serial: vt8500: UART uses gated clock rather than 24Mhz reference

UART modules on Wondermedia SoCs are connected via a gated clock
source, rather than directly to the 24Mhz reference clock. While
uboot enables UART0 for debugging, other UART ports are unavailable
until the clock is enabled.

This patch checks that a valid clock is actually passed from devicetree,
enables the clock in probe. This change removes the fallback when a
clock was not specified as it doesn't apply any longer (and would only
work if the UART clock was already enabled).

DTSI files are updated for VT8500, WM8505 and WM8650.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 19 insertions, 15 deletions

diff --git a/drivers/tty/serial/vt8500_serial.c b/drivers/tty/serial/vt8500_serial.c
index ff391db0a22..798bf944a2e 100644
--- a/drivers/tty/serial/vt8500_serial.c
+++ b/drivers/tty/serial/vt8500_serial.c
@@ -584,6 +584,23 @@ static int vt8500_serial_probe(struct platform_device *pdev)
 	if (!vt8500_port)
 		return -ENOMEM;
 
+	vt8500_port->uart.membase = devm_request_and_ioremap(&pdev->dev, mmres);
+	if (!vt8500_port->uart.membase)
+		return -EADDRNOTAVAIL;
+
+	vt8500_port->clk = of_clk_get(pdev->dev.of_node, 0);
+	if (IS_ERR(vt8500_port->clk)) {
+		dev_err(&pdev->dev, "failed to get clock\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ret = clk_prepare_enable(vt8500_port->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable clock\n");
+		goto err;
+	}
+
 	vt8500_port->uart.type = PORT_VT8500;
 	vt8500_port->uart.iotype = UPIO_MEM;
 	vt8500_port->uart.mapbase = mmres->start;
@@ -593,25 +610,11 @@ static int vt8500_serial_probe(struct platform_device *pdev)
 	vt8500_port->uart.line = port;
 	vt8500_port->uart.dev = &pdev->dev;
 	vt8500_port->uart.flags = UPF_IOREMAP | UPF_BOOT_AUTOCONF;
-
-	vt8500_port->clk = of_clk_get(pdev->dev.of_node, 0);
-	if (vt8500_port->clk) {
-		vt8500_port->uart.uartclk = clk_get_rate(vt8500_port->clk);
-	} else {
-		/* use the default of 24Mhz if not specified and warn */
-		pr_warn("%s: serial clock source not specified\n", __func__);
-		vt8500_port->uart.uartclk = 24000000;
-	}
+	vt8500_port->uart.uartclk = clk_get_rate(vt8500_port->clk);
 
 	snprintf(vt8500_port->name, sizeof(vt8500_port->name),
 		 "VT8500 UART%d", pdev->id);
 
-	vt8500_port->uart.membase = devm_request_and_ioremap(&pdev->dev, mmres);
-	if (!vt8500_port->uart.membase) {
-		ret = -EADDRNOTAVAIL;
-		goto err;
-	}
-
 	vt8500_uart_ports[port] = vt8500_port;
 
 	uart_add_one_port(&vt8500_uart_driver, &vt8500_port->uart);
@@ -630,6 +633,7 @@ static int vt8500_serial_remove(struct platform_device *pdev)
 	struct vt8500_port *vt8500_port = platform_get_drvdata(pdev);
 
 	platform_set_drvdata(pdev, NULL);
+	clk_disable_unprepare(vt8500_port->clk);
 	uart_remove_one_port(&vt8500_uart_driver, &vt8500_port->uart);
 	kfree(vt8500_port);