From: Scott Wood [mailto:scottwood@freescale.com]
On Thu, 2013-09-26 at 13:14 +0000, Gupta, Pekon wrote:
From: Gupta, Pekon pekon@ti.com
NAND driver needs to know bus-width of the connected NAND device,
in
order to perform proper I/O and initialize itself. Currently there is no
CONFIG
option to provide this information to NAND driver.
- SPL NAND driver does not have framework to parse ONFI parameter
page.
Is this about SPL? It looks like a more general change.
Yes, actually I would have loved to see a generic SPL driver for all platforms,
How could that possibly work?
NAND SPL (as in drivers/mtd/nand/am335x_spl_bch.c) had following limitation (a) depends on CONFIG_SYS_NAND_xx (for NAND device parameters like erasesize, pagesize, oobsize, etc). (b) can only do NAND read access. (c) calls nand_chip->ecc.hwctl() for doing controller specific configurations, which is populated while doing board_nand_init().
Above (a), (b), and (c) do not have any SoC specific dependency. And can be put into a generic framework which can be used for all SPL drivers.
All SoC specific configurations are done in either: - board_nand_init(): initializations based on device. - nand_chip->ecc.hwctl(): configurations for ECC scheme. which is *shared* code between SPL & u-boot driver, and is present in u-boot driver file (like drivers/mtd/nand/omap_gpmc.c), not in SPL driver file.
The missing piece was device bus-width detection which I addresses in this patch by adding CONFIG_SYS_NAND_DEVICE_WIDTH.
because SPL is mostly statically configured, and it just does plain NAND read (it doesn’t even support NAND write, etc). But I do not know the hardware configurations tweaks of other SoC, So at-least have common CONFIG_SYS_NAND_xx which all SPL drivers can
use.
Again, are you introducing this symbol for use only in SPL?
Apart from SPL, CONFIG_SYS_NAND_DEVICE_WIDTH also be useful for (1) drivers which do not use CONFIG_SYS_NAND_ONFI_DETECTION, where code for reading on-chip ONFI parameters is not enabled in nand_base.c (2) non ONFI compatible NAND devices.
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.
I have sent this patch separately to see the acceptance of new generic CONFIG_SYS_NAND_DEVICE_WIDTH. If this gets accepted, then I'll resend the patch-series which actually does dynamic detection.. http://lists.denx.de/pipermail/u-boot/2013-September/162295.html http://lists.denx.de/pipermail/u-boot/2013-September/162296.html
(dropping others in CC list as u-boot maillist rejects the mail saying too many recipients. !! )
with regards, pekon