Comment #135 for bugzilla 237666 : a USB3-handling problem with a investigatory fix for a cortex-a72 context

[Mark Millard]

On 2020-Sep-19, at 13:54, Mark Millard <marklmi at yahoo.com> wrote:

. . .
> 
> As stands, in my head -r363590 based context, the patch set for this
> overall currently looks like (up to E-mail variability in spaces):
> 
> # svnlite diff /usr/src/sys/dev/usb/usb_busdma.c /usr/src/sys/dev/usb/controller/xhci.c
> Index: /usr/src/sys/dev/usb/usb_busdma.c
> ===================================================================
> --- /usr/src/sys/dev/usb/usb_busdma.c	(revision 363590)
> +++ /usr/src/sys/dev/usb/usb_busdma.c	(working copy)
> @@ -737,6 +737,9 @@
> 	 */
> 	bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_POSTREAD);
> 	bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_PREREAD);
> +#ifdef __aarch64__
> +__asm __volatile("dsb ld" : : : "memory");
> +#endif
> }
> 
> /*------------------------------------------------------------------------*
> @@ -750,6 +753,9 @@
> 		return;
> 	}
> 	bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_PREWRITE);
> +#ifdef __aarch64__
> +__asm __volatile("dsb st" : : : "memory");
> +#endif
> }
> 

Looking at the lower level code it looked like DSB SY is used for
the above two automatically and it should be a valid sustitute
for DSB ST and DSB LD, even if overkill. So I'm testing with
dev/usb/usb_busdma.c reverted. (See later below.)

> /*------------------------------------------------------------------------*
> Index: /usr/src/sys/dev/usb/controller/xhci.c
> ===================================================================
> --- /usr/src/sys/dev/usb/controller/xhci.c	(revision 363590)
> +++ /usr/src/sys/dev/usb/controller/xhci.c	(working copy)
> @@ -431,6 +431,7 @@
> 
> 	phwr->hwr_ring_seg[0].qwEvrsTablePtr = htole64(addr);
> 	phwr->hwr_ring_seg[0].dwEvrsTableSize = htole32(XHCI_MAX_EVENTS);
> +	usb_bus_mem_flush_all(&sc->sc_bus, &xhci_iterate_hw_softc);
> 
> 	DPRINTF("ERDP(0)=0x%016llx\n", (unsigned long long)addr);
> 
> 

The test booted just fine, no "Resetting controller" notices or the
like. So now I have just:

# svnlite diff /usr/src/sys/dev/usb/controller/xhci.c
Index: /usr/src/sys/dev/usb/controller/xhci.c
===================================================================
--- /usr/src/sys/dev/usb/controller/xhci.c	(revision 363590)
+++ /usr/src/sys/dev/usb/controller/xhci.c	(working copy)
@@ -431,6 +431,7 @@
 
 	phwr->hwr_ring_seg[0].qwEvrsTablePtr = htole64(addr);
 	phwr->hwr_ring_seg[0].dwEvrsTableSize = htole32(XHCI_MAX_EVENTS);
+	usb_bus_mem_flush_all(&sc->sc_bus, &xhci_iterate_hw_softc);
 
 	DPRINTF("ERDP(0)=0x%016llx\n", (unsigned long long)addr);
 

for the issue. (So my earlier powerpc* SYNC comments are likely junk.)

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)