[U-Boot] regression on emmc: board db410c

[Jorge Ramirez]

Hi all,

I just noticed that commit [1]  breaks e-mmc support for db410c.
If you need emmc access you can work around it by reducing the timeout 
on completion (to just a few tenths of usecs) and returning 0 instead of 
-ETIMEDOUT.

I am trying to understand why the condition is not met as per the spec. 
[2] (register descriptions on page 85,86 ..). Feel free to comment.

thanks
Jorge


[1]
[jramirez at igloo git.uboot (master $)]$ git show 
7dde50d70787eb2faeced82d0c025762b12363ea
commit 7dde50d70787eb2faeced82d0c025762b12363ea
Author: Alex Deymo <deymo at google.com>
Date:   Sun Apr 2 01:24:34 2017 -0700

     mmc: sdhci: Wait for SDHCI_INT_DATA_END when transferring.

     sdhci_transfer_data() function transfers the blocks passed up to the
     number of blocks defined in mmc_data, but returns immediately once all
     the blocks are transferred, even if the loop exit condition is not met
     (bit SDHCI_INT_DATA_END set in the STATUS word).

     When doing multiple writes to mmc, returning right after the last 
block
     is transferred can cause the write to fail when sending the
     MMC_CMD_STOP_TRANSMISSION command right after the
     MMC_CMD_WRITE_MULTIPLE_BLOCK command, leaving the mmc driver in an
     unconsistent state until reboot. This error was observed in the rpi3
     board.

     This patch waits for the SDHCI_INT_DATA_END bit to be set even after
     sending all the blocks.

     Test: Reliably wrote 2GiB of data to mmc in a rpi3.

     Signed-off-by: Alex Deymo <deymo at google.com>
     Reviewed-by: Simon Glass <sjg at chromium.org>

diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c
index c94d58d..b745977 100644
--- a/drivers/mmc/sdhci.c
+++ b/drivers/mmc/sdhci.c
@@ -72,6 +72,7 @@ static int sdhci_transfer_data(struct sdhci_host 
*host, struct mmc_data *data,
                                 unsigned int start_addr)
  {
         unsigned int stat, rdy, mask, timeout, block = 0;
+ bool transfer_done = false;
  #ifdef CONFIG_MMC_SDHCI_SDMA
         unsigned char ctrl;
         ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
@@ -89,17 +90,23 @@ static int sdhci_transfer_data(struct sdhci_host 
*host, struct mmc_data *data,
                                __func__, stat);
                         return -EIO;
                 }
-           if (stat & rdy) {
+         if (!transfer_done && (stat & rdy)) {
                         if (!(sdhci_readl(host, SDHCI_PRESENT_STATE) & 
mask))
                                 continue;
                         sdhci_writel(host, rdy, SDHCI_INT_STATUS);
                         sdhci_transfer_pio(host, data);
                         data->dest += data->blocksize;
-                   if (++block >= data->blocks)
-                           break;
+                 if (++block >= data->blocks) {
+                         /* Keep looping until the SDHCI_INT_DATA_END is
+                          * cleared, even if we finished sending all the
+                          * blocks.
+                          */
+                         transfer_done = true;
+                         continue;
+                 }
                 }
  #ifdef CONFIG_MMC_SDHCI_SDMA
-           if (stat & SDHCI_INT_DMA_END) {
+         if (!transfer_done && (stat & SDHCI_INT_DMA_END)) {
                         sdhci_writel(host, SDHCI_INT_DMA_END, 
SDHCI_INT_STATUS);
                         start_addr &= ~(SDHCI_DEFAULT_BOUNDARY_SIZE - 1);
                         start_addr += SDHCI_DEFAULT_BOUNDARY_SIZE;

[2] 
https://www.sdcard.org/downloads/pls/pdf/index.php?p=PartA2_SD%20Host_Controller_Simplified_Specification_Ver4.20.jpg&f=PartA2_SD%20Host_Controller_Simplified_Specification_Ver4.20.pdf&e=EN_SSA2