ata: libahci_platform: Add function returning a clock-handle by id

Since all the clocks are retrieved by the method
ahci_platform_get_resources() there is no need for the LLD (glue) drivers
to be looking for some particular of them in the kernel clocks table
again. Instead we suggest to add a simple method returning a
device-specific clock with passed connection ID if it is managed to be
found. Otherwise the function will return NULL. Thus the glue-drivers
won't need to either manually touching the hpriv->clks array or calling
clk_get()-friends. The AHCI platform drivers will be able to use the new
function right after the ahci_platform_get_resources() method invocation
and up to the device removal.

Note the method is left unused here, but will be utilized in the framework
of the DWC AHCI SATA driver being added in the next commit.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

drivers/ata/libahci_platform.c

@@ -93,6 +93,30 @@ void ahci_platform_disable_phys(struct ahci_host_priv *hpriv)
 }
 EXPORT_SYMBOL_GPL(ahci_platform_disable_phys);
 
+/**
+ * ahci_platform_find_clk - Find platform clock
+ * @hpriv: host private area to store config values
+ * @con_id: clock connection ID
+ *
+ * This function returns a pointer to the clock descriptor of the clock with
+ * the passed ID.
+ *
+ * RETURNS:
+ * Pointer to the clock descriptor on success otherwise NULL
+ */
+struct clk *ahci_platform_find_clk(struct ahci_host_priv *hpriv, const char *con_id)
+{
+	int i;
+
+	for (i = 0; i < hpriv->n_clks; i++) {
+		if (!strcmp(hpriv->clks[i].id, con_id))
+			return hpriv->clks[i].clk;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(ahci_platform_find_clk);
+
 /**
  * ahci_platform_enable_clks - Enable platform clocks
  * @hpriv: host private area to store config values

include/linux/ahci_platform.h

@@ -13,6 +13,7 @@
 
 #include <linux/compiler.h>
 
+struct clk;
 struct device;
 struct ata_port_info;
 struct ahci_host_priv;
@@ -21,6 +22,8 @@ struct scsi_host_template;
 
 int ahci_platform_enable_phys(struct ahci_host_priv *hpriv);
 void ahci_platform_disable_phys(struct ahci_host_priv *hpriv);
+struct clk *ahci_platform_find_clk(struct ahci_host_priv *hpriv,
+				   const char *con_id);
 int ahci_platform_enable_clks(struct ahci_host_priv *hpriv);
 void ahci_platform_disable_clks(struct ahci_host_priv *hpriv);
 int ahci_platform_deassert_rsts(struct ahci_host_priv *hpriv);