ata: ahci: Introduce firmware-specific caps initialization

There are systems with no BIOS or comprehensive embedded firmware which
could be able to properly initialize the SATA AHCI controller
platform-specific capabilities. In that case a good alternative to having
a clever bootloader is to create a device tree node with the properties
well describing all the AHCI-related platform specifics. All the settings
which are normally detected and marked as available in the HBA and its
ports capabilities fields [1] could be defined in the platform DTB by
means of a set of the dedicated properties. Such approach perfectly fits
to the DTB-philosophy - to provide hardware/platform description.

So here we suggest to extend the SATA AHCI device tree bindings with two
additional DT-properties:
1) "hba-cap" - HBA platform generic capabilities like:
   - SSS - Staggered Spin-up support.
   - SMPS - Mechanical Presence Switch support.
2) "hba-port-cap" - HBA platform port capabilities like:
   - HPCP - Hot Plug Capable Port.
   - MPSP - Mechanical Presence Switch Attached to Port.
   - CPD - Cold Presence Detection.
   - ESP - External SATA Port.
   - FBSCP - FIS-based Switching Capable Port.
All of these capabilities require to have a corresponding hardware
configuration. Thus it's ok to have them defined in DTB.

Even though the driver currently takes into account the state of the ESP
and FBSCP flags state only, there is nothing wrong with having all of them
supported by the generic AHCI library in order to have a complete OF-based
platform-capabilities initialization procedure. These properties will be
parsed in the ahci_platform_get_resources() method and their values will
be stored in the saved_* fields of the ahci_host_priv structure, which in
its turn then will be used to restore the H.CAP, H.PI and P#.CMD
capability fields on device init and after HBA reset.

Please note this modification concerns the HW-init HBA and its ports flags
only, which are by specification [1] are supposed to be initialized by the
BIOS/platform firmware/expansion ROM and which are normally declared in
the one-time-writable-after-reset register fields. Even though these flags
aren't supposed to be cleared after HBA reset some AHCI instances may
violate that rule so we still need to perform the fields resetting after
each reset. Luckily the corresponding functionality has already been
partly implemented in the framework of the ahci_save_initial_config() and
ahci_restore_initial_config() methods.

[1] Serial ATA AHCI 1.3.1 Specification, p. 103
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

drivers/ata/ahci.h

@@ -338,6 +338,7 @@ struct ahci_host_priv {
 	u32			saved_cap;	/* saved initial cap */
 	u32			saved_cap2;	/* saved initial cap2 */
 	u32			saved_port_map;	/* saved initial port_map */
+	u32			saved_port_cap[AHCI_MAX_PORTS]; /* saved port_cap */
 	u32 			em_loc; /* enclosure management location */
 	u32			em_buf_sz;	/* EM buffer size in byte */
 	u32			em_msg_type;	/* EM message type */

drivers/ata/libahci.c

@@ -16,6 +16,7 @@
  * http://www.intel.com/technology/serialata/pdf/rev1_1.pdf
  */
 
+#include <linux/bitops.h>
 #include <linux/kernel.h>
 #include <linux/gfp.h>
 #include <linux/module.h>
@@ -443,16 +444,28 @@ static ssize_t ahci_show_em_supported(struct device *dev,
 void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 {
 	void __iomem *mmio = hpriv->mmio;
-	u32 cap, cap2, vers, port_map;
+	void __iomem *port_mmio;
+	unsigned long port_map;
+	u32 cap, cap2, vers;
 	int i;
 
 	/* make sure AHCI mode is enabled before accessing CAP */
 	ahci_enable_ahci(mmio);
 
-	/* Values prefixed with saved_ are written back to host after
-	 * reset.  Values without are used for driver operation.
+	/*
+	 * Values prefixed with saved_ are written back to the HBA and ports
+	 * registers after reset. Values without are used for driver operation.
+	 */
+
+	/*
+	 * Override HW-init HBA capability fields with the platform-specific
+	 * values. The rest of the HBA capabilities are defined as Read-only
+	 * and can't be modified in CSR anyway.
 	 */
-	hpriv->saved_cap = cap = readl(mmio + HOST_CAP);
+	cap = readl(mmio + HOST_CAP);
+	if (hpriv->saved_cap)
+		cap = (cap & ~(HOST_CAP_SSS | HOST_CAP_MPS)) | hpriv->saved_cap;
+	hpriv->saved_cap = cap;
 
 	/* CAP2 register is only defined for AHCI 1.2 and later */
 	vers = readl(mmio + HOST_VERSION);
@@ -519,7 +532,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 	/* Override the HBA ports mapping if the platform needs it */
 	port_map = readl(mmio + HOST_PORTS_IMPL);
 	if (hpriv->saved_port_map && port_map != hpriv->saved_port_map) {
-		dev_info(dev, "forcing port_map 0x%x -> 0x%x\n",
+		dev_info(dev, "forcing port_map 0x%lx -> 0x%x\n",
 			 port_map, hpriv->saved_port_map);
 		port_map = hpriv->saved_port_map;
 	} else {
@@ -527,7 +540,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 	}
 
 	if (hpriv->mask_port_map) {
-		dev_warn(dev, "masking port_map 0x%x -> 0x%x\n",
+		dev_warn(dev, "masking port_map 0x%lx -> 0x%lx\n",
 			port_map,
 			port_map & hpriv->mask_port_map);
 		port_map &= hpriv->mask_port_map;
@@ -546,7 +559,7 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 		 */
 		if (map_ports > ahci_nr_ports(cap)) {
 			dev_warn(dev,
-				 "implemented port map (0x%x) contains more ports than nr_ports (%u), using nr_ports\n",
+				 "implemented port map (0x%lx) contains more ports than nr_ports (%u), using nr_ports\n",
 				 port_map, ahci_nr_ports(cap));
 			port_map = 0;
 		}
@@ -555,12 +568,26 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 	/* fabricate port_map from cap.nr_ports for < AHCI 1.3 */
 	if (!port_map && vers < 0x10300) {
 		port_map = (1 << ahci_nr_ports(cap)) - 1;
-		dev_warn(dev, "forcing PORTS_IMPL to 0x%x\n", port_map);
+		dev_warn(dev, "forcing PORTS_IMPL to 0x%lx\n", port_map);
 
 		/* write the fixed up value to the PI register */
 		hpriv->saved_port_map = port_map;
 	}
 
+	/*
+	 * Preserve the ports capabilities defined by the platform. Note there
+	 * is no need in storing the rest of the P#.CMD fields since they are
+	 * volatile.
+	 */
+	for_each_set_bit(i, &port_map, AHCI_MAX_PORTS) {
+		if (hpriv->saved_port_cap[i])
+			continue;
+
+		port_mmio = __ahci_port_base(hpriv, i);
+		hpriv->saved_port_cap[i] =
+			readl(port_mmio + PORT_CMD) & PORT_CMD_CAP;
+	}
+
 	/* record values to use during operation */
 	hpriv->cap = cap;
 	hpriv->cap2 = cap2;
@@ -590,13 +617,21 @@ EXPORT_SYMBOL_GPL(ahci_save_initial_config);
 static void ahci_restore_initial_config(struct ata_host *host)
 {
 	struct ahci_host_priv *hpriv = host->private_data;
+	unsigned long port_map = hpriv->port_map;
 	void __iomem *mmio = hpriv->mmio;
+	void __iomem *port_mmio;
+	int i;
 
 	writel(hpriv->saved_cap, mmio + HOST_CAP);
 	if (hpriv->saved_cap2)
 		writel(hpriv->saved_cap2, mmio + HOST_CAP2);
 	writel(hpriv->saved_port_map, mmio + HOST_PORTS_IMPL);
 	(void) readl(mmio + HOST_PORTS_IMPL);	/* flush */
+
+	for_each_set_bit(i, &port_map, AHCI_MAX_PORTS) {
+		port_mmio = __ahci_port_base(hpriv, i);
+		writel(hpriv->saved_port_cap[i], port_mmio + PORT_CMD);
+	}
 }
 
 static unsigned ahci_scr_offset(struct ata_port *ap, unsigned int sc_reg)

drivers/ata/libahci_platform.c

@@ -382,6 +382,34 @@ static int ahci_platform_get_regulator(struct ahci_host_priv *hpriv, u32 port,
 	return rc;
 }
 
+static int ahci_platform_get_firmware(struct ahci_host_priv *hpriv,
+				      struct device *dev)
+{
+	struct device_node *child;
+	u32 port;
+
+	if (!of_property_read_u32(dev->of_node, "hba-cap", &hpriv->saved_cap))
+		hpriv->saved_cap &= (HOST_CAP_SSS | HOST_CAP_MPS);
+
+	of_property_read_u32(dev->of_node,
+			     "ports-implemented", &hpriv->saved_port_map);
+
+	for_each_child_of_node(dev->of_node, child) {
+		if (!of_device_is_available(child))
+			continue;
+
+		if (of_property_read_u32(child, "reg", &port)) {
+			of_node_put(child);
+			return -EINVAL;
+		}
+
+		if (!of_property_read_u32(child, "hba-port-cap", &hpriv->saved_port_cap[port]))
+			hpriv->saved_port_cap[port] &= PORT_CMD_CAP;
+	}
+
+	return 0;
+}
+
 /**
  * ahci_platform_get_resources - Get platform resources
  * @pdev: platform device to get resources for
@@ -525,9 +553,6 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
 		goto err_out;
 	}
 
-	of_property_read_u32(dev->of_node,
-			     "ports-implemented", &hpriv->saved_port_map);
-
 	if (child_nodes) {
 		for_each_child_of_node(dev->of_node, child) {
 			u32 port;
@@ -592,6 +617,15 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
 		if (rc == -EPROBE_DEFER)
 			goto err_out;
 	}
+
+	/*
+	 * Retrieve firmware-specific flags which then will be used to set
+	 * the HW-init fields of HBA and its ports
+	 */
+	rc = ahci_platform_get_firmware(hpriv, dev);
+	if (rc)
+		goto err_out;
+
 	pm_runtime_enable(dev);
 	pm_runtime_get_sync(dev);
 	hpriv->got_runtime_pm = true;