On Sat, Feb 1, 2020 at 10:10 AM Dimitry Andric <d...@freebsd.org> wrote: > > On 1 Feb 2020, at 18:48, Ian Lepore <i...@freebsd.org> wrote: > > > > So you're going to switch from writing 0 to writing 0xfffffffe, and > > just assume that will work the same? > > ... [Caustic sarcasm elided] > > Hmm, the data sheet says: > > Writes (0000 0001h): Cancel a command > Writes (0000 0000h): Clears field when command has been cancelled > > It seems the other bits in the register are not used for anything.
This seems pretty typical for TPM registers (in my limited experience). > So indeed it is probably better to explicitly define these values as 0x0 > and 0x1, and not use ~ or ! operators at all. I would suggest using just a plain 0 for the clear-cancel register write, unless the other bits are actually documented to have meaning, and that meaning is not W1C. My recollection is that many TPM registers only have a single real valid bit, and of those that have more than one, many are W1C. (AND4/OR4 RMW are inappropriate for W1C.) We have at least one AND4/OR4 related bugfix pending in phabricator related to this that I should go ahead and commit: https://reviews.freebsd.org/D23081 . I don't think the ~0x1 (0xff...fe) will actually do anything harmful if the other bits are ignore. But 0 is closer to the data sheet. Please un-disable the Makefile warnings removed in r357349 earlier, too. Thanks, Conrad _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
