On Thu, May 07, 2020 at 04:06:31AM -0400, Mikulas Patocka wrote: > > > On Wed, 6 May 2020, Mikulas Patocka wrote: > > > > > > > On Wed, 6 May 2020, Arnd Bergmann wrote: > > > > > On Wed, May 6, 2020 at 1:21 PM Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > > /* > > > > * The yet supported machines all access the RTC index register via > > > > * an ISA port access but the way to access the date register differs ... > > > > + * > > > > + * The ISA bus on Alpha Avanti doesn't like back-to-back accesses, > > > > + * we need to add a small delay. > > > > */ > > > > #define CMOS_READ(addr) ({ \ > > > > outb_p((addr),RTC_PORT(0)); \ > > > > +udelay(2); \ > > > > inb_p(RTC_PORT(1)); \ > > > > > > > > > The inb_p() / outb_p() functions are meant to already have a delay in them, > > > maybe we should just add it there for alpha? > > > > > > Arnd > > > > Yes, that is possible too - it fixes the real time clock hang for me. > > > > > > -#define inb_p inb > > -#define inw_p inw > > -#define inl_p inl > > +#define inb_p(x) (ndelay(300), inb(x)) > > +#define inw_p(x) (ndelay(300), inw(x)) > > +#define inl_p(x) (ndelay(300), inl(x)) > > #define outb_p outb > > #define outw_p outw > > #define outl_p outl > > 300ns was too low. We need at least 1400ns to fix the hang reliably. > > Mikulas > > > From: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > The patch 92d7223a74235054f2aa7227d207d9c57f84dca0 ("alpha: io: reorder > barriers to guarantee writeX() and iowriteX() ordering #2") broke boot on > the Alpha Avanti platform. > > The patch changes timing between accesses to the ISA bus, in particular, > it reduces the time between "write" access and a subsequent "read" access. > > This causes lock-up when accessing the real time clock and serial ports. > > This patch fixes the real time clock by adding a small delay to the inb_p, > inw_p and inl_p macros. > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Fixes: 92d7223a7423 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2") > Cc: stable@xxxxxxxxxxxxxxx # v4.17+ > > --- > arch/alpha/include/asm/io.h | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) <snip> This is not in a format that anyone can apply it in, please resend in a proper way if you wish for it to be accepted. thanks, greg k-h