[src/trunk]: src/sys/dev/pci add a comment on PCI_MAGIC_IO_RANGE

[macallan <macallan%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b285eaf8015f
branches:  trunk
changeset: 752426:b285eaf8015f
user:      macallan <macallan%NetBSD.org@localhost>
date:      Thu Feb 25 21:09:00 2010 +0000

description:
add a comment on PCI_MAGIC_IO_RANGE

diffstat:

 sys/dev/pci/genfb_pci.c |  33 +++++++++++++++++++++++++++++----
 1 files changed, 29 insertions(+), 4 deletions(-)

diffs (78 lines):

diff -r ba3ce07274c3 -r b285eaf8015f sys/dev/pci/genfb_pci.c
--- a/sys/dev/pci/genfb_pci.c   Thu Feb 25 20:56:20 2010 +0000
+++ b/sys/dev/pci/genfb_pci.c   Thu Feb 25 21:09:00 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: genfb_pci.c,v 1.23 2009/08/24 11:32:49 jmcneill Exp $ */
+/*     $NetBSD: genfb_pci.c,v 1.24 2010/02/25 21:09:00 macallan Exp $ */
 
 /*-
  * Copyright (c) 2007 Michael Lorenz
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfb_pci.c,v 1.23 2009/08/24 11:32:49 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfb_pci.c,v 1.24 2010/02/25 21:09:00 macallan Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -97,6 +97,7 @@
        struct pci_genfb_softc *sc = device_private(self);
        struct pci_attach_args *pa = aux;
        struct genfb_ops ops;
+       pcireg_t rom;
        int idx, bar, type;
        char devinfo[256];
 
@@ -136,7 +137,7 @@
        /* mmap()able bus ranges */
        idx = 0;
        bar = 0x10;
-       while (bar < 0x30) {
+       while (bar < 0x34) {
 
                type = pci_mapreg_type(sc->sc_pc, sc->sc_pcitag, bar);
                if ((type == PCI_MAPREG_TYPE_MEM) || 
@@ -148,10 +149,15 @@
                            &sc->sc_ranges[idx].flags);
                        idx++;
                }
-               sc->sc_bars[(bar - 0x10) >> 2] =
+               sc->sc_bars[(bar - 0x10) >> 2] = rom =
                    pci_conf_read(sc->sc_pc, sc->sc_pcitag, bar);
+               if ((bar == PCI_MAPREG_ROM) && (rom != 0)) {
+                       pci_conf_write(sc->sc_pc, sc->sc_pcitag, bar, rom |
+                           PCI_MAPREG_ROM_ENABLE);
+               }
                bar += 4;
        }
+
        sc->sc_ranges_used = idx;                           
 
        ops.genfb_ioctl = pci_genfb_ioctl;
@@ -258,6 +264,25 @@
         * somewhere in a MD header and compile this code only if all are
         * present
         */
+       /*
+        * no.
+        * PCI_IOAREA_PADDR would be completely, utterly wrong and completely
+        * useless for the following reasons:
+        * - it's a bus address, not a physical address
+        * - there's no guarantee it's the same for each host bridge
+        * - it's already taken care of by the IO tag
+        * PCI_IOAREA_OFFSET is the same as PCI_MAGIC_IO_RANGE
+        * PCI_IOAREA_SIZE is also useless:
+        * - many cards don't decode more than 16 bit IO anyway
+        * - even machines with more than 64kB IO space try to keep everything
+        *   within 64kB for the reason above
+        * - IO ranges tend to be small so in most cases you can't cram enough
+        *   cards into a single machine to exhaust 64kB IO space
+        * - machines which need this tend to prefer memory space anyway
+        * - the only use for this right now is to allow the Xserver to map
+        *   VGA registers on macppc and a few other powerpc ports, shark uses
+        *   a similar mechanism, and what they need is always within 64kB
+        */
 #ifdef PCI_MAGIC_IO_RANGE
        /* allow to map our IO space */
        if ((offset >= PCI_MAGIC_IO_RANGE) &&