[U-Boot] [PATCH] fdt: Allow fdt_translate_address() to work with buses

[Przemyslaw Marczak]

Hello Simon,

On 01/04/2016 12:04 AM, Simon Glass wrote:
> It is common for I2C and SPI buses to have a single-cell address and a size
> of 0. These produce a warning at present. For example on snow:
>
> __of_translate_address: Bad cell count for gpc4
> __of_translate_address: Bad cell count for gpx0
> __of_translate_address: Bad cell count for gpv2
> __of_translate_address: Bad cell count for gpv4
>
> One of the nodes in question looks like this in part:
>
> 	pinctrl_2: pinctrl at 10d10000 {
> 		#address-cells = <1>;
> 		#size-cells = <0>;
> 		gpv2: gpv2 {
> 			reg = <0x060>;
> 		};
> 		gpv4: gpv4 {
> 			reg = <0xc0>;
> 		};
> 	};
>
> This is clearly valid so it looks like the conversion to use
> fdt_translate_address() in dev_get_addr() is not currently a good move.
>
> Przemyslaw Marczak sent three patches to resolve this for exynos boards:
>
> https://patchwork.ozlabs.org/patch/557008/
> https://patchwork.ozlabs.org/patch/557010/
> https://patchwork.ozlabs.org/patch/557009/
>
> But this involves creating a new function, and everyone will need to know
> when to use which one. Also the problem may affect other boards.
>
> Instead we can relax the contraint that there must be at least one size
> cell. This fixes the problem on snow and should not affect anything else,
> since the error check should not fire on normal device trees anyway.
>
> After the release we will have more time to come up with a better solution,
> if one exists.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>   common/fdt_support.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/common/fdt_support.c b/common/fdt_support.c
> index 66464db..43c5fa8 100644
> --- a/common/fdt_support.c
> +++ b/common/fdt_support.c
> @@ -952,8 +952,7 @@ void fdt_del_node_and_alias(void *blob, const char *alias)
>   /* Max address size we deal with */
>   #define OF_MAX_ADDR_CELLS	4
>   #define OF_BAD_ADDR	FDT_ADDR_T_NONE
> -#define OF_CHECK_COUNTS(na, ns)	((na) > 0 && (na) <= OF_MAX_ADDR_CELLS && \
> -			(ns) > 0)
> +#define OF_CHECK_COUNTS(na, ns)	((na) > 0 && (na) <= OF_MAX_ADDR_CELLS)
>
>   /* Debug utility */
>   #ifdef DEBUG
>

The patch with this fix was send by me some time ago:

https://patchwork.ozlabs.org/patch/537372/

It actually do the same, what your patch does.

And my next three patches (adding dev_get_reg()), which you mentioned, 
are another way to fix the issue.

So I think, we should choose between those two ways.

However the first one breaks the consistency with the kernel:

drivers/of/address.c: __of_translate_address()

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com