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Date: Thu, 17 Oct 2013 14:08:11 -0700
From: Soren Brinkmann <soren.brinkmann@...inx.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.cz>,
Michal Simek <michal.simek@...inx.com>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
Soren Brinkmann <soren.brinkmann@...inx.com>
Subject: [PATCH 08/10] tty: xuartps: Dynamically adjust to input frequency changes
Add a clock notifier to dynamically handle frequency changes of the
input clock by reprogramming the UART in order to keep the baud rate
constant.
Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
---
drivers/tty/serial/xilinx_uartps.c | 123 +++++++++++++++++++++++++++++++++++--
1 file changed, 119 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 95e12c216984..82195040e906 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -163,13 +163,20 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
/**
* struct xuartps - device data
- * @refclk Reference clock
- * @aperclk APB clock
+ * @port Pointer to the UART port
+ * @refclk Reference clock
+ * @aperclk APB clock
+ * @baud Current baud rate
+ * @clk_rate_change_nb Notifier block for clock changes
*/
struct xuartps {
+ struct uart_port *port;
struct clk *refclk;
struct clk *aperclk;
+ unsigned int baud;
+ struct notifier_block clk_rate_change_nb;
};
+#define to_xuartps(_nb) container_of(_nb, struct xuartps, clk_rate_change_nb);
/**
* xuartps_isr - Interrupt handler
@@ -385,6 +392,7 @@ static unsigned int xuartps_set_baud_rate(struct uart_port *port,
u32 cd, bdiv;
u32 mreg;
int div8;
+ struct xuartps *xuartps = port->private_data;
calc_baud = xuartps_calc_baud_divs(port->uartclk, baud, &bdiv, &cd,
&div8);
@@ -398,10 +406,105 @@ static unsigned int xuartps_set_baud_rate(struct uart_port *port,
xuartps_writel(mreg, XUARTPS_MR_OFFSET);
xuartps_writel(cd, XUARTPS_BAUDGEN_OFFSET);
xuartps_writel(bdiv, XUARTPS_BAUDDIV_OFFSET);
+ xuartps->baud = baud;
return calc_baud;
}
+/**
+ * xuartps_clk_notitifer_cb - Clock notifier callback
+ * @nb: Notifier block
+ * @event: Notify event
+ * @data: Notifier data
+ * Returns NOTIFY_OK on success, NOTIFY_BAD on error.
+ */
+static int xuartps_clk_notifier_cb(struct notifier_block *nb,
+ unsigned long event, void *data)
+{
+ u32 ctrl_reg;
+ struct uart_port *port;
+ int locked = 0;
+ struct clk_notifier_data *ndata = data;
+ unsigned long flags = 0;
+ struct xuartps *xuartps = to_xuartps(nb);
+
+ port = xuartps->port;
+ if (port->suspended)
+ return NOTIFY_OK;
+
+ switch (event) {
+ case PRE_RATE_CHANGE:
+ {
+ u32 bdiv;
+ u32 cd;
+ int div8;
+
+ /*
+ * Find out if current baud-rate can be achieved with new clock
+ * frequency.
+ */
+ if (!xuartps_calc_baud_divs(ndata->new_rate, xuartps->baud,
+ &bdiv, &cd, &div8))
+ return NOTIFY_BAD;
+
+ spin_lock_irqsave(&xuartps->port->lock, flags);
+
+ /* Disable the TX and RX to set baud rate */
+ xuartps_writel(xuartps_readl(XUARTPS_CR_OFFSET) |
+ (XUARTPS_CR_TX_DIS | XUARTPS_CR_RX_DIS),
+ XUARTPS_CR_OFFSET);
+
+ spin_unlock_irqrestore(&xuartps->port->lock, flags);
+
+ return NOTIFY_OK;
+ }
+ case POST_RATE_CHANGE:
+ /*
+ * Set clk dividers to generate correct baud with new clock
+ * frequency.
+ */
+
+ spin_lock_irqsave(&xuartps->port->lock, flags);
+
+ locked = 1;
+ port->uartclk = ndata->new_rate;
+
+ xuartps->baud = xuartps_set_baud_rate(xuartps->port,
+ xuartps->baud);
+ /* fall through */
+ case ABORT_RATE_CHANGE:
+ if (!locked)
+ spin_lock_irqsave(&xuartps->port->lock, flags);
+
+ /* Set TX/RX Reset */
+ xuartps_writel(xuartps_readl(XUARTPS_CR_OFFSET) |
+ (XUARTPS_CR_TXRST | XUARTPS_CR_RXRST),
+ XUARTPS_CR_OFFSET);
+
+ while (xuartps_readl(XUARTPS_CR_OFFSET) &
+ (XUARTPS_CR_TXRST | XUARTPS_CR_RXRST))
+ cpu_relax();
+
+ /*
+ * Clear the RX disable and TX disable bits and then set the TX
+ * enable bit and RX enable bit to enable the transmitter and
+ * receiver.
+ */
+ xuartps_writel(rx_timeout, XUARTPS_RXTOUT_OFFSET);
+ ctrl_reg = xuartps_readl(XUARTPS_CR_OFFSET);
+ xuartps_writel(
+ (ctrl_reg & ~(XUARTPS_CR_TX_DIS | XUARTPS_CR_RX_DIS)) |
+ (XUARTPS_CR_TX_EN | XUARTPS_CR_RX_EN),
+ XUARTPS_CR_OFFSET);
+
+ spin_unlock_irqrestore(&xuartps->port->lock, flags);
+
+ return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
+}
+
/*----------------------Uart Operations---------------------------*/
/**
@@ -1164,13 +1267,19 @@ static int xuartps_probe(struct platform_device *pdev)
goto err_out_clk_disable;
}
+ xuartps_data->clk_rate_change_nb.notifier_call =
+ xuartps_clk_notifier_cb;
+ if (clk_notifier_register(xuartps_data->refclk,
+ &xuartps_data->clk_rate_change_nb))
+ dev_warn(&pdev->dev, "Unable to register clock notifier.\n");
+
/* Initialize the port structure */
port = xuartps_get_port();
if (!port) {
dev_err(&pdev->dev, "Cannot get uart_port structure\n");
rc = -ENODEV;
- goto err_out_clk_disable;
+ goto err_out_notif_unreg;
} else {
/* Register the port.
* This function also registers this device with the tty layer
@@ -1181,16 +1290,20 @@ static int xuartps_probe(struct platform_device *pdev)
port->dev = &pdev->dev;
port->uartclk = clk_get_rate(xuartps_data->refclk);
port->private_data = xuartps_data;
+ xuartps_data->port = port;
platform_set_drvdata(pdev, port);
rc = uart_add_one_port(&xuartps_uart_driver, port);
if (rc) {
dev_err(&pdev->dev,
"uart_add_one_port() failed; err=%i\n", rc);
- goto err_out_clk_disable;
+ goto err_out_notif_unreg;
}
return 0;
}
+err_out_notif_unreg:
+ clk_notifier_unregister(xuartps_data->refclk,
+ &xuartps_data->clk_rate_change_nb);
err_out_clk_disable:
clk_disable_unprepare(xuartps_data->refclk);
err_out_clk_dis_aper:
@@ -1212,6 +1325,8 @@ static int xuartps_remove(struct platform_device *pdev)
int rc;
/* Remove the xuartps port from the serial core */
+ clk_notifier_unregister(xuartps_data->refclk,
+ &xuartps_data->clk_rate_change_nb);
rc = uart_remove_one_port(&xuartps_uart_driver, port);
port->mapbase = 0;
clk_disable_unprepare(xuartps_data->refclk);
--
1.8.4.1
--
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