Re: [PATCH 4/6] scsi: ufs: exynos: Enable PRDT pre-fetching with UFSHCD_CAP_CRYPTO

[Eric Biggers]

On Wed, Feb 26, 2025 at 10:04:12PM +0000, Peter Griffin wrote:
> PRDT_PREFETCH_ENABLE[31] bit should be set when desctype field of
> fmpsecurity0 register is type2 (double file encryption) or type3
> (file and disk excryption). Setting this bit enables PRDT
> pre-fetching on both TXPRDT and RXPRDT.
> 
> Signed-off-by: Peter Griffin <peter.griffin@xxxxxxxxxx>

I assume you mean that desctype 3 provides "support for file and disk
encryption"?  The driver does use desctype 3, but it only uses the "file
encryption".  So this confused me a bit.  (BTW, in FMP terminology, "file
encryption" seems to mean "use the key provided in the I/O request", and "disk
encryption" seems to mean "use some key the firmware provided somehow".  They
can be cascaded, and the intended use cases are clearly file and disk encryption
respectively, but they don't necessarily have to be used that way.)

- Eric