zynq: introduce SG_FAULT to prevent access to AXI segment while PL is not ready

access to the axi segment hangs the machine when the fpga
is not programmed yet. to prevent access, we introduce a
new SG_FAULT flag, that when set on the Segment.type or
Physseg.attr, causes the fault handler to immidiately
return with an error (as if the segment would not be mapped).

during programming, we temporarily set the SG_FAULT flag
on the axi physseg, flush all processes tlb's that have
the segment mapped and when programming is done, we clear
the flag again.

1 files changed, 17 insertions, 9 deletions

diff --git a/sys/src/9/zynq/devarch.c b/sys/src/9/zynq/devarch.c
index c5c4ea0b9..ccd513b26 100644
--- a/sys/src/9/zynq/devarch.c
+++ b/sys/src/9/zynq/devarch.c
@@ -25,14 +25,15 @@ static Dirtab archdir[Qmax] = {
 };
 static int narchdir = Qbase;
 
-int temp = -128;
-ulong *devc;
-int dmadone;
+static int temp = -128;
+static ulong *devc;
+static int dmadone;
 enum { PLBUFSIZ = 8192 };
-uchar *plbuf;
-Rendez plinitr, pldoner, pldmar;
-QLock plrlock, plwlock;
-Ref plwopen;
+static uchar *plbuf;
+static Rendez plinitr, pldoner, pldmar;
+static QLock plrlock, plwlock;
+static Ref plwopen;
+static Physseg *axi;
 
 enum {
 	DEVCTRL = 0,
@@ -164,6 +165,8 @@ plirq(Ureg *, void *)
 		slcr[0x900/4] = 0xf;
 		slcr[0x240/4] = 0;
 		devc[DEVMASK] |= DONE;
+		if(axi != nil)
+			axi->attr &= ~SG_FAULT;
 		wakeup(&pldoner);
 	}
 	if((fl & DMADONE) != 0){
@@ -187,16 +190,21 @@ plinit(void)
 	slcr[FPGA0_CLK_CTRL] = 1<<20 | 10<<8;
 
 	memset(&seg, 0, sizeof seg);
-	seg.attr = SG_PHYSICAL;
+	seg.attr = SG_PHYSICAL | SG_FAULT;
 	seg.name = "axi";
 	seg.pa = 0x40000000;
 	seg.size = 0x8000000;
-	addphysseg(&seg);
+	axi = addphysseg(&seg);
 }
 
 static void
 plconf(void)
 {
+	if(axi != nil){
+		axi->attr |= SG_FAULT;
+		procflushpseg(axi);
+	}
+
 	slcr[0x240/4] = 0xf;
 	slcr[0x900/4] = 0xa;
 	devc[DEVISTS] = DONE|INITPE|DMADONE;