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

[Simon Glass]

Hi,

On 3 September 2018 at 16:29, Lokesh Vutla <lokeshvutla at ti.com> wrote:
>
>
> On Sunday 02 September 2018 11:19 PM, Alexander Graf wrote:
>>
>>
>>> Am 02.09.2018 um 18:04 schrieb Vagrant Cascadian <vagrant at debian.org>:
>>>
>>>> On 2018-09-02, Alexander Graf <agraf at suse.de> wrote:
>>>>> 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?
>>>
>>> Quite a few currently supported boards do not support LPAE, e.g. imx6.
>>
>> What I'm trying to say is that we probably want to make phys_addr_t be u64 when CONFIG_LPAE is set.
>
> That's right. Enabling PHYS_64BIT should be sufficient. Based on this
> phys_addr_t should be set to u32 or u64. arm already does that[1].
>
> [1]
> http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/include/asm/types.h;h=9af7353f0866f05dbe298a603d52d90e9c8e6d28;hb=HEAD
>

Yes I agree. So will this patch be changed?

Regards,
Simon