[i2c] [PATCH 1/1] Blackfin I2C Driver: Functional power management support

[Hennerich, Michael]

>From: Ben Dooks [mailto:ben-linux at fluff.org]
>
>On Mon, Jul 28, 2008 at 06:07:28PM +0800, Bryan Wu wrote:
>> On Mon, Jul 28, 2008 at 5:23 PM, Ben Dooks <ben-linux at fluff.org>
wrote:
>> > On Sun, Jul 27, 2008 at 02:41:54PM +0800, Bryan Wu wrote:
>> >> From: Michael Hennerich <michael.hennerich at analog.com>
>> >>
>> >> PM_SUSPEND_MEM: Blackfin does not maintain register state through
>> >> Hibernate. Save and restore peripheral base initialization during
>> >> PM transitions.
>> >>
>> >> Signed-off-by: Michael Hennerich <michael.hennerich at analog.com>
>> >> Signed-off-by: Bryan Wu <cooloney at kernel.org>
>> >> ---
>> >>  drivers/i2c/busses/i2c-bfin-twi.c |   35
++++++++++++++++++++++++----
>-------
>> >>  1 files changed, 24 insertions(+), 11 deletions(-)
>> >>
>> >> diff --git a/drivers/i2c/busses/i2c-bfin-twi.c
>b/drivers/i2c/busses/i2c-bfin-twi.c
>> >> index 48d084b..3c855ff 100644
>> >> --- a/drivers/i2c/busses/i2c-bfin-twi.c
>> >> +++ b/drivers/i2c/busses/i2c-bfin-twi.c
>> >> @@ -49,6 +49,8 @@ struct bfin_twi_iface {
>> >>       struct i2c_msg          *pmsg;
>> >>       int                     msg_num;
>> >>       int                     cur_msg;
>> >> +     u16                     saved_clkdiv;
>> >> +     u16                     saved_control;
>> >>       void __iomem            *regs_base;
>> >>  };
>> >>
>> >> @@ -565,32 +567,43 @@ static u32 bfin_twi_functionality(struct
>i2c_adapter *adap)
>> >>              I2C_FUNC_I2C;
>> >>  }
>> >>
>> >> -
>> >>  static struct i2c_algorithm bfin_twi_algorithm = {
>> >>       .master_xfer   = bfin_twi_master_xfer,
>> >>       .smbus_xfer    = bfin_twi_smbus_xfer,
>> >>       .functionality = bfin_twi_functionality,
>> >>  };
>> >>
>> >> -
>> >> -static int i2c_bfin_twi_suspend(struct platform_device *dev,
>pm_message_t state)
>> >> +static int i2c_bfin_twi_suspend(struct platform_device *pdev,
>pm_message_t state)
>> >>  {
>> >> -     struct bfin_twi_iface *iface = platform_get_drvdata(dev);
>> >> +     struct bfin_twi_iface *iface = platform_get_drvdata(pdev);
>> >> +
>> >> +     iface->saved_clkdiv = read_CLKDIV(iface);
>> >> +     iface->saved_control = read_CONTROL(iface);
>> >> +
>> >> +     free_irq(iface->irq, iface);
>> >>
>> >>       /* Disable TWI */
>> >> -     write_CONTROL(iface, read_CONTROL(iface) & ~TWI_ENA);
>> >> -     SSYNC();
>> >> +     write_CONTROL(iface, iface->saved_control & ~TWI_ENA);
>> >
>> > I assume removing the SSYNC() call is valid?
>> >
>>
>> Yes, I think it is OK for that. We tested on our platform.
>> Actually, keeping the SSYNC() is not a big deal for this driver.
>> How do you think Michael?
>>
>> >>       return 0;
>> >>  }
>> >>
>> >> -static int i2c_bfin_twi_resume(struct platform_device *dev)
>> >> +static int i2c_bfin_twi_resume(struct platform_device *pdev)
>> >>  {
>> >> -     struct bfin_twi_iface *iface = platform_get_drvdata(dev);
>> >> +     struct bfin_twi_iface *iface = platform_get_drvdata(pdev);
>> >>
>> >> -     /* Enable TWI */
>> >> -     write_CONTROL(iface, read_CONTROL(iface) | TWI_ENA);
>> >> -     SSYNC();
>> >> +     int rc = request_irq(iface->irq, bfin_twi_interrupt_entry,
>> >> +             IRQF_DISABLED, pdev->name, iface);
>> >> +     if (rc) {
>> >> +             dev_err(&pdev->dev, "Can't get IRQ %d !\n",
iface->irq);
>> >> +             return -ENODEV;
>> >> +     }
>> >> +
>> >> +     /* Resume TWI interface clock as specified */
>> >> +     write_CLKDIV(iface, iface->saved_clkdiv);
>> >> +
>> >> +     /* Resume TWI */
>> >> +     write_CONTROL(iface, iface->saved_control);
>> >>
>> >>       return 0;
>> >>  }
>> >> --
>> >> 1.5.6
>> >
>> > if removing the SSYNC() call is ok, then I'll queue this into
>> > my tree which I will be requesting a pull asap.
>
>ok, this is in my queue, unless anyone objects then it'll be pushed
>out later today.

Removing this SSYNC is absolutely safe. There are potentially many other
ones that can be removed too.

Michael

>
>--
>Ben
>
>Q:      What's a light-year?
>A:      One-third less calories than a regular year.