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diff --git a/sys/powerpc/powerpc/busdma_bounce.c b/sys/powerpc/powerpc/busdma_bounce.c
--- a/sys/powerpc/powerpc/busdma_bounce.c
+++ b/sys/powerpc/powerpc/busdma_bounce.c
@@ -115,17 +115,34 @@
#include "../../kern/subr_busdma_bounce.c"
/*
- * Returns true if the address falls within the tag's exclusion window, or
- * fails to meet its alignment requirements.
+ * Returns true if this page needs bouncing.
+ *
+ * A page needs bouncing if either:
+ * (1) its physical address is outside the tag's allowed range, or
+ * (2) it starts a new segment (i.e., paddr is not the direct continuation
+ * of the previous segment's end) and doesn't satisfy the tag's
+ * alignment constraint on that new segment's start.
+ *
+ * `seg_end` is the expected physical address of the byte immediately after
+ * the previous segment (i.e., prev_curaddr + prev_sgsize as passed to
+ * _bus_dmamap_addseg). Callers walking a buffer page-by-page should pass
+ * ~(bus_addr_t)0 for the first page (no previous segment) and update
+ * seg_end after each iteration from the actual curaddr they added to the
+ * segment list (source paddr if not bounced, bounce paddr if bounced).
+ * A page whose paddr matches seg_end continues the previous segment via
+ * addseg's coalescer and inherits alignment from the segment head; only
+ * physically-discontiguous pages start new segments requiring alignment
+ * re-check.
*/
static __inline bool
-must_bounce(bus_dma_tag_t dmat, bus_addr_t paddr)
+must_bounce(bus_dma_tag_t dmat, bus_addr_t paddr, bus_addr_t seg_end)
{
if (dmat->iommu == NULL && paddr > dmat->common.lowaddr &&
paddr <= dmat->common.highaddr)
return (true);
- if (!vm_addr_align_ok(paddr, dmat->common.alignment))
+ if (paddr != seg_end &&
+ !vm_addr_align_ok(paddr, dmat->common.alignment))
return (true);
return (false);
@@ -476,12 +493,24 @@
* needed in order to complete this transfer
*/
curaddr = buf;
+ /*
+ * Track the expected end of the previous segment so we mirror
+ * load_phys()'s decisions and don't under-count bounces. After
+ * a "would bounce" page, load will have replaced curaddr with a
+ * bounce paddr that won't match the next source paddr; count
+ * simulates that by resetting seg_end to 0 (which no source
+ * paddr can match on modern PPC where page 0 is reserved).
+ */
+ bus_addr_t seg_end = ~(bus_addr_t)0;
while (buflen != 0) {
sgsize = buflen;
- if (must_bounce(dmat, curaddr)) {
+ if (must_bounce(dmat, curaddr, seg_end)) {
sgsize = MIN(sgsize,
PAGE_SIZE - (curaddr & PAGE_MASK));
map->pagesneeded++;
+ seg_end = 0;
+ } else {
+ seg_end = curaddr + sgsize;
}
curaddr += sgsize;
buflen -= sgsize;
@@ -509,6 +538,7 @@
*/
vaddr = (vm_offset_t)buf;
vendaddr = (vm_offset_t)buf + buflen;
+ bus_addr_t seg_end = ~(bus_addr_t)0;
while (vaddr < vendaddr) {
bus_size_t sg_len;
@@ -519,9 +549,12 @@
paddr = pmap_kextract(vaddr);
else
paddr = pmap_extract(pmap, vaddr);
- if (must_bounce(dmat, paddr)) {
+ if (must_bounce(dmat, paddr, seg_end)) {
sg_len = roundup2(sg_len, dmat->common.alignment);
map->pagesneeded++;
+ seg_end = 0;
+ } else {
+ seg_end = paddr + sg_len;
}
vaddr += sg_len;
}
@@ -557,10 +590,12 @@
}
}
+ bus_addr_t seg_end = ~(bus_addr_t)0;
while (buflen > 0) {
curaddr = buf;
sgsize = buflen;
- if (map->pagesneeded != 0 && must_bounce(dmat, curaddr)) {
+ if (map->pagesneeded != 0 &&
+ must_bounce(dmat, curaddr, seg_end)) {
sgsize = MIN(sgsize, PAGE_SIZE - (curaddr & PAGE_MASK));
curaddr = add_bounce_page(dmat, map, 0, curaddr,
sgsize);
@@ -568,6 +603,13 @@
if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
segp))
break;
+ /*
+ * Track the added segment's end so must_bounce() on the next
+ * iteration correctly identifies whether we're continuing a
+ * segment (source contiguous with previous curaddr, which may
+ * itself be a bounce paddr) or starting a new one.
+ */
+ seg_end = curaddr + sgsize;
buf += sgsize;
buflen -= sgsize;
}
@@ -619,6 +661,7 @@
}
vaddr = buf;
+ bus_addr_t seg_end = ~(bus_addr_t)0;
while (buflen > 0) {
/*
@@ -636,7 +679,8 @@
* Compute the segment size, and adjust counts.
*/
sgsize = MIN(buflen, PAGE_SIZE - (curaddr & PAGE_MASK));
- if (map->pagesneeded != 0 && must_bounce(dmat, curaddr)) {
+ if (map->pagesneeded != 0 &&
+ must_bounce(dmat, curaddr, seg_end)) {
sgsize = roundup2(sgsize, dmat->common.alignment);
sgsize = MIN(sgsize, buflen);
curaddr = add_bounce_page(dmat, map, kvaddr, curaddr,
@@ -646,6 +690,13 @@
if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
segp))
break;
+ /*
+ * Track the added segment's end so must_bounce() on the next
+ * iteration correctly identifies whether we're continuing a
+ * segment (source contiguous with previous curaddr, which may
+ * itself be a bounce paddr) or starting a new one.
+ */
+ seg_end = curaddr + sgsize;
vaddr += sgsize;
buflen -= MIN(sgsize, buflen); /* avoid underflow */
}

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