Re: [PATCH 1/1] ARM: LPAE: use phys_addr_t instead of unsigned long in outercache hooks

[Leizhen (ThunderTown)]

On 2020/12/26 20:13, Russell King - ARM Linux admin wrote:
> On Fri, Dec 25, 2020 at 07:44:58PM +0800, Zhen Lei wrote:
>> The outercache of some Hisilicon SOCs support physical addresses wider
>> than 32-bits. The unsigned long datatype is not sufficient for mapping
>> physical addresses >= 4GB. The commit ad6b9c9d78b9 ("ARM: 6671/1: LPAE:
>> use phys_addr_t instead of unsigned long in outercache functions") has
>> already modified the outercache functions. But the parameters of the
>> outercache hooks are not changed. This patch use phys_addr_t instead of
>> unsigned long in outercache hooks: inv_range, clean_range, flush_range.
>>
>> To ensure the outercache that does not support LPAE works properly, do
>> cast phys_addr_t to unsigned long by adding a middle-tier function.
> 
> Please don't do that. The cast can be done inside the L2 functions
> themselves without needing all these additional functions.

OK. At first, I wanted to fit in like this:

-static void l2c220_inv_range(unsigned long start, unsigned long end)
+static void l2c220_inv_range(phys_addr_t lpae_start, phys_addr_t lpae_end)
 {
+  unsigned long start = lpae_start;
+  unsigned long end = lpae_end;


> 
> We probably ought to also add some protection against addresses > 4GB,
> although these are hot paths, so we don't want to add tests in these
> functions. Maybe instead checking whether the system has memory above
> 4GB while the L2 cache is being initialised would be a good idea?
> 

I'm sorry, I didn't quite understand what you meant. Currently, the
biggest problem is the compilation problem. The sizeof(long) may be
32, and the 64-bit physical address cannot be transferred from outcache
functions to outcache hooks.