Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted

[Linus Walleij]

On Tue, Mar 9, 2021 at 1:41 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:

> - A driver writer may want to choose between posted and
>   nonposted mmio based on performance considerations:
>   if writes are never serialized, posted writes should always
>   be faster. However, if the driver uses a spinlock to serialize
>   writes, then a nonposted write is likely faster than a posted
>   write followed by a read that serializes the spin_unlock.
>   In this case we want the driver to explicitly pick one over
>   the other, and not have rely on bus specific magic.

OK then I am all for having drivers explicitly choose access
method. Openness to speed optimization is a well established
Linux kernel design principle.

Yours,
Linus Walleij