Messages in this thread | | | Date | Thu, 22 Sep 2022 13:00:28 +0200 | From | Miquel Raynal <> | Subject | Re: [mtd:nand/next 11/31] drivers/mtd/nand/raw/cadence-nand-controller.c:1893:4: error: implicit declaration of function 'ioread64_rep' is invalid in C99 |
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Hi Arnd,
arnd@arndb.de wrote on Thu, 22 Sep 2022 12:52:36 +0200:
> On Thu, Sep 22, 2022, at 11:36 AM, Miquel Raynal wrote: > > vkorenblit@sequans.com wrote on Thu, 22 Sep 2022 10:18:46 +0200: > >> > >> Correct, this was my initial idea. However, this driver should work > >> with every architecture or do we limit the scope to arm/arm64/x86_64? > > > > The driver should work on ARM and aarch64, I'm not aware of other > > architectures with this IP. > > > > The driver should compile when COMPILE_TEST=y. > > It should also be written in a way that makes it plausible to > use elsewhere. Since this is just a licensed IP core, there is > a good chance that someone reused it on mips or riscv, or > anything else.
Fair enough.
> >> >> I believe what Valentin wanted to achieve in the first place, was to > >> >> use 64-bit accesses when relevant (otherwise it does not work). > >> > The width is read from a device specific register at > >> > runtime, it is not related to the architecture you are > >> > running on, presumably this is hardwired during the > >> > design of an SoC, based on the capabilities of the DMA > >> > engine: > > > > Well, yes, but in the mean time 64-bit DMA width will never be > > used on 32-bit platforms. > > Why? Most architectures (including x86 and arm) allow you to > run a 32-bit kernel on a 64-bit SoC. While this is almost always > a bad idea to actually do, a driver should be written to > work correctly in this setup.
Oh right, I forgot about that.
> >> > This usually means the largest access that is valid for > >> > reading from the FIFO, but usually smaller accesses work > >> > as well, just slower. > > > > Mmh, ok, that's interesting, thanks for the pointer. > > > > But in the mean time I am only half satisfied, because we plan to do > > twice more accesses than needed _just_ because of a the COMPILE_TEST > > constraint. > > In my example, I had an #ifdef so it would only fall back > to 32-bit accesses on the 64-bit register when running an > actual 32-bit kernel, but leaving the 64-bit case efficient.
All right, thanks for all your valuable feedback Arnd!
Cheers, Miquèl
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