dmaengine: omap-dma: cleanup errata 3.3 handling

Provide a function to read the CSAC/CDAC register, working around the
OMAP 3.2/3.3 erratum (which requires two reads of the register if the
first returned zero.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 29 insertions, 23 deletions

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index a1baada7dcd4..1e0018f36384 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -451,28 +451,39 @@ static size_t omap_dma_desc_size_pos(struct omap_desc *d, dma_addr_t addr)
         return size;
 }
 
+/*
+ * OMAP 3.2/3.3 erratum: sometimes 0 is returned if CSAC/CDAC is
+ * read before the DMA controller finished disabling the channel.
+ */
+static uint32_t omap_dma_chan_read_3_3(struct omap_chan *c, unsigned reg)
+{
+        struct omap_dmadev *od = to_omap_dma_dev(c->vc.chan.device);
+        uint32_t val;
+
+        val = omap_dma_chan_read(c, reg);
+        if (val == 0 && od->plat->errata & DMA_ERRATA_3_3)
+                val = omap_dma_chan_read(c, reg);
+
+        return val;
+}
+
 static dma_addr_t omap_dma_get_src_pos(struct omap_chan *c)
 {
         struct omap_dmadev *od = to_omap_dma_dev(c->vc.chan.device);
-        dma_addr_t addr;
+        dma_addr_t addr, cdac;
 
-        if (__dma_omap15xx(od->plat->dma_attr))
+        if (__dma_omap15xx(od->plat->dma_attr)) {
                 addr = omap_dma_chan_read(c, CPC);
-        else
-                addr = omap_dma_chan_read(c, CSAC);
-
-        if (od->plat->errata & DMA_ERRATA_3_3 && addr == 0)
-                addr = omap_dma_chan_read(c, CSAC);
+        } else {
+                addr = omap_dma_chan_read_3_3(c, CSAC);
+                cdac = omap_dma_chan_read_3_3(c, CDAC);
 
-        if (!__dma_omap15xx(od->plat->dma_attr)) {
                 /*
                  * CDAC == 0 indicates that the DMA transfer on the channel has
                  * not been started (no data has been transferred so far).
                  * Return the programmed source start address in this case.
                  */
-                if (omap_dma_chan_read(c, CDAC))
-                        addr = omap_dma_chan_read(c, CSAC);
-                else
+                if (cdac == 0)
                         addr = omap_dma_chan_read(c, CSSA);
         }
 
@@ -487,21 +498,16 @@ static dma_addr_t omap_dma_get_dst_pos(struct omap_chan *c)
         struct omap_dmadev *od = to_omap_dma_dev(c->vc.chan.device);
         dma_addr_t addr;
 
-        if (__dma_omap15xx(od->plat->dma_attr))
+        if (__dma_omap15xx(od->plat->dma_attr)) {
                 addr = omap_dma_chan_read(c, CPC);
-        else
-                addr = omap_dma_chan_read(c, CDAC);
+        } else {
+                addr = omap_dma_chan_read_3_3(c, CDAC);
 
-        /*
-         * omap 3.2/3.3 erratum: sometimes 0 is returned if CSAC/CDAC is
-         * read before the DMA controller finished disabling the channel.
-         */
-        if (!__dma_omap15xx(od->plat->dma_attr) && addr == 0) {
-                addr = omap_dma_chan_read(c, CDAC);
                 /*
-                 * CDAC == 0 indicates that the DMA transfer on the channel has
-                 * not been started (no data has been transferred so far).
-                 * Return the programmed destination start address in this case.
+                 * CDAC == 0 indicates that the DMA transfer on the channel
+                 * has not been started (no data has been transferred so
+                 * far).  Return the programmed destination start address in
+                 * this case.
                  */
                 if (addr == 0)
                         addr = omap_dma_chan_read(c, CDSA);