On DA850/OMAP-L138 SoC, the PLL which supplies the clock to CPU also feeds the UART and the UART input frequency can change when the CPU frequency is scaled.
This patch adds cpufreq support for 8250 serial driver. A clk structure member has been added to the platform and port data structure. This member is used by the cpufreq notifier callback to get the updated clock rate. The implementation is based on the cpufreq implementation for Samsung serial driver. This implementation has been tested on TI DA850/OMAP-L138 EVM. Signed-off-by: Chaithrika U S <[email protected]> --- This patch is posted here for review and will be posted to LKML later. drivers/serial/8250.c | 81 +++++++++++++++++++++++++++++++++++++++++++ include/linux/serial_8250.h | 1 + 2 files changed, 82 insertions(+), 0 deletions(-) diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index c3e37c8..612e129 100644 --- a/drivers/serial/8250.c +++ b/drivers/serial/8250.c @@ -38,6 +38,8 @@ #include <linux/serial_8250.h> #include <linux/nmi.h> #include <linux/mutex.h> +#include <linux/cpufreq.h> +#include <linux/clk.h> #include <asm/io.h> #include <asm/irq.h> @@ -156,6 +158,10 @@ struct uart_8250_port { */ void (*pm)(struct uart_port *port, unsigned int state, unsigned int old); + struct clk *uart_clk; +#ifdef CONFIG_CPU_FREQ + struct notifier_block freq_transition; +#endif }; struct irq_info { @@ -2931,6 +2937,70 @@ void serial8250_resume_port(int line) uart_resume_port(&serial8250_reg, &up->port); } +#ifdef CONFIG_CPU_FREQ +static int serial8250_cpufreq_transition(struct notifier_block *nb, + unsigned long val, void *data) +{ + struct uart_8250_port *p; + struct uart_port *uport; + + p = container_of(nb, struct uart_8250_port, freq_transition); + uport = &p->port; + + if(!p->port.uartclk) + goto cpu_freq_exit; + + if (p->port.uartclk == clk_get_rate(p->uart_clk)) + goto cpu_freq_exit; + + p->port.uartclk = clk_get_rate(p->uart_clk); + if (val == CPUFREQ_POSTCHANGE) { + struct ktermios *termios; + struct tty_struct *tty; + if (uport->state == NULL) + goto cpu_freq_exit; + + tty = uport->state->port.tty; + if (tty == NULL) + goto cpu_freq_exit; + + termios = tty->termios; + if (termios == NULL) { + printk(KERN_WARNING "%s: no termios?\n", __func__); + goto cpu_freq_exit; + } + + serial8250_set_termios(uport, termios, NULL); + } + +cpu_freq_exit: + return 0; +} + +static inline int serial8250_cpufreq_register(struct uart_8250_port *p) +{ + p->freq_transition.notifier_call = serial8250_cpufreq_transition; + + return cpufreq_register_notifier(&p->freq_transition, + CPUFREQ_TRANSITION_NOTIFIER); +} + +static inline void serial8250_cpufreq_deregister(struct uart_8250_port *p) +{ + cpufreq_unregister_notifier(&p->freq_transition, + CPUFREQ_TRANSITION_NOTIFIER); +} +#else +static inline int serial8250_cpufreq_register(struct uart_8250_port *p) +{ + return 0; +} + +static inline void serial8250_cpufreq_deregister(struct uart_8250_port *p) +{ +} +#endif + /* * Register a set of serial devices attached to a platform device. The * list is terminated with a zero flags entry, which means we expect @@ -3090,6 +3160,7 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port * */ int serial8250_register_port(struct uart_port *port) { + struct plat_serial8250_port *p; struct uart_8250_port *uart; int ret = -ENOSPC; @@ -3116,6 +3187,10 @@ int serial8250_register_port(struct uart_port *port) if (port->dev) uart->port.dev = port->dev; + p = port->dev->platform_data; + if (p->uart_clk) + uart->uart_clk = p->uart_clk; + if (port->flags & UPF_FIXED_TYPE) { uart->port.type = port->type; uart->port.fifosize = uart_config[port->type].fifo_size; @@ -3133,6 +3208,11 @@ int serial8250_register_port(struct uart_port *port) ret = uart_add_one_port(&serial8250_reg, &uart->port); if (ret == 0) ret = uart->port.line; + + ret = serial8250_cpufreq_register(uart); + if (ret < 0) + printk(KERN_ERR "Failed to add cpufreq notifier\n"); + } mutex_unlock(&serial_mutex); @@ -3152,6 +3232,7 @@ void serial8250_unregister_port(int line) struct uart_8250_port *uart = &serial8250_ports[line]; mutex_lock(&serial_mutex); + serial8250_cpufreq_deregister(uart); uart_remove_one_port(&serial8250_reg, &uart->port); if (serial8250_isa_devs) { uart->port.flags &= ~UPF_BOOT_AUTOCONF; diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index fb46aba..d85201f 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -23,6 +23,7 @@ struct plat_serial8250_port { resource_size_t mapbase; /* resource base */ unsigned int irq; /* interrupt number */ unsigned long irqflags; /* request_irq flags */ + struct clk *uart_clk; unsigned int uartclk; /* UART clock rate */ void *private_data; unsigned char regshift; /* register shift */ -- 1.5.6 _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
