Hi Horia, On Wed, Jul 4, 2018 at 8:45 AM, Horia Geanta <horia.geanta@xxxxxxx> wrote: > I think there are two separate issues here: > > 1. Semantics of operations in io-64-nonatomic-lo-hi.h, io-64-nonatomic-hi-lo.h > > Logan, you mentioned the following (which unfortunately I somehow missed): > https://lore.kernel.org/lkml/c3f2e061-5ed1-5c74-b955-3d2bfb0da074@xxxxxxxxxxxx > The lo_hi/hi_lo functions seem to always refer to the data being written > or read not to the address operated on. > > OTOH, initial commit that added asm-generic/io-64-nonatomic-lo-hi.h and > asm-generic/io-64-nonatomic-hi-lo.h mentions: > 797a796a13df6 ("asm-generic: architecture independent readq/writeq for 32bit > environment") > - <asm-generic/io-64-nonatomic-lo-hi.h> provides non-atomic readq/ writeq with > the order of lower address -> higher address > - <asm-generic/io-64-nonatomic-hi-lo.h> provides non-atomic readq/ writeq with > reversed order > > I think we should keep the initial semantics when adding support for > io{read|write}64, i.e. "lo" and "hi" to refer to address and not to value. > > Actually this is the semantics intended for the CAAM patch, see the note at the > end of the commit message that refers to addresses, not values: > To be consistent with CAAM engine HW spec: in case of 64-bit registers, > irrespective of device endianness, the lower address should be read from > / written to first, followed by the upper address. > > > 2. CAAM driver I/O accessors for i.MX case > > CAAM block in some i.MX parts has broken endianness for 64b registers. > For e.g. for i.MX6S/SL/D/Q even though CAAM is little endian, BARs for I/O rings > have to be programmed as: > I/O Ring BAR+0: unused > I/O Ring BAR+4: IOVA (32-bit little endian) > when the proper layout (for a 64b register) would have been to program IOVA at > BAR+0. > > This explains why I/O accessors in CAAM driver handle things differently in case > caam_imx=true. > > Since this quirk cannot be accommodated in generic fashion, code dealing with > caam_imx has to stay. Should I sent a revert of patch 46e4bf08f6388 for the boot regression for now? Then the two issues you pointed out could be fixed later.
