[U-Boot] [PATCHv2 1/3] nand_spl_simple: Add a simple flash read function

[Scott Wood <oss@buserror.net>]

On Mon, 2016-01-04 at 16:54 +0100, Ladislav Michl wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> To support UBI in SPL we need a simple flash read function. Add one to
> nand_spl_simple and keep it as simple as it goes.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Where is your signoff?

Did Thomas really write this patch for U-Boot (if so, why isn't he on CC?) or
is it taken from some other project?

> ---
>  drivers/mtd/nand/nand_spl_simple.c | 64
> ++++++++++++++++++++++++++++++++++++++
>  include/nand.h                     |  1 +
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/mtd/nand/nand_spl_simple.c
> b/drivers/mtd/nand/nand_spl_simple.c
> index e69f662..2e1af53 100644
> --- a/drivers/mtd/nand/nand_spl_simple.c
> +++ b/drivers/mtd/nand/nand_spl_simple.c
> @@ -209,6 +209,70 @@ static int nand_read_page(int block, int page, void
> *dst)
>  }
>  #endif
>  
> +#ifdef CONFIG_SPL_UBI
> +/*
> + * Temporary storage for non NAND page aligned and non NAND page sized
> + * reads. Note: This does not support runtime detected FLASH yet, but
> + * that should be reasonably easy to fix by making the buffer large
> + * enough :)
> + */
> +static u8 scratch_buf[CONFIG_SYS_NAND_PAGE_SIZE];
> +
> +/**
> + * nand_spl_read_flash - Read data from flash into a buffer
> + * @pnum:	Number of the physical eraseblock

s/pnum/block/g

> + * @offset:	Data offset from the start of @pnum
> + * @len:	Data size to read
> + * @dest:	Address of the destination buffer
> + *
> + * This could be further optimized if we'd have a subpage read
> + * function in the simple code. On NAND which allows subpage reads
> + * this would spare quite some time to readout e.g. the VID header of
> + * UBI.
> + *
> + * Notes:
> + *
> + *	@offset + @len are not allowed to be larger than a physical
> + *	erase block. No sanity check done for simplicity reasons.
> + *
> + * To support runtime detected flash this needs to be extended by
> + * information about the actual flash geometry, but thats beyond the
> + * scope of this effort and for most applications where fast boot is
> + * required its a non issue anyway.
> + */
> +int nand_spl_read_flash(u32 pnum, u32 offset, u32 len, void *dest)

This name is too generic and doesn't suggest what's different compared to
nand_spl_load_image (they both read data from flash into a buffer).

How about nand_spl_read_block()?

> +{
> +	u32 offs, page, read, toread = len;
> +
> +	/* Calculate the page number */
> +	page = offset / CONFIG_SYS_NAND_PAGE_SIZE;
> +
> +	/* Offset to the start of a flash page */
> +	offs = offset % CONFIG_SYS_NAND_PAGE_SIZE;
> +
> +	while (toread) {
> +		/*
> +		 * Non page aligned reads go to the scratch buffer.
> +		 * Page aligned reads go directly to the destination.
> +		 */
> +		if (offs || toread < CONFIG_SYS_NAND_PAGE_SIZE) {
> +			nand_read_page(pnum, page, scratch_buf);
> +			read = min(len, toread);

toread is always <= len, so this is pointless.  As this is the only use of len
after the toread init, once this is gone you could also eliminate toread and
just use len.

-Scott