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

[Dr. Philipp Tomsich]

> 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;
>> };
>> 
>> struct ram_ops {
>> --
>> 2.1.4
>> 
> 
> Regards,
> Simon