Re: [PATCH v5 13/15] MIPS: JZ4770: Workaround for corrupted DMA transfers

[Paul Cercueil]

Hi,
Hi,

> > [...]
> >
> >  +/*
> >  + * We have seen MMC DMA transfers read corrupted data from SDRAM 
> > when a burst
> >  + * interval ends at physical address 0x10000000. To avoid this 
> > problem, we
> >  + * remove the final page of low memory from the memory map.
> >  + */
> >  +void __init jz4770_reserve_unsafe_for_dma(void)
> >  +{
> >  +       int i;
> >  +
> >  +       for (i = 0; i < boot_mem_map.nr_map; i++) {
> >  +               struct boot_mem_map_entry *entry = boot_mem_map.map 
> > + i;
> >  +
> >  +               if (entry->type != BOOT_MEM_RAM)
> >  +                       continue;
> >  +
> >  +               if (entry->addr + entry->size != 0x10000000)
> >  +                       continue;
> >  +
> >  +               entry->size -= PAGE_SIZE;
> >  +               break;
> >  +       }
> >  +}
> >  +
>
> Just a wild idea (probably bad too). Changing the memory node in the
> device tree to skip this physical address would work I think. What is
> your opinion about that?

I guess it would work as well, but I don't think this fix should be in 
devicetree.

-Paul