usb: host: xhci-plat: Add reset support

Add optional reset support. This is in preparation to adding USB xHCI
support for RZ/V2M SoC.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230121145853.4792-9-biju.das.jz@bp.renesas.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-plat.c

@@ -19,6 +19,7 @@
 #include <linux/slab.h>
 #include <linux/acpi.h>
 #include <linux/usb/of.h>
+#include <linux/reset.h>
 
 #include "xhci.h"
 #include "xhci-plat.h"
@@ -263,10 +264,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
 		goto put_hcd;
 	}
 
-	ret = clk_prepare_enable(xhci->reg_clk);
+	xhci->reset = devm_reset_control_array_get_optional_shared(&pdev->dev);
+	if (IS_ERR(xhci->reset)) {
+		ret = PTR_ERR(xhci->reset);
+		goto put_hcd;
+	}
+
+	ret = reset_control_deassert(xhci->reset);
 	if (ret)
 		goto put_hcd;
 
+	ret = clk_prepare_enable(xhci->reg_clk);
+	if (ret)
+		goto err_reset;
+
 	ret = clk_prepare_enable(xhci->clk);
 	if (ret)
 		goto disable_reg_clk;
@@ -377,6 +388,9 @@ static int xhci_plat_probe(struct platform_device *pdev)
 disable_reg_clk:
 	clk_disable_unprepare(xhci->reg_clk);
 
+err_reset:
+	reset_control_assert(xhci->reset);
+
 put_hcd:
 	usb_put_hcd(hcd);
 
@@ -412,6 +426,7 @@ static int xhci_plat_remove(struct platform_device *dev)
 
 	clk_disable_unprepare(clk);
 	clk_disable_unprepare(reg_clk);
+	reset_control_assert(xhci->reset);
 	usb_put_hcd(hcd);
 
 	pm_runtime_disable(&dev->dev);