Linux I2C development

* Re: [PATCH v2] i2c: designware: add reset interface
From: zhangfei @ 2016-12-16  3:01 UTC (permalink / raw)
  To: Ramiro Oliveira, Andy Shevchenko, Wolfram Sang,
	mika.westerberg@linux.intel.com, jarkko.nikula@linux.intel.com,
	Philipp Zabel
  Cc: linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org
In-Reply-To: <fd0afd5f-6ee4-a06f-2d03-444f71662c1b@linaro.org>

Hi, Philipp

On 2016年12月16日 10:45, zhangfei wrote:
>
>
> On 2016年12月15日 23:30, Ramiro Oliveira wrote:
>> Hi Andy and Zhangfei
>>
>> On 12/15/2016 12:33 PM, Andy Shevchenko wrote:
>>> On Thu, 2016-12-15 at 16:59 +0800, Zhangfei Gao wrote:
>>>> Some platforms like hi3660 need do reset first to allow accessing
>>>> registers
>>> Patch itself looks good, but would be nice to have it tested.
>>>
>>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>
>> I tested the patch and it's working for the ARC architecture.
>>
>>>> Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
>>>> ---
>>>>   drivers/i2c/busses/i2c-designware-core.h    |  1 +
>>>>   drivers/i2c/busses/i2c-designware-platdrv.c | 28
>>>> ++++++++++++++++++++++++----
>>>>   2 files changed, 25 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-designware-core.h
>>>> b/drivers/i2c/busses/i2c-designware-core.h
>>>> index 0d44d2a..94b14fa 100644
>>>> --- a/drivers/i2c/busses/i2c-designware-core.h
>>>> +++ b/drivers/i2c/busses/i2c-designware-core.h
>>>> @@ -80,6 +80,7 @@ struct dw_i2c_dev {
>>>>       void __iomem        *base;
>>>>       struct completion    cmd_complete;
>>>>       struct clk        *clk;
>>>> +    struct reset_control    *rst;
>>>>       u32            (*get_clk_rate_khz) (struct
>>>> dw_i2c_dev *dev);
>>>>       struct dw_pci_controller *controller;
>>>>       int            cmd_err;
>>>> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c
>>>> b/drivers/i2c/busses/i2c-designware-platdrv.c
>>>> index 0b42a12..e9016ae 100644
>>>> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
>>>> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
>>>> @@ -38,6 +38,7 @@
>>>>   #include <linux/pm_runtime.h>
>>>>   #include <linux/property.h>
>>>>   #include <linux/io.h>
>>>> +#include <linux/reset.h>
>>>>   #include <linux/slab.h>
>>>>   #include <linux/acpi.h>
>>>>   #include <linux/platform_data/i2c-designware.h>
>>>> @@ -176,6 +177,14 @@ static int dw_i2c_plat_probe(struct
>>>> platform_device *pdev)
>>>>       dev->irq = irq;
>>>>       platform_set_drvdata(pdev, dev);
>>>>   +    dev->rst = devm_reset_control_get_optional(&pdev->dev, NULL);
>> devm_reset_control_get_optional() is deprecated as explained in 
>> linux/reset.h,
>> you should use devm_reset_control_get_optional_exclusive() or
>> devm_reset_control_get_optional_shared() instead, as applicable.
>>
>> I submitted a similar patch earlier today and I made the same mistake.
>
> Thanks Ramiro for the info
> Will use devm_reset_control_get_optional_exclusive instead.
> But should the interface be as simple as possible?
>
> Thanks
Sorry, a bit confused.
Is that mean we should not use devm_reset_control_get_optional()
While driver should decide whether use 
devm_reset_control_get_optional_exclusive() or
devm_reset_control_get_optional_shared()
What if different platform has different requirement?

Looks the difference between _exclusive and _shared is refcount,
How about handle this inside, and not decided by interface?

Thanks

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