mmc: core: Add capability to avoid 3.3V signaling

Some SD host controllers cannot handle extended use of 3.3V signaling.
To accommodate these controllers, add a capability that requires us to
negotiate the voltage down from 3.3V during card initialization.
Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
Signed-off-by: Jennifer Dahm <jennifer.dahm@ni.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/mmc.c

@@ -1830,6 +1830,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	if (host->caps2 & MMC_CAP2_AVOID_3_3V &&
+	    host->ios.signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
+		pr_err("%s: Host failed to negotiate down from 3.3V\n",
+			mmc_hostname(host));
+		err = -EINVAL;
+		goto free_card;
+	}
+
 	if (!oldcard)
 		host->card = card;
 

drivers/mmc/core/sd.c

@@ -1058,6 +1058,14 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
 			mmc_set_bus_width(host, MMC_BUS_WIDTH_4);
 		}
 	}
+
+	if (host->caps2 & MMC_CAP2_AVOID_3_3V &&
+	    host->ios.signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
+		pr_err("%s: Host failed to negotiate down from 3.3V\n",
+			mmc_hostname(host));
+		err = -EINVAL;
+		goto free_card;
+	}
 done:
 	host->card = card;
 	return 0;

drivers/mmc/core/sdio.c

@@ -792,6 +792,14 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
 		if (err)
 			goto remove;
 	}
+
+	if (host->caps2 & MMC_CAP2_AVOID_3_3V &&
+	    host->ios.signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
+		pr_err("%s: Host failed to negotiate down from 3.3V\n",
+			mmc_hostname(host));
+		err = -EINVAL;
+		goto remove;
+	}
 finish:
 	if (!oldcard)
 		host->card = card;

include/linux/mmc/host.h

@@ -354,6 +354,7 @@ struct mmc_host {
 #define MMC_CAP2_NO_MMC		(1 << 22)	/* Do not send (e)MMC commands during initialization */
 #define MMC_CAP2_CQE		(1 << 23)	/* Has eMMC command queue engine */
 #define MMC_CAP2_CQE_DCMD	(1 << 24)	/* CQE can issue a direct command */
+#define MMC_CAP2_AVOID_3_3V	(1 << 25)	/* Host must negotiate down from 3.3V */
 
 	int			fixed_drv_type;	/* fixed driver type for non-removable media */