mmc: mmci: Send a CMD12 to clear the DPSM at errors

The current approach with sending a CMD12 (STOP_TRANSMISSION) to complete a
data transfer request, either because of using the open-ended transmission
type or because of receiving an error during a pre-defined data transfer,
isn't sufficient for the STM32 sdmmc variant. More precisely, this variant
needs to clear the DPSM ("Data Path State Machine") by sending a CMD12, for
all failing ADTC commands.

Support this, by adding a struct mmc_command inside the struct mmci_host
and initialize it to a CMD12 during ->probe(). Let's also add checks for
the new conditions, to enable mmci_data_irq() and mmci_cmd_irq() to
postpone the calls to mmci_request_end(), but instead send the CMD12.

Cc: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Ludovic Barre <ludovic.barre@st.com>

drivers/mmc/host/mmci.c

@@ -1127,6 +1127,12 @@ mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
 	writel(c, base + MMCICOMMAND);
 }
 
+static void mmci_stop_command(struct mmci_host *host)
+{
+	host->stop_abort.error = 0;
+	mmci_start_command(host, &host->stop_abort, 0);
+}
+
 static void
 mmci_data_irq(struct mmci_host *host, struct mmc_data *data,
 	      unsigned int status)
@@ -1196,11 +1202,17 @@ mmci_data_irq(struct mmci_host *host, struct mmc_data *data,
 			/* The error clause is handled above, success! */
 			data->bytes_xfered = data->blksz * data->blocks;
 
-		if (!data->stop || (host->mrq->sbc && !data->error))
-			mmci_request_end(host, data->mrq);
+		if (!data->stop) {
+			if (host->variant->cmdreg_stop && data->error)
+				mmci_stop_command(host);
 			else
+				mmci_request_end(host, data->mrq);
+		} else if (host->mrq->sbc && !data->error) {
+			mmci_request_end(host, data->mrq);
+		} else {
 			mmci_start_command(host, data->stop, 0);
 		}
+	}
 }
 
 static void
@@ -1298,6 +1310,10 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 			mmci_dma_error(host);
 
 			mmci_stop_data(host);
+			if (host->variant->cmdreg_stop && cmd->error) {
+				mmci_stop_command(host);
+				return;
+			}
 		}
 		mmci_request_end(host, host->mrq);
 	} else if (sbc) {
@@ -1956,6 +1972,11 @@ static int mmci_probe(struct amba_device *dev,
 		mmc->max_busy_timeout = 0;
 	}
 
+	/* Prepare a CMD12 - needed to clear the DPSM on some variants. */
+	host->stop_abort.opcode = MMC_STOP_TRANSMISSION;
+	host->stop_abort.arg = 0;
+	host->stop_abort.flags = MMC_RSP_R1B | MMC_CMD_AC;
+
 	mmc->ops = &mmci_ops;
 
 	/* We support these PM capabilities. */

drivers/mmc/host/mmci.h

@@ -377,6 +377,7 @@ struct mmci_host {
 	void __iomem		*base;
 	struct mmc_request	*mrq;
 	struct mmc_command	*cmd;
+	struct mmc_command	stop_abort;
 	struct mmc_data		*data;
 	struct mmc_host		*mmc;
 	struct clk		*clk;