8250 serial driver and PM

8250 serial driver and PM

[Grigory Tolstolytkin]

Hi,

I'm working on power management support for a particular ARM based board 
and I've got a question:
I want to add a board specific power management for standard uart driver 
(serial8250). For this purpose there is a special hook defined in 
uart_8250_port structure (drivers/serial/8250.c):
...
 >        /*
 >        * We provide a per-port pm hook.
 >         */
 >        void                    (*pm)(struct uart_port *port,
 >                                      unsigned int state, unsigned int 
old);
...

When driver goes into suspend/resume, serial8250_pm() function is called 
and it checks for the hook and executes it if it exists. But I didn't 
find a proper way to assign my own function to this hook.
How this hook is supposed to be changed? Is there a way to correctly 
initialize it and how it should be done?
Whether it's a good way to initialize it, for example, in 
serial8250_isa_init_ports():
...
                up->mcr_mask = ~ALPHA_KLUDGE_MCR;
                up->mcr_force = ALPHA_KLUDGE_MCR;

                up->port.ops = &serial8250_pops;

#ifdef CONFIG_ARCH_XXX
                up->pm = pnx4008_uart_pm;
#endif
       }
...

Or it's a bad manner?

Any help appreciated,

Thanks,
Grigory.

Re: 8250 serial driver and PM

[Russell King]

On Mon, Aug 29, 2005 at 09:55:04PM +0400, Grigory Tolstolytkin wrote:
> I'm working on power management support for a particular ARM based board 
> and I've got a question:
> I want to add a board specific power management for standard uart driver 
> (serial8250). For this purpose there is a special hook defined in 
> uart_8250_port structure (drivers/serial/8250.c):
> ...
>  >        /*
>  >        * We provide a per-port pm hook.
>  >         */
>  >        void                    (*pm)(struct uart_port *port,
>  >                                      unsigned int state, unsigned int 
> old);
> ...
> 
> When driver goes into suspend/resume, serial8250_pm() function is called 
> and it checks for the hook and executes it if it exists. But I didn't 
> find a proper way to assign my own function to this hook.

We probably want to pass it via the platform device - which probably
means changing that interface.

> How this hook is supposed to be changed?

It's something which wasn't thought about since there were very few
people wanting to use it, and further work needed to be done (as my
first comment) to allow it to be used - which basically meant changing
the initialisation paths to allow platform devices (now done).

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core

Re: 8250 serial driver and PM

[Vitaly Wool]

Hi Grigory,
it's unclear from your letter where you take pnx4008_uart_pm from. Can 
you please elaborate?

What I would think of if I were you is adding a field 'pm' to struct 
plat_serial8250_port which is filled in in the architecture-specific 
part and setting up->pm accrodingly.
I'll send a patch that may be of a help for you shortly.

Best regards,
   Vitaly


Grigory Tolstolytkin wrote:

> Hi,
>
> I'm working on power management support for a particular ARM based 
> board and I've got a question:
> I want to add a board specific power management for standard uart 
> driver (serial8250). For this purpose there is a special hook defined 
> in uart_8250_port structure (drivers/serial/8250.c):
> ...
> >        /*
> >        * We provide a per-port pm hook.
> >         */
> >        void                    (*pm)(struct uart_port *port,
> >                                      unsigned int state, unsigned 
> int old);
> ...
>
> When driver goes into suspend/resume, serial8250_pm() function is 
> called and it checks for the hook and executes it if it exists. But I 
> didn't find a proper way to assign my own function to this hook.
> How this hook is supposed to be changed? Is there a way to correctly 
> initialize it and how it should be done?
> Whether it's a good way to initialize it, for example, in 
> serial8250_isa_init_ports():
> ...
>                up->mcr_mask = ~ALPHA_KLUDGE_MCR;
>                up->mcr_force = ALPHA_KLUDGE_MCR;
>
>                up->port.ops = &serial8250_pops;
>
> #ifdef CONFIG_ARCH_XXX
>                up->pm = pnx4008_uart_pm;
> #endif
>       }
> ...
>
> Or it's a bad manner?
>
> Any help appreciated,
>
> Thanks,
> Grigory.
>
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