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.
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(-)
Index: linux-stable/arch/alpha/include/asm/io.h
===================================================================
--- linux-stable.orig/arch/alpha/include/asm/io.h 2020-05-06 08:23:47.000000000 +0200
+++ linux-stable/arch/alpha/include/asm/io.h 2020-05-06 18:33:47.000000000 +0200
@@ -6,6 +6,7 @@
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/delay.h>
#include <asm/compiler.h>
#include <asm/pgtable.h>
#include <asm/machvec.h>
@@ -481,9 +482,9 @@ extern inline void writeq(u64 b, volatil
#define iowrite16be(v,p) iowrite16(cpu_to_be16(v), (p))
#define iowrite32be(v,p) iowrite32(cpu_to_be32(v), (p))
-#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
