linux-kernel - Re: [RFC v2 2/3] drivers: nvmem: Add QTI qfprom-efuse support

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Date:   Mon, 15 Jun 2020 11:44:35 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Doug Anderson <dianders@...omium.org>,
        Ravi Kumar Bokka <rbokka@...eaurora.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        dhavalp@...eaurora.org, mturney@...eaurora.org,
        sparate@...eaurora.org, c_rbokka@...eaurora.org,
        mkurumel@...eaurora.org
Subject: Re: [RFC v2 2/3] drivers: nvmem: Add QTI qfprom-efuse support



On 13/06/2020 21:33, Doug Anderson wrote:
> Hi,
> 
> On Thu, Jun 11, 2020 at 2:49 AM Ravi Kumar Bokka <rbokka@...eaurora.org> wrote:
>>
>> This patch adds support for QTI qfprom-efuse controller. This driver can
>> access the raw qfprom regions for fuse blowing.
>>
>> The current existed qfprom driver is only supports for cpufreq, thermal sensors
>> drivers by read out calibration data, speed bins..etc which is stored
>> by qfprom efuses.
>>
>> Signed-off-by: Ravi Kumar Bokka <rbokka@...eaurora.org>
>> ---
> 
> It makes all your code reviewers much happier (and much more likely to
> take the time to review your patches) if you include a changelog with
> what changed from one version to the next.  If you would like some
> help maintaining such a thing, might I suggest "patman":
> 
> https://gitlab.denx.de/u-boot/u-boot/-/blob/master/tools/patman/README
> 
> ...pay no mind that it's hosted in the U-Boot repo--it's really quite
> a great tool.
> 
> 
>>   drivers/nvmem/Kconfig  |   1 +
>>   drivers/nvmem/qfprom.c | 405 ++++++++++++++++++++++++++++++++++++++++++++++---
>>   2 files changed, 385 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
>> index d7b7f6d..623d59e 100644
>> --- a/drivers/nvmem/Kconfig
>> +++ b/drivers/nvmem/Kconfig
>> @@ -117,6 +117,7 @@ config QCOM_QFPROM
>>          help
>>            Say y here to enable QFPROM support. The QFPROM provides access
>>            functions for QFPROM data to rest of the drivers via nvmem interface.
>> +         And this driver provides access QTI qfprom efuse via nvmem interface.
> 
> I'm not sure it was necessary to add that line, but I won't object if
> you/others really like it.
> 

NAK from my side!

> 
>>            This driver can also be built as a module. If so, the module
>>            will be called nvmem_qfprom.
>> diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
>> index 8a91717..312318c 100644
>> --- a/drivers/nvmem/qfprom.c
>> +++ b/drivers/nvmem/qfprom.c
> 
> You've still mostly not addressed most of the review feedback I've now
> given you 3 times.  Rather than repeating comments, I have simply
> provided a patch that makes the driver into a state that I'm happy
> with:
> 
> https://crrev.com/c/2244932
> 
> Rough summary:
> 
> * There should be no reason to provide "reset" values for things.  For
> anything that you change for fuse blowing, just save and restore
> after.
> 
> * Use the major/minor version read from 0x6000 to pick the parameters
> to use.  Please double-check that I got this right.
> 
> * Reading should still read "corrected", not "raw".  Added a sysfs
> knob to allow you to read "raw", though.

We could create an additional nvmem read-only provider in future if 
required to read raw!.

> 
> * Simplified the SoC data structure.
> 
> * No need for quite so many levels of abstraction for setting clocks /
> regulator.
> 
> * Don't set regulator voltage.  Rely on device tree to make sure it's right.
> 
> * Properly undo things in the case of failure.
> 
> * Don't just keep enabling the regulator over and over again.
> 
> * Enable / disable the clock each time; now we don't need a .remove
> function and yet we still don't leave the clock enabled/prepared.
> 
> * Polling every 100 us but timing out in 10 us didn't make sense.
> Swap those.  Also no reason for 100 us to be SoC specific.
> 
> * No need for reg-names.
> 
> * We shouldn't be creating two separate nvmem devices.
> 
> 
> In general I'm happy to post my series to the list myself to get
> review feedback.  For now I'm expecting that you can squash my changes
> in and send the next version.
> 
> 
> -Doug
>