[U-Boot] [PATCH] mtd: nand: mxs: fix PIO_WORD number

[Marek Vasut <marex@denx.de>]

On Friday, December 12, 2014 at 01:43:22 PM, Stefan Roese wrote:
> Hi Luca,
> 
> On 12.12.2014 13:40, Luca Ellero wrote:
> >> On 10.12.2014 09:24, Luca Ellero wrote:
> >>> There is only one pio_word in this DMA transaction so data field must
> >>> be 1.
> >>> 
> >>> Signed-off-by: Luca Ellero <luca.ellero@brickedbrain.com>
> >>> ---
> >>> 
> >>>   drivers/mtd/nand/mxs_nand.c |    2 +-
> >>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>> 
> >>> diff --git a/drivers/mtd/nand/mxs_nand.c b/drivers/mtd/nand/mxs_nand.c
> >>> index 7a064ab..616c9ca 100644
> >>> --- a/drivers/mtd/nand/mxs_nand.c
> >>> +++ b/drivers/mtd/nand/mxs_nand.c
> >>> @@ -305,7 +305,7 @@ static void mxs_nand_cmd_ctrl(struct mtd_info
> >>> *mtd, int data, unsigned int ctrl)
> >>> 
> >>>       d->cmd.data =
> >>>       
> >>>           MXS_DMA_DESC_COMMAND_DMA_READ | MXS_DMA_DESC_IRQ |
> >>>           MXS_DMA_DESC_CHAIN | MXS_DMA_DESC_DEC_SEM |
> >>> 
> >>> -        MXS_DMA_DESC_WAIT4END | (3 << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
> >>> +        MXS_DMA_DESC_WAIT4END | (1 << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
> >>> 
> >>>           (nand_info->cmd_queue_len << MXS_DMA_DESC_BYTES_OFFSET);
> >> 
> >> What error or problem does this incorrect setup cause in your case? I'm
> >> asking since I'm also using this driver in some mx6 system and have not
> >> seen any issues.
> > 
> > As far as I can see, it doesn't seem to cause any issue. But, if you
> > read the iMX6 Reference Manual (chapter 14.2) this field should reflect
> > the number of PIO_WORDS appended to the DMA command, in this case 1.
> 
> Okay. I just wanted to check if this patch fixes a real problem that you
> have experienced. Thanks for the explanation.
> 
> Reviewed-by: Stefan Roese <sr@denx.de>

The patch does in fact change the behavior such that it no longer clears the 
ECCCTRL and COMPARE registers both on MX28 and on MX6 . Could this have some 
impact?

Best regards,
Marek Vasut