Re: [PATCHv5 1/4] arm64: io: Use asm-generic high level MMIO accessors

On 12/6/2021 5:00 PM, Arnd Bergmann wrote:

On Mon, Dec 6, 2021 at 12:12 PM Sai Prakash Ranjan
[off-list ref] wrote:

quoted

On 12/6/2021 2:20 PM, Arnd Bergmann wrote:

quoted

I think it would be even better to flip these around and make the low-level
definitions __io_ar() and __io_bw(), and then defining the arm64 specific
macros based on those:

/* arm64-specific, don't use in portable drivers */
#define __iormb(v)     __io_ar(v)
#define __iowmb()      __io_bw()
#define __iomb()        dma_mb()

So __iormb on arm64 has some dummy control dependency stuff as well based on
("arm64: io: Ensure calls to delay routines are ordered against prior
readX()") and then we would need to change __iormb definition to __io_ar which
doesn't seem like __iormb definition to be exact right?

I'm not sure what you are asking here. As far as I can tell, __io_ar()
and __iormb() have the same calling conventions and the same barrier
requirements, so they should be interchangeable, we just need to decide
which one is the primary definition.

        Arnd

Sorry, what I meant was the literal name of these macros, i.e., __iormb() has more explicit naming as
IO read memory barrier and __io_ar() is IO after read? So doesn't it make more sense that __iormb()
should be the primary definition which is already the case and ar/bw should be based on them.

Thanks,
Sai

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