[U-Boot] [PATCH 1/9] dm: allow 4GB of DRAM on 32bit systems

[Alexander Graf]

On 02.08.18 23:31, Dr. Philipp Tomsich wrote:
> 
>> On 2 Aug 2018, at 22:36, Simon Glass <sjg at chromium.org> wrote:
>>
>> On 26 July 2018 at 07:59, Philipp Tomsich
>> <philipp.tomsich at theobroma-systems.com <mailto:philipp.tomsich at theobroma-systems.com>> wrote:
>>> Even on 32bit systems a full 4GB of DRAM may be installed and reported
>>> by the DRAM controller.  Whether these 4GB are larger available
>>> depends on the size/configuration of address decoding windows and
>>> architectural features (e.g. consider a hypothetical architecture that
>>> uses dedicated instructions to access the 'memory-mapped' peripheral
>>> IO ranges).  In U-Boot, the available DRAM, as reported by the
>>> device-model is independent of the accessible DRAM (i.e. adjusted top
>>> and effective size).
>>>
>>> This was first reported against the RK3288, which may have 4GB DRAM
>>> attached, but will have a small (e.g. 128MB) window not accessible due
>>> to address decoding limitations.
>>>
>>> The solution is to increase the types used for storing the ram_size to
>>> have at least 33 bits even on 32bit systems... i.e. we need to use a
>>> u64 for these always (this was previously only the case for
>>> PHYS_64BIT, which will have unwanted side-effects for 32bit systems
>>> and would require more intrusive changes).
>>>
>>> This commit changes the size-field in 'struct ram' and the ram_size in
>>> 'gd' to be a u64.
>>>
>>> Reported-by: Marty E. Plummer <hanetzer at startmail.com>
>>> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
>>> ---
>>>
>>> include/asm-generic/global_data.h | 2 +-
>>> include/ram.h                     | 9 ++++++++-
>>> 2 files changed, 9 insertions(+), 2 deletions(-)
>>>
>>
>> Reviewed-by: Simon Glass <sjg at chromium.org <mailto:sjg at chromium.org>>
>>
>>> diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
>>> index 0fd4900..f3d687c 100644
>>> --- a/include/asm-generic/global_data.h
>>> +++ b/include/asm-generic/global_data.h
>>> @@ -55,7 +55,7 @@ typedef struct global_data {
>>>        unsigned long ram_base;         /* Base address of RAM used by U-Boot */
>>>        unsigned long ram_top;          /* Top address of RAM used by U-Boot */
>>>        unsigned long relocaddr;        /* Start address of U-Boot in RAM */
>>> -       phys_size_t ram_size;           /* RAM size */
>>> +       u64 ram_size;                   /* RAM size */
>>>        unsigned long mon_len;          /* monitor len */
>>>        unsigned long irq_sp;           /* irq stack pointer */
>>>        unsigned long start_addr_sp;    /* start_addr_stackpointer */
>>> diff --git a/include/ram.h b/include/ram.h
>>> index 67e22d7..1fe024f 100644
>>> --- a/include/ram.h
>>> +++ b/include/ram.h
>>> @@ -9,7 +9,14 @@
>>>
>>> struct ram_info {
>>>        phys_addr_t base;
>>> -       size_t size;
>>> +       /*
>>> +        * We use a 64bit type for the size to correctly handle 32bit
>>> +        * systems with 4GB of DRAM (which would overflow a 32bit type
>>> +        * and read back as 0).  For 64bit systems, we assume (for now)
>>
>> forever :-)
>>
>>> +        * that they will always have less than 2^65 byte of DRAM
>>> +        * installed. -- prt
>>
>> Is the prt your signature? I suggest dropping it.
> 
> In fact it is. But I’ll need to rewrite the entire comment anyway for the next
> version of this series as there’s even more functions and places that the
> memory size is stored in...
> 
>>
>>> +        */
>>> +       u64 size;

With LPAE available in all modern ARM cores, shouldn't phys_addr_t just
be u64? And then we'd probably want to use that throughout the code, right?


Alex