Messages in this thread | | | Date | Wed, 21 Sep 2022 18:38:07 +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 Wed, 21 Sep 2022 17:49:11 +0200:
> On Wed, Sep 21, 2022, at 4:47 PM, Miquel Raynal wrote: > > > > The (erased) context of this thread: > > https://lore.kernel.org/llvm/202209210641.MziHAbW7-lkp@intel.com/ > > > > vkorenblit@sequans.com wrote on Wed, 21 Sep 2022 14:27:47 +0200: > > > >> Hi Miquel, > >> > >> I see that x86_64 doesn't support readsq/writesq because of > >> CONFIG_GENERIC_IOMAP (I was building for arm64). However, > >> __raw_readq/writeq are available and there are a few drivers > >> using them. > > > > I would suggest to rather try using [read|write]sq() to get rid > > of the CONFIG_GENERIC_IOMAP dependency. But it looks like those > > functions are not defined on 32-bit architectures anyway. So if we want > > the driver to compile on both arm and aarch64, it will not be enough. > > > > In practice, I guess we should never have the 64-bit accessor executed > > when running on a 32-bit platform thanks to the following conditions: > > > > 1885 u8 data_dma_width = cdns_ctrl->caps2.data_dma_width; > > 1886 > > 1887 int len_in_words = (data_dma_width == 4) ? len >> 2 : len >> 3; > > 1888 > > 1889 /* read alingment data */ > > 1890 if (data_dma_width == 4) > > 1891 ioread32_rep(cdns_ctrl->io.virt, buf, len_in_words); > > 1892 else > >> 1893 ioread64_rep(cdns_ctrl->io.virt, buf, len_in_words); > > > > So maybe we could have something awful yet simple, like the following > > within the Cadence driver: > > > > #if !CONFIG_64BIT > > readsq(...) { BUG()? } > > #endif > > > > Arnd, I've seen a couple of similar issues on the mailing lists in the > > past 5 years but I could not find any working solution, I don't know > > how all these threads have settled in the end. I thought maybe you > > would have a better idea than the above hack :) > > There are a lot of different things going on here, so I need > to unwind a bit:
Thanks for all your feedback!
> - every architecture should provide readsq()/readsl()/readsw()/readsb() > these days, regardless of CONFIG_GENERIC_IOMAP. If x86 does > not have that, we should fix asm-generic/io.h.
ARM does not seem to define readsq/writesq. Should it be fixed?
> - CONFIG_GENERIC_IOMAP just means an architecture uses the generic > ioread32_rep() style wrapper around readsl()/insl(). On most > architectures (not x86), insl() is implemented as a wrapper around > readsl() itself, so readsl() and ioread32_rep() should be identical.
Ok. But if CONFIG_GENERIC_IOMAP=n (ARM, aarch64, x86_64), ioread64_rep is then only defined if CONFIG_64BIT. As it is based on readsq/writesq() and those must be defined (as you said), I don't get why the *64_rep() helpers are not defined in all cases. Maybe because no 32-bit system _should_ need them? But then compile testing gets more difficult.
> - For a FIFO, you cannot use readq() but have to use __raw_readq() > to get the correct endianness. You cannot use this for an > MMIO register with side-effects though, as this needs the byteswap > and the barrier in readsl().
I'm not sure about the true definition of "FIFO" as you say. I guess you just mean reading from a BE device?
In this case I guess we need the barrier+byteswap helpers.
> - On 32-bit architectures, there is no generic way to access a 64-bit > MMIO location as you say. However, depending on the device you are > accessing, you can replace __raw_readq() with a pair of > __raw_readl(), along the lines of > include/linux/io-64-nonatomic-{lo-hi,hi-lo}.h
Ah ok, so in the end the per-driver implementation is preferred.
> >> Do you want me to re-implement readsq and writesq in Cadence > >> driver privately or do you suggest a different (cleaner) approach? > > > > I would rather prefer to avoid this solution, as anyway I believe there > > is no "generic" implementation working in all cases, there were a > > couple of attempts IIRC to bring generic helpers like the above for all > > architectures, but none of them landed in Linus' tree, probably because > > it just cannot be made... > > If anyone has a datasheet for the cadence driver, they should be > able to look up how one can access the FIFO in 8-byte mode using > 32-bit accesses. I think it's something like
I don't think this is actually what we want. My understanding is (Valentin, please correct me if I'm wrong): - on ARM: we will always use 32-bit accesses - on aarch64: we may use either 32-bit or 64-bit accesses - on other architectures: we only want to compile test
I believe what Valentin wanted to achieve in the first place, was to use 64-bit accesses when relevant (otherwise it does not work).
> static inline void cadence_nand_readsq(const volatile void __iomem *addr, > void *buffer, unsigned int count) > { > if (count) { > u64 *buf = buffer; > > do { > #ifdef __raw_readq > u64 x = __raw_readq(addr); > *buf++ = x; > #else > u32 *buf32 = (void *)buf; > buf32[0] = __raw_readl(addr + OFF0); > buf32[1] = __raw_readl(addr + OFF1); > buf++; > #endif > } while (--count); > } > } > > Most likely, OFF0 is zero, while OFF1 is 4 here, but that > depends on how the FIFO register is implemented. > > Arnd
Thanks, Miquèl
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