spi/dw_spi: add a FIFO depth detection

FIFO depth is configurable for each implementation of DW core,
so add a depth detection for those interface drivers who don't set
the fifo_len explicitly

Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Jean-Hugues Deschenes <jean-hugues.deschenes@octasic.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index f713af8309e3a093a65847a8f4de0dd77808632e..d948ef4f3910bcd9f8f1b876eb3cfb0c610e295e 100644 (file)
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -831,6 +831,22 @@ static void spi_hw_init(struct dw_spi *dws)
        spi_mask_intr(dws, 0xff);
        spi_enable_chip(dws, 1);
        flush(dws);
+
+       /*
+        * Try to detect the FIFO depth if not set by interface driver,
+        * the depth could be from 2 to 256 from HW spec
+        */
+       if (!dws->fifo_len) {
+               u32 fifo;
+               for (fifo = 2; fifo <= 257; fifo++) {
+                       dw_writew(dws, txfltr, fifo);
+                       if (fifo != dw_readw(dws, txfltr))
+                               break;
+               }
+
+               dws->fifo_len = (fifo == 257) ? 0 : fifo;
+               dw_writew(dws, txfltr, 0);
+       }
 }
 
 int __devinit dw_spi_add_host(struct dw_spi *dws)