Hi Ard, I'm not familiar with how dma-ranges will be utilized, could you educate me more? For example, PlatformInit may assign dma-ranges = <0 0x100000000> // 0 ~ 4GB, but we still want to prevent DMA access from some sensitive regions within this huge range. Does that mean we rely on reserved-memory node to prevent DMA from some regions? Or are there any other nodes that PlatformInit/Payload has to provide? Thanks, Chasel > -----Original Message----- > From: Simon Glass <sjg@xxxxxxxxxxxx> > Sent: Tuesday, November 21, 2023 9:38 AM > To: Ard Biesheuvel <ardb@xxxxxxxxxx> > Cc: Tan, Lean Sheng <sheng.tan@xxxxxxxxxxxxx>; Devicetree Discuss > <devicetree@xxxxxxxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Guo, Gua > <gua.guo@xxxxxxxxx>; Chiu, Chasel <chasel.chiu@xxxxxxxxx>; Dong, Guo > <guo.dong@xxxxxxxxx>; Brune, Maximilian <maximilian.brune@xxxxxxxxxxxxx> > Subject: Re: DMA not supported below 4GB > > Hi Ard, > > On Tue, 21 Nov 2023 at 10:31, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > dma-ranges is supposed to handle this, but I'm not sure how well it > interoperates with SMMUs (which remap DMA addresses into a virtual address > space, and this can both solve and create issues when it comes to DMA address > limits). > > > > Adding a 'no-dma-above-4g' property is a bad idea. Not only does it > > result in potential inconsistencies wrt 'dma-ranges', it also only > > describes 32 bits of DMA addressing capability, and other DMA > > addressing limits exist too (40 bits is also common) > > OK, thank you for that. We will use dma-ranges for this. > > Regards, > Simon > > > > > > > > > > > On Tue, 21 Nov 2023 at 12:01, Lean Sheng Tan <sheng.tan@xxxxxxxxxxxxx> > wrote: > >> > >> Added Ard for some input on this. > >> > >> Best Regards, > >> Lean Sheng Tan > >> > >> > >> > >> 9elements GmbH, Kortumstraße 19-21, 44787 Bochum, Germany > >> Email: sheng.tan@xxxxxxxxxxxxx > >> Phone: +49 234 68 94 188 > >> Mobile: +49 176 76 113842 > >> > >> Registered office: Bochum > >> Commercial register: Amtsgericht Bochum, HRB 17519 > >> Management: Sebastian German, Eray Bazaar > >> > >> Data protection information according to Art. 13 GDPR > >> > >> > >> On Tue, 14 Nov 2023 at 23:17, Simon Glass <sjg@xxxxxxxxxxxx> wrote: > >>> > >>> Hi, > >>> > >>> Some devices do not support DMA above 4GB. Is there a way to express > >>> this in the devicetree? > >>> > >>> Should we add sometimes a 'no-dma-above-4g' property? > >>> > >>> Or should we be using dma-ranges for this? > >>> > >>> Regards, > >>> Simon > >>>
