mmc: mmci: Enable support for busy detection for ux500 variant

The ux500 variants have HW busy detection support, which is indicated
by the busy_detect flag. For these variants let's enable the
MMC_CAP_WAIT_WHILE_BUSY flag and add the support for it.

The mmc core will provide the RSP_BUSY command flag for those requests
we should care about busy detection. Regarding the max_busy_timeout,
the HW don't support busy detection timeouts so at this initial step
let's make it simple and set it to zero to indicate we are able to
support any timeout.

Cc: Russell King <[e-mail]>
Cc: Johan Rudholm <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/mmci.c

···
 {
 	void __iomem *base = host->base;
 	bool sbc = (cmd == host->mrq->sbc);
+	bool busy_resp = host->variant->busy_detect &&
+			(cmd->flags & MMC_RSP_BUSY);
+
+	/* Check if we need to wait for busy completion. */
+	if (host->busy_status && (status & MCI_ST_CARDBUSY))
+		return;
+
+	/* Enable busy completion if needed and supported. */
+	if (!host->busy_status && busy_resp &&
+		!(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) &&
+		(readl(base + MMCISTATUS) & MCI_ST_CARDBUSY)) {
+		writel(readl(base + MMCIMASK0) | MCI_ST_BUSYEND,
+			base + MMCIMASK0);
+		host->busy_status = status & (MCI_CMDSENT|MCI_CMDRESPEND);
+		return;
+	}
+
+	/* At busy completion, mask the IRQ and complete the request. */
+	if (host->busy_status) {
+		writel(readl(base + MMCIMASK0) & ~MCI_ST_BUSYEND,
+			base + MMCIMASK0);
+		host->busy_status = 0;
+	}
 
 	host->cmd = NULL;
 
···
 			status &= ~MCI_IRQ1MASK;
 		}
 
+		/*
+		 * We intentionally clear the MCI_ST_CARDBUSY IRQ here (if it's
+		 * enabled) since the HW seems to be triggering the IRQ on both
+		 * edges while monitoring DAT0 for busy completion.
+		 */
 		status &= readl(host->base + MMCIMASK0);
 		writel(status, host->base + MMCICLEAR);
 
 		dev_dbg(mmc_dev(host->mmc), "irq0 (data+cmd) %08x\n", status);
 
 		cmd = host->cmd;
-		if (status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT|MCI_CMDSENT|
-			      MCI_CMDRESPEND) && cmd)
+		if ((status|host->busy_status) & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT|
+			MCI_CMDSENT|MCI_CMDRESPEND) && cmd)
 			mmci_cmd_irq(host, cmd, status);
 
 		data = host->data;
···
 			      MCI_TXUNDERRUN|MCI_RXOVERRUN|MCI_DATAEND|
 			      MCI_DATABLOCKEND) && data)
 			mmci_data_irq(host, data, status);
+
+		/* Don't poll for busy completion in irq context. */
+		if (host->busy_status)
+			status &= ~MCI_ST_CARDBUSY;
 
 		ret = 1;
 	} while (status);
···
 		goto clk_disable;
 	}
 
-	if (variant->busy_detect) {
-		mmci_ops.card_busy = mmci_card_busy;
-		mmci_write_datactrlreg(host, MCI_ST_DPSM_BUSYMODE);
-	}
-
-	mmc->ops = &mmci_ops;
 	/*
 	 * The ARM and ST versions of the block have slightly different
 	 * clock divider equations which means that the minimum divider
···
 
 	mmc->caps = plat->capabilities;
 	mmc->caps2 = plat->capabilities2;
+
+	if (variant->busy_detect) {
+		mmci_ops.card_busy = mmci_card_busy;
+		mmci_write_datactrlreg(host, MCI_ST_DPSM_BUSYMODE);
+		mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
+		mmc->max_busy_timeout = 0;
+	}
+
+	mmc->ops = &mmci_ops;
 
 	/* We support these PM capabilities. */
 	mmc->pm_caps = MMC_PM_KEEP_POWER;

drivers/mmc/host/mmci.h

···
 /* Extended status bits for the ST Micro variants */
 #define MCI_ST_SDIOITMASK	(1 << 22)
 #define MCI_ST_CEATAENDMASK	(1 << 23)
+#define MCI_ST_BUSYEND		(1 << 24)
 
 #define MMCIMASK1		0x040
 #define MMCIFIFOCNT		0x048
···
 	u32			pwr_reg;
 	u32			clk_reg;
 	u32			datactrl_reg;
+	u32			busy_status;
 	bool			vqmmc_enabled;
 	struct mmci_platform_data *plat;
 	struct variant_data	*variant;