ata: ahci: ceva: Update the driver to support xilinx GT phy

SATA controller used in Xilinx ZynqMP platform uses xilinx GT phy
which has 4 GT lanes and can be used by 4 peripherals at a time.
SATA controller uses 1 GT phy lane among the 4 GT lanes. To configure
the GT lane for the SATA controller, the below sequence is expected.

1. Assert the SATA controller reset.
2. Configure the xilinx GT phy lane for SATA controller (phy_init).
3. De-assert the SATA controller reset.
4. Wait for PLL of the GT lane used by SATA to be locked (phy_power_on).

The ahci_platform_enable_resources() by default does the phy_init()
and phy_power_on() but the default sequence doesn't work with Xilinx
platforms. Because of this reason, updated the driver to support the
new sequence.

Added cevapriv->rst check, for backward compatibility with the older
sequence. If the reset controller is not available, then the SATA
controller will configure with the older sequences.

Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Piyush Mehta

drivers/ata/ahci_ceva.c

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
+#include <linux/reset.h>
 #include "ahci.h"
 
 /* Vendor Specific Register Offsets */
@@ -87,6 +88,7 @@ struct ceva_ahci_priv {
 	u32 axicc;
 	bool is_cci_enabled;
 	int flags;
+	struct reset_control *rst;
 };
 
 static unsigned int ceva_ahci_read_id(struct ata_device *dev,
@@ -202,13 +204,48 @@ static int ceva_ahci_probe(struct platform_device *pdev)
 
 	cevapriv->ahci_pdev = pdev;
 
+	cevapriv->rst = devm_reset_control_get_optional_exclusive(&pdev->dev,
+								  NULL);
+	if (IS_ERR(cevapriv->rst)) {
+		if (PTR_ERR(cevapriv->rst) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "failed to get reset: %ld\n",
+				PTR_ERR(cevapriv->rst));
+	}
+
 	hpriv = ahci_platform_get_resources(pdev, 0);
 	if (IS_ERR(hpriv))
 		return PTR_ERR(hpriv);
 
-	rc = ahci_platform_enable_resources(hpriv);
-	if (rc)
-		return rc;
+	if (!cevapriv->rst) {
+		rc = ahci_platform_enable_resources(hpriv);
+		if (rc)
+			return rc;
+	} else {
+		int i;
+
+		rc = ahci_platform_enable_clks(hpriv);
+		if (rc)
+			return rc;
+		/* Assert the controller reset */
+		reset_control_assert(cevapriv->rst);
+
+		for (i = 0; i < hpriv->nports; i++) {
+			rc = phy_init(hpriv->phys[i]);
+			if (rc)
+				return rc;
+		}
+
+		/* De-assert the controller reset */
+		reset_control_deassert(cevapriv->rst);
+
+		for (i = 0; i < hpriv->nports; i++) {
+			rc = phy_power_on(hpriv->phys[i]);
+			if (rc) {
+				phy_exit(hpriv->phys[i]);
+				return rc;
+			}
+		}
+	}
 
 	if (of_property_read_bool(np, "ceva,broken-gen2"))
 		cevapriv->flags = CEVA_FLAG_BROKEN_GEN2;