mmc: msm_sdcc: Reset SDCC in case of data transfer errors

SDCC uses an asynchronous FIFOs for data synchronization (one for TX
and one for RX).  For any error when DPSM (Data path state machine) is
involved the transfer is terminated with the remaining data stuck inside
FIFOs. Reset the controller in case of data errors to ensure that
any left over data in FIFOs is flushed out and DPSM is in good state.

The following problems are observed without this reset functionality -

1. After the card is removed in an unsafe way (removed when there
is an on going data transfer), the card will not be detected upon
its next insertion.  This is because the controller wouldn't respond
to few initialization commands.

2. When an error occurs for a data transfer in non-DMA mode, sometimes
we get spurious PIO interrupt after the request is processed.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>

drivers/mmc/host/msm_sdcc.c

@@ -44,6 +44,7 @@
 #include <mach/mmc.h>
 #include <mach/msm_iomap.h>
 #include <mach/dma.h>
+#include <mach/clk.h>
 
 #include "msm_sdcc.h"
 
@@ -126,6 +127,40 @@ static void
 msmsdcc_start_command(struct msmsdcc_host *host, struct mmc_command *cmd,
 		      u32 c);
 
+static void msmsdcc_reset_and_restore(struct msmsdcc_host *host)
+{
+	u32	mci_clk = 0;
+	u32	mci_mask0 = 0;
+	int	ret = 0;
+
+	/* Save the controller state */
+	mci_clk = readl(host->base + MMCICLOCK);
+	mci_mask0 = readl(host->base + MMCIMASK0);
+
+	/* Reset the controller */
+	ret = clk_reset(host->clk, CLK_RESET_ASSERT);
+	if (ret)
+		pr_err("%s: Clock assert failed at %u Hz with err %d\n",
+				mmc_hostname(host->mmc), host->clk_rate, ret);
+
+	ret = clk_reset(host->clk, CLK_RESET_DEASSERT);
+	if (ret)
+		pr_err("%s: Clock deassert failed at %u Hz with err %d\n",
+				mmc_hostname(host->mmc), host->clk_rate, ret);
+
+	pr_info("%s: Controller has been re-initialiazed\n",
+			mmc_hostname(host->mmc));
+
+	/* Restore the contoller state */
+	writel(host->pwr, host->base + MMCIPOWER);
+	writel(mci_clk, host->base + MMCICLOCK);
+	writel(mci_mask0, host->base + MMCIMASK0);
+	ret = clk_set_rate(host->clk, host->clk_rate);
+	if (ret)
+		pr_err("%s: Failed to set clk rate %u Hz (%d)\n",
+				mmc_hostname(host->mmc), host->clk_rate, ret);
+}
+
 static void
 msmsdcc_request_end(struct msmsdcc_host *host, struct mmc_request *mrq)
 {
@@ -223,6 +258,8 @@ msmsdcc_dma_complete_tlet(unsigned long data)
 		pr_err("Flush data: %.8x %.8x %.8x %.8x %.8x %.8x\n",
 		       err.flush[0], err.flush[1], err.flush[2],
 		       err.flush[3], err.flush[4], err.flush[5]);
+
+		msmsdcc_reset_and_restore(host);
 		if (!mrq->data->error)
 			mrq->data->error = -EIO;
 	}
@@ -723,6 +760,7 @@ static void msmsdcc_do_cmdirq(struct msmsdcc_host *host, uint32_t status)
 			msm_dmov_stop_cmd(host->dma.channel,
 					  &host->dma.hdr, 0);
 		else if (host->curr.data) { /* Non DMA */
+			msmsdcc_reset_and_restore(host);
 			msmsdcc_stop_data(host);
 			msmsdcc_request_end(host, cmd->mrq);
 		} else { /* host->data == NULL */
@@ -771,6 +809,7 @@ msmsdcc_handle_irq_data(struct msmsdcc_host *host, u32 status,
 			msm_dmov_stop_cmd(host->dma.channel,
 					  &host->dma.hdr, 0);
 		else {
+			msmsdcc_reset_and_restore(host);
 			if (host->curr.data)
 				msmsdcc_stop_data(host);
 			if (!data->stop)