On Mon, Jan 11, 2010 at 21:23:48, Kevin Hilman wrote:
> Chaithrika U S <[email protected]> writes:
>
> > 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.
>
> Some minor comments/questions below. Otherwise, should be posted to
> linux-serial + LKML and Cc davinci list.
>
> Hopefully somebody (hopefully Andrew) will pick this up since the 8250 driver
> has
> been orphaned for sometime.
>
I will post this patch to linux-serial and LKML lists soon.
> Kevin
>
>
> > 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;
>
> Isn't it OK to have a zero value here if you're going to use
> clk_get_rate()? or does uartclk == 0 have a special meaning here? If
> so, should be commented.
>
This is a mistake here! The if condition should check 'uart_clk' - the
clock struct pointer. I will correct this and post the updated patch.
Thanks & Regards,
Chaithrika
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