Re: [PATCH] stm32vldiscovery: allow overriding of RAM size

[Alexandre IOOSS]

On 4/3/23 16:48, Lucas C. Villa Real wrote:
> On Mon, Apr 3, 2023 at 10:54 AM Peter Maydell <peter.maydell@linaro.org 
> <mailto:peter.maydell@linaro.org>> wrote:
>
>     On Mon, 3 Apr 2023 at 13:51, Lucas Villa Real <lucasvr@gmail.com
>     <mailto:lucasvr@gmail.com>> wrote:
>      >
>      > stm32vldiscovery comes with 8KB of SRAM, which may be too low when
>      > running some workloads on QEMU. The command line argument "-m
>     mem_size"
>      > is not recognized by the current implementation, though, so one
>     cannot
>      > easily override the default memory size.
>      >
>      > This patch fixes that by adding a memory subregion according to the
>      > value provided on that command line argument. If absent, the default
>      > value of 8KB still applies.
>      >
>      > Signed-off-by: Lucas Villa Real <lucas@osdyne.com
>     <mailto:lucas@osdyne.com>>
>
>     Does the real hardware have (options for) more than 8K of SRAM here ?
>
>     thanks
>     -- PMM
>
>
> Yes, it's possible to add more (p)SRAM via the STM32F10xxx's FSMC 
> (flexible static memory controller). The new memory is mapped to FSMC 
> bank 1 at 0x6000_0000, though (as opposed to the embedded SRAM's fixed 
> address at 0x2000_0000), as I have now realized. I'm happy to send an 
> updated patch so that "-m mem_size" creates a memory subregion at 
> 0x6000_0000 instead.
>
> Best regards,
> Lucas

Looking at the STM32F100xx reference manual page 494 
(https://www.st.com/resource/en/reference_manual/rm0041-stm32f100xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf), 
FSMC is only present on high-density value line devices only. This is 
not the case of the STM32VLDISCOVERY which uses a STM32F100RB 
(low/medium-density value line).

Correct me if I'm wrong, but I believe you cannot buy a STM32VLDISCOVERY 
that could support FSMC or have more than 8KB of on-chip SRAM.

However, could it be a good idea to implement a generic STM32F100xx 
machine in QEMU that is "high-density" by default and that could be 
configured using command line options ? This could cover a wide range of 
cases with a single machine.

Thanks,
--
Alexandre

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