ata: ahci_brcm: Allow optional reset controller to be used

commit 2b2c47d9 upstream.

On BCM63138, we need to reset the AHCI core prior to start utilizing it,
grab the reset controller device cookie and do that.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/ata/ahci_brcm.c

@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/reset.h>
 #include <linux/string.h>
 
 #include "ahci.h"
@@ -94,6 +95,7 @@ struct brcm_ahci_priv {
 	u32 port_mask;
 	u32 quirks;
 	enum brcm_ahci_version version;
+	struct reset_control *rcdev;
 };
 
 static inline u32 brcm_sata_readreg(void __iomem *addr)
@@ -433,6 +435,11 @@ static int brcm_ahci_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->top_ctrl))
 		return PTR_ERR(priv->top_ctrl);
 
+	/* Reset is optional depending on platform */
+	priv->rcdev = devm_reset_control_get(&pdev->dev, "ahci");
+	if (!IS_ERR_OR_NULL(priv->rcdev))
+		reset_control_deassert(priv->rcdev);
+
 	if ((priv->version == BRCM_SATA_BCM7425) ||
 		(priv->version == BRCM_SATA_NSP)) {
 		priv->quirks |= BRCM_AHCI_QUIRK_NO_NCQ;