[PATCH AUTOSEL 4.19 11/13] MIPS: Alchemy: fix dbdma2

Sasha Levin
2023-05-31T13:53:34Z

From: Manuel Lauss <manuel.lauss@gmail.com>

[ Upstream commit 2d645604f69f3a772d58ead702f9a8e84ab2b342 ]

Various fixes for the Au1200/Au1550/Au1300 DBDMA2 code:

- skip cache invalidation if chip has working coherency circuitry.
- invalidate KSEG0-portion of the (physical) data address.
- force the dma channel doorbell write out to bus immediately with
a sync.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/mips/alchemy/common/dbdma.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/arch/mips/alchemy/common/dbdma.c b/arch/mips/alchemy/common/dbdma.c
index 4ca2c28878e0f..e9ee9ab90a0c6 100644
--- a/arch/mips/alchemy/common/dbdma.c
+++ b/arch/mips/alchemy/common/dbdma.c
@@ -30,6 +30,7 @@
*
*/

+#include <linux/dma-map-ops.h> /* for dma_default_coherent */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
@@ -623,17 +624,18 @@ u32 au1xxx_dbdma_put_source(u32 chanid, dma_addr_t buf, int nbytes, u32 flags)
dp->dscr_cmd0 &= ~DSCR_CMD0_IE;

/*
- * There is an errata on the Au1200/Au1550 parts that could result
- * in "stale" data being DMA'ed. It has to do with the snoop logic on
- * the cache eviction buffer. DMA_NONCOHERENT is on by default for
- * these parts. If it is fixed in the future, these dma_cache_inv will
- * just be nothing more than empty macros. See io.h.
+ * There is an erratum on certain Au1200/Au1550 revisions that could
+ * result in "stale" data being DMA'ed. It has to do with the snoop
+ * logic on the cache eviction buffer. dma_default_coherent is set
+ * to false on these parts.
*/
- dma_cache_wback_inv((unsigned long)buf, nbytes);
+ if (!dma_default_coherent)
+ dma_cache_wback_inv(KSEG0ADDR(buf), nbytes);
dp->dscr_cmd0 |= DSCR_CMD0_V; /* Let it rip */
wmb(); /* drain writebuffer */
dma_cache_wback_inv((unsigned long)dp, sizeof(*dp));
ctp->chan_ptr->ddma_dbell = 0;
+ wmb(); /* force doorbell write out to dma engine */

/* Get next descriptor pointer. */
ctp->put_ptr = phys_to_virt(DSCR_GET_NXTPTR(dp->dscr_nxtptr));
@@ -685,17 +687,18 @@ u32 au1xxx_dbdma_put_dest(u32 chanid, dma_addr_t buf, int nbytes, u32 flags)
dp->dscr_source1, dp->dscr_dest0, dp->dscr_dest1);
#endif
/*
- * There is an errata on the Au1200/Au1550 parts that could result in
- * "stale" data being DMA'ed. It has to do with the snoop logic on the
- * cache eviction buffer. DMA_NONCOHERENT is on by default for these
- * parts. If it is fixed in the future, these dma_cache_inv will just
- * be nothing more than empty macros. See io.h.
+ * There is an erratum on certain Au1200/Au1550 revisions that could
+ * result in "stale" data being DMA'ed. It has to do with the snoop
+ * logic on the cache eviction buffer. dma_default_coherent is set
+ * to false on these parts.
*/
- dma_cache_inv((unsigned long)buf, nbytes);
+ if (!dma_default_coherent)
+ dma_cache_inv(KSEG0ADDR(buf), nbytes);
dp->dscr_cmd0 |= DSCR_CMD0_V; /* Let it rip */
wmb(); /* drain writebuffer */
dma_cache_wback_inv((unsigned long)dp, sizeof(*dp));
ctp->chan_ptr->ddma_dbell = 0;
+ wmb(); /* force doorbell write out to dma engine */

/* Get next descriptor pointer. */
ctp->put_ptr = phys_to_virt(DSCR_GET_NXTPTR(dp->dscr_nxtptr));
--
2.39.2