[PATCH] Basic lwIP for STM32H7 BSP

[Robin Müller]

The following link contains more theoretical information about why these
sections were placed at these addresses:
https://community.st.com/s/article/FAQ-DMA-is-not-working-on-STM32H7-devices

Kind Regards
Robin

On Wed, 3 Feb 2021 at 14:44, Robin Müller <robin.mueller.m at gmail.com> wrote:

> The DMA descriptors need to be placed at the start of the SRAM3 and need
> to be aligned in a certain way. The RX buffer will take up the first
> (slightly less than) 16 kB of SRAM3 but needs to be placed
> behind the DMA descriptors. It also needs to be placed in a way that the
> MPU configuration required for the DMA descriptors will not do something
> with the RX buffers.
> In the example provided by STM32, the first 256 bytes are configured by
> MPU Config.
>
> Kind Regards
> Robin
>
>
>
> On Wed, 3 Feb 2021 at 13:43, Sebastian Huber <
> sebastian.huber at embedded-brains.de> wrote:
>
>> On 02/02/2021 20:10, Robin Mueller wrote:
>>
>> > +     /* Not an ideal solution but required for lwIP on the STM32H7 BSP.
>> > +     This places the DMA descriptors for lwIP at the start of SRAM3.
>> > +     The MPU still needs to be configured for the DMA descriptor
>> regions to be
>> > +     bufferable, non-cacheable, non-shareable (first 256 bytes) */
>> > +     .lwip_sec_stm32h7 (NOLOAD) : ALIGN_WITH_INPUT {
>> > +             . = ABSOLUTE(0x30040000);
>> > +             *(.RxDecripSection)
>> > +             . = ABSOLUTE(0x30040060);
>> > +             *(.TxDecripSection)
>> > +             . = ABSOLUTE(0x30040200);
>> > +             *(.RxArraySection)
>> > +     } >SRAM_3 AT> REGION_TEXT_LOAD
>> > +
>>
>> This is the wrong linker command file. This stuff should be in
>>
>> spec/build/bsps/arm/stm32h7/linkcmdsmemory.yml
>>
>> with an output section name like ".stm32h7_sram_3" and corresponding
>> input section names. Why do you need absolute addresses here?
>>
>> --
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