atmel_serial: keep clock off when it's not needed
The atmel_serial driver is mismanaging its clock by leaving it on at all
times ... the whole point of clock management is to leave it off unless
it's actively needed, which conserves power!!
Although the kernel doesn't actually hang without my fix, it does
discard quite a lot of early console output.
The result still looks correct:
usart users= 1 on 35000000 Hz, for atmel_usart.0
usart users= 0 off 35000000 Hz, for atmel_usart.2
when using ttyS0 as serial console.
[haavard.skinnemoen@atmel.com: Make sure clock is enabled early for console]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 61fb8b6..d5efd6c 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -1258,6 +1258,8 @@
atmel_port->clk = clk_get(&pdev->dev, "usart");
clk_enable(atmel_port->clk);
port->uartclk = clk_get_rate(atmel_port->clk);
+ clk_disable(atmel_port->clk);
+ /* only enable clock when USART is in use */
}
atmel_port->use_dma_rx = data->use_dma_rx;
@@ -1379,6 +1381,8 @@
return -ENODEV;
}
+ clk_enable(atmel_ports[co->index].clk);
+
UART_PUT_IDR(port, -1);
UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
@@ -1403,7 +1407,7 @@
.data = &atmel_uart,
};
-#define ATMEL_CONSOLE_DEVICE &atmel_console
+#define ATMEL_CONSOLE_DEVICE (&atmel_console)
/*
* Early console initialization (before VM subsystem initialized).
@@ -1534,6 +1538,15 @@
if (ret)
goto err_add_port;
+ if (atmel_is_console_port(&port->uart)
+ && ATMEL_CONSOLE_DEVICE->flags & CON_ENABLED) {
+ /*
+ * The serial core enabled the clock for us, so undo
+ * the clk_enable() in atmel_console_setup()
+ */
+ clk_disable(port->clk);
+ }
+
device_init_wakeup(&pdev->dev, 1);
platform_set_drvdata(pdev, port);
@@ -1544,7 +1557,6 @@
port->rx_ring.buf = NULL;
err_alloc_ring:
if (!atmel_is_console_port(&port->uart)) {
- clk_disable(port->clk);
clk_put(port->clk);
port->clk = NULL;
}
@@ -1568,7 +1580,6 @@
/* "port" is allocated statically, so we shouldn't free it */
- clk_disable(atmel_port->clk);
clk_put(atmel_port->clk);
return ret;