<div dir="ltr"><div><div>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 <br></div>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.<br>In the example provided by STM32, the first 256 bytes are configured by MPU Config.<br><br></div><div>Kind Regards<br></div><div>Robin<br></div><div><br></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 3 Feb 2021 at 13:43, Sebastian Huber <<a href="mailto:sebastian.huber@embedded-brains.de">sebastian.huber@embedded-brains.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 02/02/2021 20:10, Robin Mueller wrote:<br>
<br>
> + /* Not an ideal solution but required for lwIP on the STM32H7 BSP.<br>
> + This places the DMA descriptors for lwIP at the start of SRAM3.<br>
> + The MPU still needs to be configured for the DMA descriptor regions to be<br>
> + bufferable, non-cacheable, non-shareable (first 256 bytes) */<br>
> + .lwip_sec_stm32h7 (NOLOAD) : ALIGN_WITH_INPUT {<br>
> + . = ABSOLUTE(0x30040000);<br>
> + *(.RxDecripSection)<br>
> + . = ABSOLUTE(0x30040060);<br>
> + *(.TxDecripSection)<br>
> + . = ABSOLUTE(0x30040200);<br>
> + *(.RxArraySection)<br>
> + } >SRAM_3 AT> REGION_TEXT_LOAD<br>
> +<br>
<br>
This is the wrong linker command file. This stuff should be in<br>
<br>
spec/build/bsps/arm/stm32h7/linkcmdsmemory.yml<br>
<br>
with an output section name like ".stm32h7_sram_3" and corresponding <br>
input section names. Why do you need absolute addresses here?<br>
<br>
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</blockquote></div>