mmc: mmci: add threaded irq to abort DPSM of non-functional state

The stm32_sdmmc variant has build-in support for datatimeout for R1B
requests. If a corresponding IRQ is raised, this triggers the DPSM to stay
busy and remains in a non-functional state. Only a reset can bring it back
to a functional state.

Because a reset must be issued from non-atomic context, let's defer this to
be managed from a threaded IRQ handler. Besides the reset, the threaded
handler also calls mmc_request_done(), to finally complete the request.
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Link: https://lore.kernel.org/r/20191211133934.16932-1-ludovic.Barre@st.com
[Ulf: A few minor updates to the changelog/comments]
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmci.c

@@ -1321,6 +1321,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 	} else if (host->variant->busy_timeout && busy_resp &&
 		   status & MCI_DATATIMEOUT) {
 		cmd->error = -ETIMEDOUT;
+		host->irq_action = IRQ_WAKE_THREAD;
 	} else {
 		cmd->resp[0] = readl(base + MMCIRESPONSE0);
 		cmd->resp[1] = readl(base + MMCIRESPONSE1);
@@ -1339,7 +1340,10 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 				return;
 			}
 		}
-		mmci_request_end(host, host->mrq);
+
+		if (host->irq_action != IRQ_WAKE_THREAD)
+			mmci_request_end(host, host->mrq);
+
 	} else if (sbc) {
 		mmci_start_command(host, host->mrq->cmd, 0);
 	} else if (!host->variant->datactrl_first &&
@@ -1532,9 +1536,9 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
 {
 	struct mmci_host *host = dev_id;
 	u32 status;
-	int ret = 0;
 
 	spin_lock(&host->lock);
+	host->irq_action = IRQ_HANDLED;
 
 	do {
 		status = readl(host->base + MMCISTATUS);
@@ -1574,12 +1578,41 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
 		if (host->variant->busy_detect_flag)
 			status &= ~host->variant->busy_detect_flag;
 
-		ret = 1;
 	} while (status);
 
 	spin_unlock(&host->lock);
 
-	return IRQ_RETVAL(ret);
+	return host->irq_action;
+}
+
+/*
+ * mmci_irq_thread() - A threaded IRQ handler that manages a reset of the HW.
+ *
+ * A reset is needed for some variants, where a datatimeout for a R1B request
+ * causes the DPSM to stay busy (non-functional).
+ */
+static irqreturn_t mmci_irq_thread(int irq, void *dev_id)
+{
+	struct mmci_host *host = dev_id;
+	unsigned long flags;
+
+	if (host->rst) {
+		reset_control_assert(host->rst);
+		udelay(2);
+		reset_control_deassert(host->rst);
+	}
+
+	spin_lock_irqsave(&host->lock, flags);
+	writel(host->clk_reg, host->base + MMCICLOCK);
+	writel(host->pwr_reg, host->base + MMCIPOWER);
+	writel(MCI_IRQENABLE | host->variant->start_err,
+	       host->base + MMCIMASK0);
+
+	host->irq_action = IRQ_HANDLED;
+	mmci_request_end(host, host->mrq);
+	spin_unlock_irqrestore(&host->lock, flags);
+
+	return host->irq_action;
 }
 
 static void mmci_request(struct mmc_host *mmc, struct mmc_request *mrq)
@@ -2063,8 +2096,9 @@ static int mmci_probe(struct amba_device *dev,
 			goto clk_disable;
 	}
 
-	ret = devm_request_irq(&dev->dev, dev->irq[0], mmci_irq, IRQF_SHARED,
-			DRIVER_NAME " (cmd)", host);
+	ret = devm_request_threaded_irq(&dev->dev, dev->irq[0], mmci_irq,
+					mmci_irq_thread, IRQF_SHARED,
+					DRIVER_NAME " (cmd)", host);
 	if (ret)
 		goto clk_disable;
 

drivers/mmc/host/mmci.h

@@ -411,6 +411,7 @@ struct mmci_host {
 
 	struct timer_list	timer;
 	unsigned int		oldstat;
+	u32			irq_action;
 
 	/* pio stuff */
 	struct sg_mapping_iter	sg_miter;