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

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Message-ID: <55828A7D.1080202@rock-chips.com>
Date:	Thu, 18 Jun 2015 17:08:13 +0800
From:	Caesar Wang <wxt@...k-chips.com>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Stefan Wahren <stefan.wahren@...e.com>
CC:	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



在 2015年06月18日 16:29, Srinivas Kandagatla 写道:
>
>
> 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.

That rockchip-efuse.c driver shouldn't be work.

An entire 8-bit word of data can be read in one read operation with 
STROBE being high and a proper address
selected (address signals A5~A7 are “don’t cares”).

That's great if we can get the content from the .reg_read when the 
consumer driver
callback the nvmem_cell_read().

e.g.:
static struct regmap_config rockchip_efuse_regmap_config = {
     .reg_bits = 32,
     .val_bits = 8,
     .reg_stride = 1,
     .reg_read = rockchip_efuse_reg_read,
};
...
/ * consumer driver */
nvmem_cell_get()/nvmem_cell_put();
nvmem_cell_read()/nvmem_cell_write();
........


>
>
>>
>> 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
>>
>
>
>

-- 
Thanks,
- Caesar


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