mmc: omap_hsmmc: set dto to 14 for all devices

* 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@vger.kernel.org/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@ti.com>

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index b2ccb27..364309c 100644 (file)
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1531,11 +1531,8 @@ 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);
@@ -1543,25 +1540,8 @@ 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;
@@ -1584,13 +1564,13 @@ 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);