[src/trunk]: src/sys/arch/arm/arm32 A few bus_dmatag_subregion fixes

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

details:   https://anonhg.NetBSD.org/src/rev/a15d1b7af98f
branches:  trunk
changeset: 938436:a15d1b7af98f
user:      skrll <skrll%NetBSD.org@localhost>
date:      Tue Sep 08 10:30:17 2020 +0000

description:
A few bus_dmatag_subregion fixes

- return EOPNOTSUPP if min_addr isn't less than max_addr
- fix the subset check to ensure that all the ranges in the parent tag are
  within the {min,max}_addr range.  If so we can just continue to use the
  parent tag.
- when building the new ranges read the parent tag range rather than un-
  initialised memory.
- remove the max_addr != 0xffffffff check - the overflow should be handled
  by the unsigned arithmetic for arm32.
- add a KASSERT
- add comments

diffstat:

 sys/arch/arm/arm32/bus_dma.c |  41 +++++++++++++++++++++++++++++++----------
 1 files changed, 31 insertions(+), 10 deletions(-)

diffs (87 lines):

diff -r afbecbb3d20c -r a15d1b7af98f sys/arch/arm/arm32/bus_dma.c
--- a/sys/arch/arm/arm32/bus_dma.c      Tue Sep 08 10:07:35 2020 +0000
+++ b/sys/arch/arm/arm32/bus_dma.c      Tue Sep 08 10:30:17 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bus_dma.c,v 1.122 2020/06/20 07:10:36 skrll Exp $      */
+/*     $NetBSD: bus_dma.c,v 1.123 2020/09/08 10:30:17 skrll Exp $      */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 2020 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
 #include "opt_cputypes.h"
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.122 2020/06/20 07:10:36 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.123 2020/09/08 10:30:17 skrll Exp $");
 
 #include <sys/param.h>
 
@@ -1811,6 +1811,8 @@
 _bus_dmatag_subregion(bus_dma_tag_t tag, bus_addr_t min_addr,
     bus_addr_t max_addr, bus_dma_tag_t *newtag, int flags)
 {
+       if (min_addr >= max_addr)
+               return EOPNOTSUPP;
 
 #ifdef _ARM32_NEED_BUS_DMA_BOUNCE
        struct arm32_dma_range *dr;
@@ -1818,9 +1820,15 @@
        size_t nranges = 0;
        size_t i;
        for (i = 0, dr = tag->_ranges; i < tag->_nranges; i++, dr++) {
-               if (dr->dr_sysbase <= min_addr
-                   && max_addr <= dr->dr_sysbase + dr->dr_len - 1) {
+               /*
+                * Are all the ranges in the parent tag a subset of the new
+                * range? If yes, we can continue to use the parent tag.
+                */
+               if (dr->dr_sysbase >= min_addr
+                   && dr->dr_sysbase + dr->dr_len - 1 <= max_addr) {
                        subset = true;
+               } else {
+                       subset = false;
                }
                if (min_addr <= dr->dr_sysbase + dr->dr_len
                    && max_addr >= dr->dr_sysbase) {
@@ -1854,22 +1862,35 @@
                dr->dr_busbase = min_addr;
                dr->dr_len = max_addr + 1 - min_addr;
        } else {
-               for (i = 0; i < nranges; i++) {
-                       if (min_addr > dr->dr_sysbase + dr->dr_len
-                           || max_addr < dr->dr_sysbase)
+               struct arm32_dma_range *pdr;
+
+               for (i = 0, pdr = tag->_ranges; i < tag->_nranges; i++, pdr++) {
+                       KASSERT(nranges != 0);
+
+                       if (min_addr > pdr->dr_sysbase + pdr->dr_len
+                           || max_addr < pdr->dr_sysbase) {
+                               /*
+                                * this range doesn't overlap with new limits,
+                                * so skip.
+                                */
                                continue;
-                       dr[0] = tag->_ranges[i];
+                       }
+                       /*
+                        * Copy the range and adjust to fit within the new
+                        * limits
+                        */
+                       dr[0] = pdr[0];
                        if (dr->dr_sysbase < min_addr) {
                                psize_t diff = min_addr - dr->dr_sysbase;
                                dr->dr_busbase += diff;
                                dr->dr_len -= diff;
                                dr->dr_sysbase += diff;
                        }
-                       if (max_addr != 0xffffffff
-                           && max_addr + 1 < dr->dr_sysbase + dr->dr_len) {
+                       if (max_addr <= dr->dr_sysbase + dr->dr_len - 1) {
                                dr->dr_len = max_addr + 1 - dr->dr_sysbase;
                        }
                        dr++;
+                       nranges--;
                }
        }