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busdma: Option to round to cache lines on sync

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Some targets support only flushing or invalidating complete cache lines.
In this cases misaligned buffers might lead to unexpected results. This
patch adds a flag that allows drivers to signal to the bus dma driver
that it is OK to round a buffer to the next full cache line. That's for
example necessary if a driver wants to send out 14 byte via a USB DMA.
Only the driver knows whether these 14 bytes are located in an otherwise
unused cache line aligned buffer.
This commit is contained in:
Christian Mauderer
2020-04-02 16:42:43 +02:00
parent 7e5d93bb6b
commit 4820ccecc9
8 changed files with 81 additions and 0 deletions
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3
rtemsbsd/include/machine/rtems-bsd-bus-dma.h
View File

@@ -75,6 +75,9 @@ struct bus_dma_tag {
struct bus_dmamap {
void *buffer_begin;
bus_size_t buffer_size;
int flags;
/* OK to flush / invalidate the complete cache line */
#define DMAMAP_CACHE_ALIGNED (1 << 0)
};
int

3
rtemsbsd/rtems/rtems-kernel-bus-dma-mbuf.c
View File

@@ -69,6 +69,9 @@ bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
int first = 1;
bus_addr_t lastaddr = 0;
struct mbuf *m;
if ((flags & BUS_DMA_LOAD_MBUF) != 0) {
map->flags |= DMAMAP_CACHE_ALIGNED;
}
for (m = m0; m != NULL && error == 0; m = m->m_next) {
if (m->m_len > 0) {

9
rtemsbsd/rtems/rtems-kernel-bus-dma.c
View File

@@ -365,9 +365,13 @@ bus_dmamap_load(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
map->buffer_begin = buf;
map->buffer_size = buflen;
if ((flags & BUS_DMA_DO_CACHE_LINE_BLOW_UP) != 0) {
map->flags |= DMAMAP_CACHE_ALIGNED;
}
lastaddr = (vm_offset_t)0;
nsegs = 0;
error = bus_dmamap_load_buffer(dmat, dm_segments, buf, buflen,
NULL, flags, &lastaddr, &nsegs, 1);
@@ -397,6 +401,11 @@ bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map, bus_dmasync_op_t op)
uintptr_t begin = (uintptr_t) map->buffer_begin;
uintptr_t end = begin + size;
if ((map->flags & DMAMAP_CACHE_ALIGNED) != 0) {
begin &= ~CLMASK;
end = (end + CLMASK) & ~CLMASK;
size = end - begin;
}
if ((op & BUS_DMASYNC_PREWRITE) != 0 && (op & BUS_DMASYNC_PREREAD) == 0) {
rtems_cache_flush_multiple_data_lines((void *) begin, size);
}