On Thu, Sep 8, 2022 at 3:04 PM <Conor.Dooley@xxxxxxxxxxxxx> wrote: > > On 08/09/2022 14:01, Biju Das wrote: > > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > > > Hi Conor, > > > > Thanks for the feedback. > > > >> Subject: Re: [RFC PATCH 1/2] riscv: vendors: andes: Add support to > >> configure the PMA regions > >> > >> On 08/09/2022 09:39, Biju Das wrote: > >>> EXTERNAL EMAIL: Do not click links or open attachments unless you know > >>> the content is safe > >>> > >>> Hi Conor, Atish, > >>> > >>> What RISC-V devices you have? > >> > >> A bunch ;) > >> > >> A __couple__ PolarFire SoC boards, HiFive Unleashed, D1 Nezha, Canaan > >> k210 MAIX something & the VisionFive. > > > > If standard DMA api works without any issue means, on these platforms > > IO Coherence port is enabled in the hardware. So all peripherals > > involving DMA work as expected. > > > >>> Ours is RISC-V uniprocessor without IO Coherence Port. > >> > >> What does "IO Coherence Port" mean? Zicbo*? > > > > The HW will provide coherency between CPU and peripheral. > > > > If Zibco* is uniprocessor, then highly it may not have IO coherence > > Port enabled in their design. > > Zicbo* are cache management extensions as Geert pointed out. > > > > > Guo, Please confirm. > > > >> > >>> Currently USB, ethernet, SDHI/eMMC doesn't work with standard DMA > >>> api's. > >> > >> Sounds pretty similar to the D1 so. > >> > >>> On RISC-V world, how do we handle DMA api for uniprocessor without IO > >>> Coherence Port? > >> > >> If you do mean Zicbo* you're into errata territory there & I don't know > >> if that'll be acceptable upstream - not for me to make that call... > > > > It is not errata for sure. It is a HW design where we don't have > > IO cache coherency port enabled in the HW. So looks like it is not > > an extension or errata but it is core stuff. > > If you do non-coherent stuff that is not Zicbo*, the precedence set by > the D1 is errata. As I said to Prabhakar earlier, do a > `git grep "ERRATA_THEAD*`. I am not a maintainer so I don't know the > "rules" about doing cache management without the dedicated extensions > are. > Maybe we could have a discussion about this topic at LPC too ;) Cheers, Prabhakar
