[PATCH] sdhci: work around broken dma boundary behaviour

[Mikko Vinni <mmvinni@yahoo.com>]

Some SD host controllers (noticed on an integrated JMicron SD reader
on an HP Pavilion dv5-1250eo laptop) don't update the dma address
register before signalling a dma interrupt due to a dma boundary.
Detect this and update the register to the next 512KB boundary,
at which the transfer presumably stopped. As long as each transfer
is at most 512KB in size (on this hardware the max seems to be
65536 bytes), this fix is neeeded at most once per transfer.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=28462

Signed-off-by: Mikko Vinni <mmvinni@yahoo.com>

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index a25db42..469cf74 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1537,9 +1537,27 @@ static void sdhci_data_irq(struct sdhci_host *host, u32
intmask)
 		 * boundaries, but as we can't disable the feature
 		 * we need to at least restart the transfer.
 		 */
-		if (intmask & SDHCI_INT_DMA_END)
-			sdhci_writel(host, sdhci_readl(host, SDHCI_DMA_ADDRESS),
-				SDHCI_DMA_ADDRESS);
+		if (intmask & SDHCI_INT_DMA_END) {
+			u32 dmastart, dmanow;
+			dmastart = sg_dma_address(host->data->sg);
+			dmanow = sdhci_readl(host, SDHCI_DMA_ADDRESS);
+			if (dmanow == dmastart) {
+				/*
+				 * HW failed to increase the address.
+				 * Update to the next 512KB block boundary.
+				 */
+				dmanow = (dmanow & ~0x7ffff) + 0x80000;
+				if (dmanow > dmastart + host->data->blksz *
+							host->data->blocks) {
+					WARN_ON(1);
+					dmanow = dmastart;
+				}
+				DBG("%s: next DMA address forced "
+				    "from 0x%08x to 0x%08x\n",
+				    mmc_hostname(host->mmc), dmastart, dmanow);
+			}
+			sdhci_writel(host, dmanow, SDHCI_DMA_ADDRESS);
+		}
 
 		if (intmask & SDHCI_INT_DATA_END) {
 			if (host->cmd) {