Re: [PATCH v3 1/1] mmc: dw_mmc: Add IDMAC 64-bit address mode support

[Arnd Bergmann <arnd@arndb.de>]

On Monday 19 August 2013, Prabu Thangamuthu wrote:
> 
> +#ifdef CONFIG_MMC_DW_IDMAC_64BIT_ADDRESS
> +       u32     des1;   /* Reserved */
> +
> +       u32     des2;   /* Buffer sizes */
> +#define IDMAC_SET_BUFFER1_SIZE(d, s) \
> +       ((d)->des2 = ((d)->des2 & 0x03ffe000) | ((s) & 0x1fff))
> +
> +       u32     des3;   /* Reserved */
> +
> +       u32     des4;   /* Lower 32-bits of Buffer Address Pointer 1*/
> +       u32     des5;   /* Upper 32-bits of Buffer Address Pointer 1*/
> +       u32     des6;   /* Lower 32-bits of Next Descriptor Address */
> +       u32     des7;   /* Upper 32-bits of Next Descriptor Address */
> +#else
>         u32             des1;   /* Buffer sizes */
>  #define IDMAC_SET_BUFFER1_SIZE(d, s) \
>         ((d)->des1 = ((d)->des1 & 0x03ffe000) | ((s) & 0x1fff))
> @@ -73,6 +86,7 @@ struct idmac_desc {
>         u32             des2;   /* buffer 1 physical address */
>  
>         u32             des3;   /* buffer 2 physical address */
> +#endif /* CONFIG_MMC_DW_IDMAC_64BIT_ADDRESS */

This is not a good idea: It means you cannot build the driver to support
both 32 and 64 bit at run-time. You have to remove all the #ifdef here
and replace it with runtime checks. You also need to update the binding
document to provide a way to detect which one is present in a given
system.

	Arnd