Module Name: src
Committed By: riastradh
Date: Thu Mar 10 00:14:34 UTC 2022
Modified Files:
src/sys/dev/pci: gffb.c
Log Message:
gffb(4): Nix membar_sync and explain what's going on here.
To generate a diff of this commit:
cvs rdiff -u -r1.18 -r1.19 src/sys/dev/pci/gffb.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/pci/gffb.c
diff -u src/sys/dev/pci/gffb.c:1.18 src/sys/dev/pci/gffb.c:1.19
--- src/sys/dev/pci/gffb.c:1.18 Thu Mar 10 00:14:25 2022
+++ src/sys/dev/pci/gffb.c Thu Mar 10 00:14:33 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: gffb.c,v 1.18 2022/03/10 00:14:25 riastradh Exp $ */
+/* $NetBSD: gffb.c,v 1.19 2022/03/10 00:14:33 riastradh Exp $ */
/*
* Copyright (c) 2013 Michael Lorenz
@@ -35,7 +35,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: gffb.c,v 1.18 2022/03/10 00:14:25 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: gffb.c,v 1.19 2022/03/10 00:14:33 riastradh Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -1133,12 +1133,23 @@ gffb_putchar(void *cookie, int row, int
if (rv == GC_OK)
return;
+ /*
+ * Use gffb_sync to wait for the engine to become idle before
+ * we start scribbling into VRAM -- we woudn't want to stomp on
+ * a scroll in progress or a prior glyphcache_add that hasn't
+ * completed yet on the GPU.
+ */
mutex_enter(&sc->sc_lock);
gffb_sync(sc);
sc->sc_putchar(cookie, row, col, c, attr);
- membar_sync();
mutex_exit(&sc->sc_lock);
+ /*
+ * If glyphcache_try asked us to, cache the newly written
+ * character. This will issue a gffb_bitblt which will wait
+ * for our CPU writes to the framebuffer in VRAM to complete
+ * before triggering GPU reads from the framebuffer in VRAM.
+ */
if (rv == GC_ADD) {
glyphcache_add(&sc->sc_gc, c, x, y);
}
