[arm/tegra]serial: Power control api for bluesleep power management.

Adding apis for following function to hooking up tegra serial driver with
bluesleep power management:
- Clock off.
- Clock on.
- Setting flow control to desired state.
- Checking for tx fifo status.

Following 4 state of uart state machine is developed to achieve this:
UART_CLOSED, UART_OPENED, UART_SUSPEND, UART_CLOCK_OFF.

The transitions of states are as follows:
UART_CLOSED: the init state  on which resource is allocated but not
             opened by client or when device is closed.

UART_OPENED: Able to do data transfer.
             CLOSED  to  OPENED by opening the port.
             CLOCK_OFF to OPENED by calling function tegra_uart_request_clock_on().
             SUSPEND to OPENED by calling resume().

UART_CLOCK_OFF: The controller clock is disabled and so no data transfer
                can happen. At this state, controller is not ready for
                deep power down.
             OPENED to CLOCK_OFF by calling tegra_uart_request_clock_off().
             Can not go to this state from CLOSED and SUSPEND.

UART_SUSPEND: The controller is in suspended state and ready for deep power down.
             UART_CLOCK_OFF to SUSPEND:
             OPENED to SUSPEND.

Change-Id: Ib0c40547665181cadd172840be9aed2cc18ba448
Reviewed-on: http://git-master/r/2819
Reviewed-by: Anantha Idapalapati <aidapalapati@nvidia.com>
Tested-by: Anantha Idapalapati <aidapalapati@nvidia.com>
Reviewed-by: Udaykumar Rameshchan Raval <uraval@nvidia.com>
Reviewed-by: Gary King <gking@nvidia.com>

2 files changed, 107 insertions, 2 deletions

diff --git a/arch/arm/mach-tegra/include/mach/serial.h b/arch/arm/mach-tegra/include/mach/serial.h
index c77afa190998..fb4c92a9902c 100644
--- a/arch/arm/mach-tegra/include/mach/serial.h
+++ b/arch/arm/mach-tegra/include/mach/serial.h
@@ -24,6 +24,7 @@
 
 #include <linux/types.h>
 #include <linux/serial_8250.h>
+#include <linux/serial_core.h>
 
 #include <mach/pinmux.h>
 
@@ -33,4 +34,18 @@ struct tegra_serial_platform_data {
 	int nr_pins;
 };
 
+/* Switch off the clock of the uart controller. */
+void tegra_uart_request_clock_off(struct uart_port *uport);
+
+/* Switch on the clock of the uart controller */
+void tegra_uart_request_clock_on(struct uart_port *uport);
+
+/* Set the modem control signals state of uart controller. */
+void tegra_uart_set_mctrl(struct uart_port *uport, unsigned int mctrl);
+
+/* Return the status of the transmit fifo whether empty or not.
+ * Return 0 if tx fifo is not empty.
+ * Return TIOCSER_TEMT if tx fifo is empty */
+int tegra_uart_is_tx_empty(struct uart_port *uport);
+
 #endif
diff --git a/drivers/serial/tegra_hsuart.c b/drivers/serial/tegra_hsuart.c
index 77fc79037b62..39a6035e9955 100644
--- a/drivers/serial/tegra_hsuart.c
+++ b/drivers/serial/tegra_hsuart.c
@@ -75,6 +75,11 @@ const int dma_req_sel[] = {
 #define TEGRA_UART_MIN_DMA		16
 #define TEGRA_UART_FIFO_SIZE		8
 
+#define TEGRA_UART_CLOSED    0
+#define TEGRA_UART_OPENED    1
+#define TEGRA_UART_CLOCK_OFF 2
+#define TEGRA_UART_SUSPEND   3
+
 struct tegra_uart_port {
 	struct uart_port	uport;
 	char			port_name[32];
@@ -112,6 +117,7 @@ struct tegra_uart_port {
 	bool			use_tx_dma;
 
 	bool			rx_timeout;
+	int uart_state;
 };
 
 static inline u8 uart_readb(struct tegra_uart_port *t, unsigned long reg)
@@ -539,6 +545,7 @@ static void tegra_uart_hw_deinit(struct tegra_uart_port *t)
 	t->baud = 0;
 	if (t->pinmux)
 		tegra_pinmux_config_tristate_table(t->pinmux, t->nr_pins, TEGRA_TRI_TRISTATE);
+	t->uart_state = TEGRA_UART_CLOSED;
 }
 
 static void tegra_uart_free_rx_dma(struct tegra_uart_port *t)
@@ -659,6 +666,7 @@ static int tegra_uart_hw_init(struct tegra_uart_port *t)
 	t->ier_shadow = ier;
 	uart_writeb(t, ier, UART_IER);
 
+	t->uart_state = TEGRA_UART_OPENED;
 	dev_vdbg(t->uport.dev, "-tegra_uart_hw_init\n");
 	return 0;
 }
@@ -1123,10 +1131,18 @@ static int tegra_uart_suspend(struct platform_device *pdev, pm_message_t state)
 
 	dev_err(t->uport.dev, "tegra_uart_suspend called\n");
 	u = &t->uport;
+
+	/* Enable clock before calling suspend so that controller
+	   register can be accessible */
+	if (t->uart_state == TEGRA_UART_CLOCK_OFF) {
+		clk_enable(t->clk);
+		t->uart_state = TEGRA_UART_OPENED;
+	}
+
 	uart_suspend_port(&tegra_uart_driver, u);
 	if (t->pinmux)
 		tegra_pinmux_config_tristate_table(t->pinmux, t->nr_pins, TEGRA_TRI_TRISTATE);
-
+	t->uart_state = TEGRA_UART_SUSPEND;
 	return 0;
 }
 
@@ -1142,7 +1158,11 @@ static int tegra_uart_resume(struct platform_device *pdev)
 	dev_err(t->uport.dev, "tegra_uart_resume called\n");
 	if (t->pinmux)
 		tegra_pinmux_config_tristate_table(t->pinmux, t->nr_pins, TEGRA_TRI_NORMAL);
-	uart_resume_port(&tegra_uart_driver, u);
+
+	if (t->uart_state == TEGRA_UART_SUSPEND) {
+		uart_resume_port(&tegra_uart_driver, u);
+		t->uart_state = TEGRA_UART_OPENED;
+	}
 	return 0;
 }
 
@@ -1217,12 +1237,82 @@ static int __init tegra_uart_probe(struct platform_device *pdev)
 	pr_info("Registered UART port %s%d\n",
 		tegra_uart_driver.dev_name, u->line);
 
+	t->uart_state = TEGRA_UART_CLOSED;
 	return ret;
 fail:
 	kfree(t);
 	return -ENODEV;
 }
 
+/* Switch off the clock of the uart controller. */
+void tegra_uart_request_clock_off(struct uart_port *uport)
+{
+	unsigned long flags;
+	struct tegra_uart_port *t;
+
+	dev_vdbg(uport->dev, "tegra_uart_request_clock_off");
+
+	t = container_of(uport, struct tegra_uart_port, uport);
+	spin_lock_irqsave(&uport->lock, flags);
+	if (t->uart_state == TEGRA_UART_OPENED) {
+		clk_disable(t->clk);
+		t->uart_state = TEGRA_UART_CLOCK_OFF;
+	}
+	spin_unlock_irqrestore(&uport->lock, flags);
+	return;
+}
+
+/* Switch on the clock of the uart controller */
+void tegra_uart_request_clock_on(struct uart_port *uport)
+{
+	unsigned long flags;
+	struct tegra_uart_port *t;
+
+	t = container_of(uport, struct tegra_uart_port, uport);
+	spin_lock_irqsave(&uport->lock, flags);
+	if (t->uart_state == TEGRA_UART_CLOCK_OFF) {
+		clk_enable(t->clk);
+		t->uart_state = TEGRA_UART_OPENED;
+	}
+	spin_unlock_irqrestore(&uport->lock, flags);
+	return;
+}
+
+/* Set the modem control signals state of uart controller. */
+void tegra_uart_set_mctrl(struct uart_port *uport, unsigned int mctrl)
+{
+	unsigned long flags;
+	unsigned char mcr;
+	struct tegra_uart_port *t;
+
+	t = container_of(uport, struct tegra_uart_port, uport);
+	spin_lock_irqsave(&uport->lock, flags);
+	mcr = t->mcr_shadow;
+	if (mctrl & TIOCM_RTS) {
+		t->rts_active = true;
+		set_rts(t, true);
+	} else {
+		t->rts_active = false;
+		set_rts(t, false);
+	}
+
+	if (mctrl & TIOCM_DTR)
+		set_dtr(t, true);
+	else
+		set_dtr(t, false);
+	spin_unlock_irqrestore(&uport->lock, flags);
+	return;
+}
+
+/* Return the status of the transmit fifo whether empty or not.
+ * Return 0 if tx fifo is not empty.
+ * Return TIOCSER_TEMT if tx fifo is empty.
+ */
+int tegra_uart_is_tx_empty(struct uart_port *uport)
+{
+	return tegra_tx_empty(uport);
+}
+
 static int __init tegra_uart_init(void)
 {
 	int ret;