Re: [PATCH 1/4] nvmem: sunxi_sid: Always use 32-bit MMIO reads

[Heiko Stübner]

Am Sonntag, 14. August 2022, 19:36:52 CEST schrieb Samuel Holland:
> The SID SRAM on at least some SoCs (A64 and D1) returns different values
> when read with bus cycles narrower than 32 bits. This is not immediately
> obvious, because memcpy_fromio() uses word-size accesses as long as
> enough data is being copied.
> 
> The vendor driver always uses 32-bit MMIO reads, so do the same here.
> This is faster than the register-based method, which is currently used
> as a workaround on A64. And it fixes the values returned on D1, where
> the SRAM method was being used.
> 
> The special case for the last word is needed to maintain .word_size == 1
> for sysfs ABI compatibility, as noted previously in commit de2a3eaea552
> ("nvmem: sunxi_sid: Optimize register read-out method").
> 
> Fixes: 07ae4fde9efa ("nvmem: sunxi_sid: Add support for D1 variant")
> Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx>

On a D1-Nezha:
Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>