[PATCH] mmc: omap_hsmmc: set dto to 14 for all devices

[Chase Maupin <Chase.Maupin@xxxxxx>]

* With certain SD cards timeouts like the following have been seen
  due to an improper calculation of the dto value:
    mmcblk0: error -110 transferring data, sector 4126233, nr 8,
    card status 0xc00
* By removing the dto calculation and setting the timeout value
  to the maximum specified by the SD card specification part A2
  section 2.2.15 these timeouts can be avoided.
* This change has been used by beagleboard users as well as the
  Texas Instruments SDK without a negative impact.
* There are multiple discussion threads about this but the most
  relevant ones are:
    * http://talk.maemo.org/showthread.php?p=1000707#post1000707
    * http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg42213.html
* Original proposal for this fix was done by Sukumar Ghoral of
  Texas Instruments

* Tested using a Texas Instruments AM335x EVM

Signed-off-by: Chase Maupin <Chase.Maupin@xxxxxx>
---
 drivers/mmc/host/omap_hsmmc.c |   30 +++++-------------------------
 1 files changed, 5 insertions(+), 25 deletions(-)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index fd0c661..afd7292 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1481,11 +1481,8 @@ static int omap_hsmmc_start_dma_transfer(struct omap_hsmmc_host *host,
 	return 0;
 }
 
-static void set_data_timeout(struct omap_hsmmc_host *host,
-			     unsigned int timeout_ns,
-			     unsigned int timeout_clks)
+static void set_data_timeout(struct omap_hsmmc_host *host)
 {
-	unsigned int timeout, cycle_ns;
 	uint32_t reg, clkd, dto = 0;
 
 	reg = OMAP_HSMMC_READ(host->base, SYSCTL);
@@ -1493,25 +1490,8 @@ static void set_data_timeout(struct omap_hsmmc_host *host,
 	if (clkd == 0)
 		clkd = 1;
 
-	cycle_ns = 1000000000 / (clk_get_rate(host->fclk) / clkd);
-	timeout = timeout_ns / cycle_ns;
-	timeout += timeout_clks;
-	if (timeout) {
-		while ((timeout & 0x80000000) == 0) {
-			dto += 1;
-			timeout <<= 1;
-		}
-		dto = 31 - dto;
-		timeout <<= 1;
-		if (timeout && dto)
-			dto += 1;
-		if (dto >= 13)
-			dto -= 13;
-		else
-			dto = 0;
-		if (dto > 14)
-			dto = 14;
-	}
+    /* Use the maximum timeout value allowed in the standard of 14 or 0xE */
+	dto = 14;
 
 	reg &= ~DTO_MASK;
 	reg |= dto << DTO_SHIFT;
@@ -1534,13 +1514,13 @@ omap_hsmmc_prepare_data(struct omap_hsmmc_host *host, struct mmc_request *req)
 		 * busy signal.
 		 */
 		if (req->cmd->flags & MMC_RSP_BUSY)
-			set_data_timeout(host, 100000000U, 0);
+			set_data_timeout(host);
 		return 0;
 	}
 
 	OMAP_HSMMC_WRITE(host->base, BLK, (req->data->blksz)
 					| (req->data->blocks << 16));
-	set_data_timeout(host, req->data->timeout_ns, req->data->timeout_clks);
+	set_data_timeout(host);
 
 	if (host->use_dma) {
 		ret = omap_hsmmc_start_dma_transfer(host, req);
-- 
1.7.0.4

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