linux-kernel - Re: [PATCH v2 0/3] Add the efuse driver on rockchip platform

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Date:	Thu, 18 Jun 2015 09:29:31 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Stefan Wahren <stefan.wahren@...e.com>
CC:	Caesar Wang <wxt@...k-chips.com>, heiko@...ech.de,
	mark.rutland@....com, devicetree@...r.kernel.org,
	linux@....linux.org.uk, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, linus.walleij@...aro.org,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	robh+dt@...nel.org, galak@...eaurora.org, matthias.bgg@...il.com,
	jay.xu@...k-chips.com, linux-arm-kernel@...ts.infradead.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH v2 0/3] Add the efuse driver on rockchip platform



On 18/06/15 08:05, Stefan Wahren wrote:
> Hi Srinivas,
>
> Am 16.06.2015 um 12:54 schrieb Srinivas Kandagatla:
>>
>>
>> On 16/06/15 11:06, Caesar Wang wrote:
>>> Hi Srinivas,
>>>
>>> 在 2015年06月16日 17:21, Srinivas Kandagatla 写道:
>>>> Hi Stefan,
>>>>
>>>>
>>>> On 16/06/15 09:52, Stefan Wahren wrote:
>>>>> Hi Caesar,
>>>>>
>>>>> [add Maxime and Srinivas]
>>>>>
>>>>> Am 16.06.2015 um 09:27 schrieb Caesar Wang:
>>>>>> The original driver is uploaded by Jianqun.
>>>>>> Here is his patchs:
>>>>>>       https://patchwork.kernel.org/patch/5410341/
>>>>>>       https://patchwork.kernel.org/patch/5410351/
>>>>>>
>>>>>> Jianqun, nevermind!
>>>>>> I check-pick it and re-upload the driver for the upstream.
>>>>>> e.g.:
>>>>>>       Tested by on minnie board.(kernel-4.1-rc8)
>>>>>>       cd /sys/devices/platform/ffb40000.efuse
>>>>>>       localhost ffb40000.efuse # cat cpu_leakage_show
>>>>>>       cpu_version_show
>>>>>>       The results:
>>>>>>               19
>>>>>>               2
>>>>>>
>>>>>> Changes in v2:
>>>>>> - Change the document decription.
>>>>>> - Move the efuse driver into driver/soc/vendor.
>>>>>> - update the efuse driver.
>>>>>> - Add the dts node on RK3288.
>>>>>>
>>>>>>
>>>>>
>>>>> i want to mention that there is a upcoming new framework suitable for
>>>>> efuse drivers:
>>>>>
>>>>> https://lkml.org/lkml/2015/5/21/643
>>>>>
>>>>> Unfortunately i don't know the current development state.
>>>>>
>>>>
>>>> Currently this framework is used by atleast 3 drivers(qcom-tsens,
>>>> qcom-cpr, begel-bone-cape manager) which are still floating in the
>>>> mailing list.
>>>>
>>>> I was hoping that these 3 users would getback with tested-by.. which
>>>> did not happen for last 3-4 weeks.
>>>>
>>>> I would appreciate, If you could try framework too, and let me know.
>>>
>
> yes i work on OCOTP driver for MXS platform and i will try ...
>
>>
>> int rockchip_efuse_reg_read(void *context, unsigned int reg, unsigned
>> int *val)
>> {
>>      /* efuse specific read sequence */
>>      ...
>> }
>
> I will need a specific read sequence too.

You can have a look at 
https://git.linaro.org/people/srinivas.kandagatla/linux.git/blob/b4c3ad253747767511233687436f20144e850d67:/drivers/nvmem/rockchip-efuse.c

I did modify the rockchip driver, which I guess should be very much 
similar to what OCOTP driver would need.


>
> Sorry for these newbie questions:
>
> What data structure does context points to for this reg_read opteration?
>
> Do we need range checking of reg or is it handled by the framework?
>
We already have that in place.

> Are there any limitation for reg_read regarding sleeping or locking
> operations?
There are no limitaions as such from nvmem framework, regmap might have 
limitations w.r.t to sleeping and fast_io, as fast_io would take 
spinlocks, AFAIK the providers would not have fast_io, as they not IO 
devices.
>
> In case of a read only driver, is everything handle by devicetree or do
> we need an empty write operation?
Yes, if you pass read-only flag in the provider, the framework would not 
attempt to even write.

You will find answers to most of your question in the rochip-efuse.c file.


--srini
>
> Best regards
> Stefan
>
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