Re: [pm_wip/voltdm_nm][PATCH v2 2/3] OMAP4: PM: VC: introduce concept of default channel

[Kevin Hilman <khilman@ti.com>]

"Menon, Nishanth" <nm@ti.com> writes:

> On Thu, Jun 2, 2011 at 18:45, Kevin Hilman <khilman@ti.com> wrote:
>> Nishanth Menon <nm@ti.com> writes:
>>
>>> Due to a TRM bug, the current code assumes that channel0(core) is the default
>>> channel. With the additional explanation provided by the hardware team, it is
>>> clear that PRM_VC_CFG_CHANNEL register allows for flexibility of configuring
>>> for various PMIC configurations. For example, the I2C slave address on TWL6030
>>> when using 4430 configuration could potentially use the same slave address for
>>> all domains, while in 4460 configuration, we drive MPU using TPS; Core and IVA
>>> using TWL6030. To allow this flexibility, we state in existing parameters using
>>> a flag to indicate usage of default channel.
>>>
>>> In addition, the TRM update clears up the confusion on the fact that MPU is
>>> infact the default channel on OMAP4.
>>>
>>> We update the same here.
>>>
>>> Signed-off-by: Nishanth Menon <nm@ti.com>
>>
>> There's too much going on in this patch not described in the changelog
>> (extra error checking, volt & cmd reg checking etc.)
>>
>> Also, I don't like the USE_DEFAULT_CHANNEL_I2C_PARAM, mainly because it
>> adds clutter without any obvious value.  To me, zero is a perfectly good
>> value to signify "use default channel value", especially since that's
>> the value used by the hardware.
> The reason is that 0 is a valid i2c register address. 8 bits is used
> in VC and I wanted one bit which was further away, hence the 16 bit.
> The usage could be that in .volt_reg_addr or in .cmd_reg_addr I could
> set this up with the macro. and bingo, we use the default domain's
> configuration.
>
> This is esp useful if we had a single pmic reg for all domains.. I
> mean the VC design allows for it, even though we dont use it
> currently.

OK.

See, it's easy to convince me that something is needed/useful.  Of
course, I prefer to be conviced by the changelog. :)  

Please make this feature into a dedicated patch with an appropriately
descriptive changelog.  Thanks.

>>
>> Incidentally, adding this doesn't actually change current behavior.
>> Currently, I use zero (an unconfigured value in the VC settings) to
>> signify it should use default settings.  In your patch, you defined
>> USE_DEFAULT_CHANNEL_I2C_PARAM as 0x10000 (17 bits) but assign it to 16
>> bit fields, which means they are just set to zero. :)
>
>
>> So rather than take this patch, I'm just going to fold the following
>> diff into "OMAP3+: VC: abstract out channel configuration" in voltdm_b.
>> I'll also update the changelog noting that the TRM is wrong here in that
>> it describes CORE as the default channel when it's in fact MPU.
>
> I intend to post a new series including my PMIC changes as well early
> next week(mondayish hopefully). Can we hold off review of any further
> of my voltage fixes patches till then?
>

Sure.  It's the first time anyone as asked me not to review patches. :)
I'll gladly comply.

I've already folded the minimal change I proposed into the original
patch locally, and will push updated voltdm_* branches by the end of
today.

Kevin
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html