From: Feng Tang <feng.tang@intel.com>
Date: Thu, 21 Jan 2010 02:41:10 +0000 (+0800)
Subject: spi/dw_spi: add a FIFO depth detection
X-Git-Tag: v2.6.34-rc1~290^2~13
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c587b6fa05106606053fc5e8e344f07cd34ace23;p=linux.git

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 f713af8309e3..d948ef4f3910 100644
--- 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)