linux-kernel - Re: [PATCH v2 09/19] ARM: at91: make sdram/ddr register base soc independent

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Date:	Thu, 23 Feb 2012 21:51:46 +1100
From:	Ryan Mallon <rmallon@...il.com>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
CC:	plagnioj@...osoft.com, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 09/19] ARM: at91: make sdram/ddr register base soc
 independent

On 23/02/12 20:58, Nicolas Ferre wrote:

> On 02/23/2012 09:56 AM, Nicolas Ferre :
>> On 02/22/2012 11:33 PM, Ryan Mallon :
>>> On 22/02/12 20:39, Nicolas Ferre wrote:
>>>
>>>> From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
>>>>
>>>> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
>>>> Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
>>>> ---
>>>
>>> <snip>
>>>
>>>> +void __init at91_ioremap_ramc(int id, u32 addr, u32 size)
>>>> +{
>>>> +	if (id > 1) {
>>>> +		pr_warn("%s: id > 2\n", __func__);
>>>> +		return;
>>>> +	}
>>>> +	at91_ramc_base[id] = ioremap(addr, size);
>>>> +	if (!at91_ramc_base[id])
>>>> +		pr_warn("Impossible to ioremap ramc.%d 0x%x\n", id, addr);
>>>> +}
>>>
>>>
>>> If this fails then you will oops if you call either at91_ramc_read or
>>> at91_ramc_write since they don't check if at91_ramc_base[id] is a valid
>>> pointer. Either this function should panic, like the other at91_ioremap
>>> functions, or the at91_ramc_read/write functions should check for a
>>> valid pointer.
>>
>> Yes, as you pointed out, it is done in a not-related following patch.
>> I will bring the code here.
>>
>>
>>> Nitpick: The id check should probably also be BUG() or WARN() since it
>>> indicates a bug in the core AT91 code. pr_warn is likely to missed and
>>> not reported by users. Since the value is int, the check should be:
>>>
>>>   if (id < 0 || id > 1)
>>>
>>> Obviously the chance of this error happening are slim, but if you are
>>> going to check and warn for it, it should be done properly :-).
>>
>> Yes, I agree and modify it at the very moment.
> 
> 
> What do you think about that:
> If id is not setup properly, I try to find a way out by using id = 0...
> Then, a panic is added if the iremap() fails.
> 
> 
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -200,13 +200,14 @@ void __iomem *at91_ramc_base[2];
>  
>  void __init at91_ioremap_ramc(int id, u32 addr, u32 size)
>  {
> -       if (id > 1) {
> -               pr_warn("%s: id > 2\n", __func__);
> -               return;
> +       if (id < 0 || id > 1) {
> +               WARN(1, "%s: Wrong RAM controller id (%d), set it to 0\n",
> +                                                               __func__, id);
> +               id = 0;


I don't think you should try to fix the id, just issue the warning and
return. 

~Ryan
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