linux-kernel - Re: [PATCH 1/2] i2c: omap: convert to module_platform

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Date:	Tue, 04 Jun 2013 11:29:34 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	"Ben Dooks \(embedded platforms\)" <ben-linux@...ff.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	<linux-omap@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] i2c: omap: convert to module_platform_driver()

Grygorii Strashko <grygorii.strashko@...com> writes:

> Hi Kevin,
> On 06/03/2013 11:59 PM, Kevin Hilman wrote:
>> Grygorii Strashko <grygorii.strashko@...com> writes:
>>
>>> The OMAP I2C driver has a relation to pinctrl-single driver. As result,
>>> its probe will be deferred during system boot until late init time,
>>> because the pinctrl-single is initizalized as moudle/device init time.
>>> This, in turn, will delay initialization of all I2C devices (like mfd,
>>> I2C regulators and etc.) and cause boot delay (more over, it can broken
>>> initialization of drivers which are not ready to use deferred probe
>>> mechanism yet, for example DSS).
>>>
>>> There are no sense to keep OMAP I2C initialization on subsys init layer
>>> any more, hence shift it to module/device layer where the i2c <-->
>>> pinctrl-single dependency is resolved in drivers/Makefile now.
>>>
>>> Cc: Wolfram Sang <wsa@...-dreams.de>
>>> Cc: "Ben Dooks (embedded platforms)" <ben-linux@...ff.org>
>>> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
>>> Cc: linux-omap@...r.kernel.org
>>> Cc: linux-i2c@...r.kernel.org
>>> Cc: linux-kernel@...r.kernel.org
>>>
>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>> Testing this patch with PATCH 1/2, the twl_rtc driver fails to correctly
>> initialize on OMAP3:
>>
>>           twl_rtc rtc.22: hctosys: invalid date/time
>>
>> instead of the expected result:
>>
>>            twl_rtc rtc.22: setting system clock to 2000-01-01 00:00:00 UTC (946684800)
>>
>> so something is still not right for the init sequence.
>>
>> Kevin
> I think, the root cause of the problem isn't this patch - it's just
> yet another side effect
> of using deferred probes :). I've taken a look on twl-rtc code and
> found possible error place
> static int __init twl_rtc_init(void)
> {
>     if (twl_class_is_4030()) <------ here,
>         rtc_reg_map = (u8 *) twl4030_rtc_reg_map;
>     else
>         rtc_reg_map = (u8 *) twl6030_rtc_reg_map;
>
>     return platform_driver_register(&twl4030rtc_driver);
> }
> In drivers/Makefile:
> obj-$(CONFIG_RTC_LIB)        += rtc/  <------ RTC is placed before I2C
> obj-y                += i2c/ media/ <----- and only here I2C bus
> instantiates TWL-core device
> and configures twl_priv->twl_id
>
> Thats why it's working on my OMAP4/twl6030 board. Could you check if
> below fix will work on OMAP3:

Yes, your fix works.  Thanks for digging into it.

Care to send a proper patch?  Please be sure to send to Andrew Morton
also, since he'll be the one to queue the RTC patch.

> diff --git a/drivers/rtc/rtc-twl.c b/drivers/rtc/rtc-twl.c
> index 8751a52..aaa5015 100644
> --- a/drivers/rtc/rtc-twl.c
> +++ b/drivers/rtc/rtc-twl.c
> @@ -469,6 +469,11 @@ static int twl_rtc_probe(struct platform_device *pdev)
>         if (irq <= 0)
>                 goto out1;
>
> +       if (twl_class_is_4030())
> +               rtc_reg_map = (u8 *) twl4030_rtc_reg_map;
> +       else
> +               rtc_reg_map = (u8 *) twl6030_rtc_reg_map;
> +
>         ret = twl_rtc_read_u8(&rd_reg, REG_RTC_STATUS_REG);
>         if (ret < 0)
>                 goto out1;
> @@ -610,11 +615,6 @@ static struct platform_driver twl4030rtc_driver = {
>
>  static int __init twl_rtc_init(void)
>  {
> -       if (twl_class_is_4030())
> -               rtc_reg_map = (u8 *) twl4030_rtc_reg_map;
> -       else
> -               rtc_reg_map = (u8 *) twl6030_rtc_reg_map;
> -
>         return platform_driver_register(&twl4030rtc_driver);
>  }
>  module_init(twl_rtc_init);
>
> Unfortunately, I have no OMAP3 HW and can't check it.

I suggest you find a Beagle or Gumstix/Overo type board someplace.
There is an abundance of cheap OMAP3 hardware available.

Kevin

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