On Sat, 2013-09-28 at 06:24 +0000, Gupta, Pekon wrote:
From: Scott Wood [mailto:scottwood@freescale.com]
On Fri, 2013-09-27 at 04:18 +0000, Gupta, Pekon wrote:
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.
Unlikely, given that they've all managed to work without this so far. E.g. eLBC and IFC hardcode this information on a per-chip basis in the #defines that hold values for config registers, and prior to this patch omap_gpmc had code to read a config register (regardless of where it originally got set).
(1) drivers/mtd/nand/fsl_ifc_spl.c They are doing same way as OMAP used to. They are also using controller configurations to tell driver about the]NAND bus-width "port_size = (cspr & CSPR_PORT_SIZE_16) ? 16 : 8;"
Yes. Note that CSPR is set per-chip.
(2) drivers/mtd/nand/fsl_elbc_spl.c They are doing incomplete check. Rather they are not caring for x16 device
Right, I forgot that eLBC doesn't support 16-bit NAND (hardware limitation).
So CONFIG_SYS_NAND_DEVICE_WIDTH should help them also. right ?
How would it help?
So can this new CONFIG_xx be accepted ?
Only for SPL usage.
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.
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?
-Scott