[Skiboot] [RFC PATCH 3/3] libflash: add flash_erase_corrected() to set ECC bytes in erased areas

[Michael Neuling]

On Thu, 2015-03-05 at 20:39 +1100, Cyril Bur wrote:
> From: Cyril Bur <cyril.bur at au1.ibm.com>
> 
> Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
> ---
>  libflash/libflash.c | 32 ++++++++++++++++++++++++++++++++
>  libflash/libflash.h |  1 +
>  2 files changed, 33 insertions(+)
> 
> diff --git a/libflash/libflash.c b/libflash/libflash.c
> index cae62ec..84a78f6 100644
> --- a/libflash/libflash.c
> +++ b/libflash/libflash.c
> @@ -309,6 +309,38 @@ int flash_erase(struct flash_chip *c, uint32_t dst, uint32_t size)
>  	return 0;
>  }
>  
> +int flash_erase_corrected(struct flash_chip *c, uint32_t dst, uint32_t size, bool ecc)
> +{
> +
> +	int rc = flash_erase(c, dst, size);
> +
> +	if (rc == 0 && ecc) {
> +		uint32_t i;
> +		uint8_t zero = 0;
> +
> +		/*
> +		 * We have just erased this region which means it will be all FF.
> +		 * The ECC byte for that is 00 so the easiest way to deal is just to
> +		 * write 00 every 9th byte.
> +		 * Really should optimise this.
> +		 */
> +
> +		/* Align dst, probably already is but best to be sure */
> +		if (dst & 0x7) {
> +			dst &= ~0x7UL;
> +			dst += 8;
> +		}

This alignment doesn't seem like the right thing to do.  If I passed in
a dst pointer, I wouldn't expect this function to align it for me.  

Why not reuse your packed struct ecc64 here again and avoid the magic "+
9" maths.

Thanks for fixing this.

Mikey

> +
> +		i = 9;
> +		while (rc == 0 && i < size) {
> +			rc = flash_write(c, dst + i, &zero, 1, 0);
> +			i += 9;
> +		}
> +	}
> +
> +	return rc;
> +}
> +
>  int flash_erase_chip(struct flash_chip *c)
>  {
>  	struct spi_flash_ctrl *ct = c->ctrl;
> diff --git a/libflash/libflash.h b/libflash/libflash.h
> index 51584da..f7ca205 100644
> --- a/libflash/libflash.h
> +++ b/libflash/libflash.h
> @@ -74,6 +74,7 @@ int flash_read(struct flash_chip *c, uint32_t pos, void *buf, uint32_t len);
>  int flash_read_corrected(struct flash_chip *c, uint32_t pos, void *buf,
>  		uint32_t len, bool ecc);
>  int flash_erase(struct flash_chip *c, uint32_t dst, uint32_t size);
> +int flash_erase_corrected(struct flash_chip *c, uint32_t dst, uint32_t size, bool ecc);
>  int flash_write(struct flash_chip *c, uint32_t dst, const void *src,
>  		uint32_t size, bool verify);
>  int flash_write_corrected(struct flash_chip *c, uint32_t dst, const void *src,