Re: [PATCH 1/2] i2c: omap: convert to module_platform_driver()

From: Grygorii Strashko
Date: Tue Jun 04 2013 - 07:36:45 EST

Hi Kevin,
On 06/03/2013 11:59 PM, Kevin Hilman wrote:
Grygorii Strashko <grygorii.strashko@xxxxxx> 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@xxxxxxxxxxxxx>
Cc: "Ben Dooks (embedded platforms)" <ben-linux@xxxxxxxxx>
Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
Cc: linux-omap@xxxxxxxxxxxxxxx
Cc: linux-i2c@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
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.

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;
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:
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);

Unfortunately, I have no OMAP3 HW and can't check it.


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