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From: Philippe Langlais on 19 Jul 2010 05:30
UART Features extract from STEricsson U6715 datasheet (arm926 SoC for mobile phone):
* Fully compatible with industry standard 16C550 and 16C450 from various
manufacturers
* RX and TX 64 byte FIFO reduces CPU interrupts
* Full double buffering
* Modem control signals include CTS, RTS, (and DSR, DTR on UART1 only)
* Automatic baud rate selection
* Manual or automatic RTS/CTS smart hardware flow control
* Programmable serial characteristics:
– Baud rate generation (50 to 3.25M baud)
– 5, 6, 7 or 8-bit characters
– Even, odd or no-parity bit generation and detection
– 1, 1.5 or 2 stop bit generation
* Independent control of transmit, receive, line status, data set interrupts and FIFOs
* Full status-reporting capabilities
* Separate DMA signalling for RX and TX
* Timed interrupt to spread receive interrupt on known duration
* DMA time-out interrupt to allow detection of end of reception
* Carkit pulse coding and decoding compliant with USB carkit control interface [40]

This UART IP is auto-detected as a 16550A type

Clock specificities:
It's parent clock depend on baud rate.
The UART port can be used before u6xxx clock framework initialization

Signed-off-by: Philippe Langlais <philippe.langlais(a)stericsson.com>
---
drivers/serial/8250.c | 26 ++++++-
drivers/serial/8250_u6.c | 179 +++++++++++++++++++++++++++++++++++++++++++
drivers/serial/Kconfig | 19 +++++
drivers/serial/Makefile | 1 +
include/linux/serial_8250.h | 8 ++
5 files changed, 232 insertions(+), 1 deletions(-)
create mode 100644 drivers/serial/8250_u6.c

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 607ed7f..269950f 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -199,10 +199,16 @@ static const struct serial8250_config uart_config[] = {
},
[PORT_16550A] = {
.name = "16550A",
+#if defined(CONFIG_SERIAL_8250_U6XXX)
+ .fifo_size = 64,
+ .tx_loadsz = 64,
+ .flags = UART_CAP_FIFO | UART_CAP_AFE,
+#else
.fifo_size = 16,
.tx_loadsz = 16,
- .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
.flags = UART_CAP_FIFO,
+#endif
+ .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
},
[PORT_CIRRUS] = {
.name = "Cirrus",
@@ -2268,6 +2274,13 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
/*
* Ask the core to calculate the divisor for us.
*/
+#ifdef CONFIG_SERIAL_8250_CUSTOM_CLOCK
+ baud = uart_get_baud_rate(port, termios, old, 0,
+ CONFIG_SERIAL_8250_CUSTOM_MAX_BAUDRATE);
+ /* Calculate the new uart clock frequency if it is tunable */
+ port->uartclk = serial8250_get_custom_clock(port, baud);
+#endif
+
baud = uart_get_baud_rate(port, termios, old,
port->uartclk / 16 / 0xffff,
port->uartclk / 16);
@@ -2298,6 +2311,13 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
up->mcr &= ~UART_MCR_AFE;
if (termios->c_cflag & CRTSCTS)
up->mcr |= UART_MCR_AFE;
+#if defined(CONFIG_SERIAL_8250_U6XXX)
+ /**
+ * When AFE is active, let the HW handle the stop/restart TX
+ * upon CTS change. It reacts much quicker than the SW driver.
+ */
+ port->flags &= ~ASYNC_CTS_FLOW;
+#endif
}

/*
@@ -2383,6 +2403,10 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
serial_outp(up, UART_LCR, cval | UART_LCR_DLAB);/* set DLAB */
}

+#ifdef CONFIG_SERIAL_8250_CUSTOM_CLOCK
+ /* set the new uart clock frequency if it is tunable */
+ serial8250_set_custom_clock(port);
+#endif
serial_dl_write(up, quot);

/*
diff --git a/drivers/serial/8250_u6.c b/drivers/serial/8250_u6.c
new file mode 100644
index 0000000..bcc0f98
--- /dev/null
+++ b/drivers/serial/8250_u6.c
@@ -0,0 +1,179 @@
+/*
+ * linux/drivers/serial/8250_pnx.c
+ *
+ * Copyright (C) ST-Ericsson SA 2010
+ * Author: Ludovic Barre <ludovic.barre(a)stericsson.com> for ST-Ericsson.
+ * License terms: GNU General Public License (GPL), version 2
+ */
+
+#include <linux/serial_core.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+
+#include <mach/serial.h>
+#include <mach/hardware.h>
+#include <mach/clock.h>
+
+/* Register description for FDIV_CTRL */
+/* UART FDIV_CTRL Register (8 bits) */
+#define UARTX_FDIV_CTRL_OFFSET 0xC00
+/* UART FDIV_M Register (16 bits) */
+#define UARTX_FDIV_M_OFFSET 0xC04
+/* UART FDIV_N Register (16 bits) */
+#define UARTX_FDIV_N_OFFSET 0xC08
+
+/* Bits definition for register UARTX_FDIV_CTRL */
+#define UARTX_FDIV_ENABLE_SHIFT 7
+#define UARTX_FDIV_ENABLE_FIELD (0xFFFFFFFF - (0x1UL<<UARTX_FDIV_ENABLE_SHIFT))
+#define UARTX_FDIV_ENABLE_OFF (0x0UL<<UARTX_FDIV_ENABLE_SHIFT)
+#define UARTX_FDIV_ENABLE_ON (0x1UL<<UARTX_FDIV_ENABLE_SHIFT)
+#define UARTX_FDIV_ENABLE (0x1UL<<UARTX_FDIV_ENABLE_SHIFT)
+#define UARTX_CLKSEL_SHIFT 0
+#define UARTX_CLKSEL_FIELD (0xFFFFFFFF - (0x3UL<<UARTX_CLKSEL_SHIFT))
+#define UARTX_CLKSEL_PCLK (0x0UL<<UARTX_CLKSEL_SHIFT)
+#define UARTX_CLKSEL_13M (0x1UL<<UARTX_CLKSEL_SHIFT)
+#define UARTX_CLKSEL_26M (0x2UL<<UARTX_CLKSEL_SHIFT)
+#define UARTX_CLKSEL_3 (0x3UL<<UARTX_CLKSEL_SHIFT)
+
+/*
+ * console and pctools has needed to start before serial_init
+ * (with cgu interface)
+ */
+static int uart_enable_clock(struct uart_port *port)
+{
+ u32 v;
+ v = readl(CGU_GATESC1_REG);
+
+ if (port->irq == IRQ_UART1)
+ v |= CGU_UART1EN_1;
+ else if (port->irq == IRQ_UART2)
+ v |= CGU_UART2EN_1;
+
+ writel(v, CGU_GATESC1_REG);
+
+ return 0;
+}
+
+static int uart_disable_clock(struct uart_port *port)
+{
+ u32 v;
+ v = readl(CGU_GATESC1_REG);
+
+ if (port->irq == IRQ_UART1)
+ v &= ~CGU_UART1EN_0;
+ else if (port->irq == IRQ_UART2)
+ v &= ~CGU_UART2EN_0;
+
+ writel(v, CGU_GATESC1_REG);
+
+ return 0;
+}
+
+unsigned int serial8250_enable_clock(struct uart_port *port)
+{
+ struct u6_uart *uart_u6 = port->private_data;
+
+ if (!uart_u6)
+ return uart_enable_clock(port);
+
+ if (IS_ERR(uart_u6->uartClk)) {
+ printk(KERN_WARNING "%s - uart clock failed error:%ld\n",
+ __func__, PTR_ERR(uart_u6->uartClk));
+ return PTR_ERR(uart_u6->uartClk);
+ }
+
+ if (clk_get_usecount(uart_u6->uartClk) == 0)
+ clk_enable(uart_u6->uartClk);
+ return 0;
+}
+
+unsigned int serial8250_disable_clock(struct uart_port *port)
+{
+ struct u6_uart *uart_u6 = port->private_data;
+
+ if (!uart_u6)
+ return uart_disable_clock(port);
+
+ if (IS_ERR(uart_u6->uartClk)) {
+ printk(KERN_WARNING "%s - uart clk error :%ld\n", __func__,
+ PTR_ERR(uart_u6->uartClk));
+ return PTR_ERR(uart_u6->uartClk);
+ }
+ if (clk_get_usecount(uart_u6->uartClk) >= 1)
+ clk_disable(uart_u6->uartClk);
+
+ return 0;
+}
+
+unsigned int serial8250_get_custom_clock(struct uart_port *port,
+ unsigned int baud)
+{
+ switch (baud) {
+ case 3250000:
+ return 52000000;
+ case 2000000:
+ return 32000000;
+ case 1843200:
+ return 29491200;
+ case 921600:
+ return 14745600;
+ default:
+ return 7372800;
+ }
+}
+
+void serial8250_set_custom_clock(struct uart_port *port)
+{
+ u32 fdiv_m = 0x5F37;
+ u32 fdiv_n = 0x3600;
+ u32 fdiv_ctrl = UARTX_FDIV_ENABLE_ON;
+ struct u6_uart *uart_u6 = port->private_data;
+
+ switch (port->uartclk) {
+ case 7372800: /* clk=13MHz */
+ fdiv_ctrl |= UARTX_CLKSEL_13M;
+ break;
+ case 14745600: /* clk=26MHz */
+ fdiv_ctrl |= UARTX_CLKSEL_26M;
+ break;
+ case 29491200: /* clk=pclk */
+ fdiv_ctrl |= UARTX_CLKSEL_PCLK;
+ break;
+ case 32000000: /* clk=pclk */
+ fdiv_n = 0x3A98;
+ fdiv_ctrl |= UARTX_CLKSEL_PCLK;
+ break;
+ case 52000000: /* clk=pclk */
+ fdiv_n = 0x5F37;
+ fdiv_ctrl |= UARTX_CLKSEL_PCLK;
+ break;
+ }
+
+ if (uart_u6 != NULL && !IS_ERR(uart_u6->uartClk)) {
+ /* if cgu interface is ready and u6_serial_init */
+ struct clk *parentClk;
+
+ if (fdiv_ctrl & UARTX_CLKSEL_26M)
+ parentClk = clk_get(NULL, "clk26m_ck");
+ else if (fdiv_ctrl & UARTX_CLKSEL_PCLK)
+ parentClk = clk_get(NULL, "pclk2_ck");
+ else
+ parentClk = clk_get(NULL, "clk13m_ck");
+
+ if (!IS_ERR(parentClk)) {
+ serial8250_disable_clock(port);
+
+ if (clk_set_parent(uart_u6->uartClk, parentClk) != 0)
+ printk(KERN_WARNING "%s: set parent failed\n", __func__);
+
+ serial8250_enable_clock(port);
+ clk_put(parentClk);
+ }
+ }
+
+ writel(fdiv_m, port->membase + UARTX_FDIV_M_OFFSET);
+ writel(fdiv_n, port->membase + UARTX_FDIV_N_OFFSET);
+ writel(fdiv_ctrl, port->membase + UARTX_FDIV_CTRL_OFFSET);
+}
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 45ad290..ce93eae 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -163,6 +163,25 @@ config SERIAL_8250_MANY_PORTS
say N here to save some memory. You can also say Y if you have an
"intelligent" multiport card such as Cyclades, Digiboards, etc.

+config SERIAL_8250_U6XXX
+ bool
+ depends on SERIAL_8250_EXTENDED && PLAT_U6XXX
+ default y
+
+config SERIAL_8250_CUSTOM_CLOCK
+ bool "Support serial ports with tunable input clock frequency"
+ depends on SERIAL_8250_EXTENDED && SERIAL_8250_U6XXX
+ default y
+ help
+ Say Y here if your platform has specific registers to change UART clock frequency.
+
+config SERIAL_8250_CUSTOM_MAX_BAUDRATE
+ int "Maximal reachable baudrate"
+ depends on SERIAL_8250_CUSTOM_CLOCK
+ default "3250000"
+ help
+ The value of the maximal reachable baudrate when tuning UART clock frequency (default value: 3.25MBds).
+
#
# Multi-port serial cards
#
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index a5edb49..dca7c9a 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SERIAL_8250_BOCA) += 8250_boca.o
obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554) += 8250_exar_st16c554.o
obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o
obj-$(CONFIG_SERIAL_8250_MCA) += 8250_mca.o
+obj-$(CONFIG_SERIAL_8250_U6XXX) += 8250_u6.o
obj-$(CONFIG_SERIAL_AMBA_PL010) += amba-pl010.o
obj-$(CONFIG_SERIAL_AMBA_PL011) += amba-pl011.o
obj-$(CONFIG_SERIAL_CLPS711X) += clps711x.o
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index fb46aba..3e86ceb 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -72,4 +72,12 @@ extern int serial8250_find_port(struct uart_port *p);
extern int serial8250_find_port_for_earlycon(void);
extern int setup_early_serial8250_console(char *cmdline);

+#ifdef CONFIG_SERIAL_8250_CUSTOM_CLOCK
+unsigned int serial8250_enable_clock(struct uart_port *port);
+unsigned int serial8250_disable_clock(struct uart_port *port);
+unsigned int serial8250_get_custom_clock(struct uart_port *port,
+ unsigned int baud);
+void serial8250_set_custom_clock(struct uart_port *port);
+#endif
+
#endif
--
1.7.1

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Prev: trivial: fix typos concerning "challenge"
Next: [PATCH] usb: gadget: functionfs: stale Makefile entry removed