[PATCH] Basic lwIP for STM32H7 BSP

[Robin Müller]

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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