
> > So CONFIG_SYS_NAND_DEVICE_WIDTH should help them also. right ?
> 
> How would it help?
> 
I meant, instead of requiring the modification in board file,
CONFIG_SPL_DEVICE_WIDTH can be put in include/configs/*.h

> > So can this new CONFIG_xx be accepted ?
> 
> Only for SPL usage.
> 
Ok. so should I rename to CONFIG_SPL_NAND_DEVICE_WIDTH ?

I have recently sent another version of this patch (as PATCH 2/4) of
series below. This series also adds checks for reading ONFI params.
Request you to review that also, so that I can include all feedbacks in
next patch version.
http://lists.denx.de/pipermail/u-boot/2013-September/163878.html


> > > > > It looked
> > > > > like you were removing the code that does dynamic detection, which
> > > would
> > > > > also affect non-SPL.
> > > > >
> > > > >  > -	/* If we are 16 bit dev, our gpmc config tells us that */
> > > > > >  -	if ((readl(&gpmc_cfg->cs[cs].config1) & 0x3000) == 0x1000)
> > > >
> > > > omap_gpmc.c never had dynamic detection support. Above
> gpmc_config
> > > bit
> > > > which is used to tell whether device is x16 or x8, gets actually hard-
> coded in
> > > > gpmc_init(). Thus it was actually a mechanism to pass hard-coded bus-
> > > width
> > > > information to nand driver.
> > > > Refer: arch/arm/cpu/armv7/am33xx/mem.c : gpmc_init()
> > > >
> > > > So, instead of hacking the gpmc_init() everytime for different devices,
> > > > this patch introduces a generic CONFIG which can be used everywhere.
> > >
Re-added dynamic detection for u-boot (second stage) in above series.
CONFIG_SPL_NAND_DEVICE_WIDTH would be used only for SPL boot.
http://lists.denx.de/pipermail/u-boot/2013-September/163879.html


> > > It looks like you do more NAND config in gpmc_init() than just setting
> > > this one bit, so I don't think you save anything here.
> > >
> > > BTW, do you not need to set this bit in the config register for the
> > > hardware to work in the SPL case?
> > >
> > Yes, I'm not changing the default configs for GPMC in gpmc_init(),
> > because they are ok for x8 device. I'm just overriding them again during
> > board_nand_init() if CONFIG_SYS_NAND_DEVICE_WIDTH == x16 device.
> 
> Is this due to wanting to do identification as x8?
> 
Yes, reading of on-chip ONFI params should happen only in x8 mode.
[PATCH 1/4] of above series should explain this.
http://lists.denx.de/pipermail/u-boot/2013-September/163882.html

(dropping few emails from CC list as they are bouncing,
and u-boot mailman rejects email saying too many recipients).

with regards, pekon