[U-Boot] [PATCH v2 2/4] Tegra2: mmc: Support DMA restarts at buffer boundaries

[Anton Staaf]

Currently if a DMA buffer straddles a buffer alignment boundary
(512KiB) then the DMA engine will pause and generate a DMA
interrupt.  Since the DMA interrupt is not enabled it will hang
the MMC driver.

This patch adds support for restarting the DMA transfer.  The
SYSTEM_ADDRESS register contains the next address that would have
been read/written when a boundary is hit.  So we can read that
and write it back.  The write triggers the resumption of the
transfer.

Signed-off-by: Anton Staaf <robotboy at chromium.org>
Cc: Andy Fleming <afleming at gmail.com>
Cc: Tom Warren <twarren at nvidia.com>
Cc: Stephen Warren <swarren at nvidia.com>
Cc: Albert Aribaud <albert.u.boot at aribaud.net>
---
 drivers/mmc/tegra2_mmc.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/tegra2_mmc.c b/drivers/mmc/tegra2_mmc.c
index 2e7746d..73f6405 100644
--- a/drivers/mmc/tegra2_mmc.c
+++ b/drivers/mmc/tegra2_mmc.c
@@ -240,9 +240,16 @@ static int mmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd,
 						__func__, mask);
 				return -1;
 			} else if (mask & TEGRA2_MMC_NORINTSTS_DMA_INTERRUPT) {
-				/* DMA Interrupt */
+				/*
+				 * DMA Interrupt, restart the transfer where
+				 * it was interrupted.
+				 */
+				unsigned int address = readl(&host->reg->sysad);
+
 				debug("DMA end\n");
-				break;
+				writel(TEGRA2_MMC_NORINTSTS_DMA_INTERRUPT,
+				       &host->reg->norintsts);
+				writel(address, &host->reg->sysad);
 			} else if (mask & TEGRA2_MMC_NORINTSTS_XFER_COMPLETE) {
 				/* Transfer Complete */
 				debug("r/w is done\n");
@@ -380,6 +387,7 @@ static int mmc_core_init(struct mmc *mmc)
 	mask |= (1 << 5) | (1 << 4) | (1 << 1) | (1 << 0);
 	mask |= (TEGRA2_MMC_NORINTSTSEN_CMD_COMPLETE |
 		 TEGRA2_MMC_NORINTSTSEN_XFER_COMPLETE |
+		 TEGRA2_MMC_NORINTSTSEN_DMA_INTERRUPT |
 		 TEGRA2_MMC_NORINTSTSEN_BUFFER_WRITE_READY |
 		 TEGRA2_MMC_NORINTSTSEN_BUFFER_READ_READY);
 	writel(mask, &host->reg->norintstsen);
-- 
1.7.3.1