linux-kernel - Re: [PATCH 1/2] opp: ti-opp-supply: Dynamically update u_volt

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Message-ID: <d86733f4-fb87-c7ce-88ff-bc2150a8acb2@ti.com>
Date:   Mon, 12 Nov 2018 16:05:47 -0600
From:   Dave Gerlach <d-gerlach@...com>
To:     "J, KEERTHY" <j-keerthy@...com>,
        Viresh Kumar <viresh.kumar@...aro.org>
CC:     <vireshk@...nel.org>, <nm@...com>, <sboyd@...nel.org>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <t-kristo@...com>
Subject: Re: [PATCH 1/2] opp: ti-opp-supply: Dynamically update u_volt_min

On 11/11/2018 09:15 PM, J, KEERTHY wrote:
> 
> 
> On 11/8/2018 11:24 AM, Viresh Kumar wrote:
>> On 07-11-18, 10:04, Keerthy wrote:
>>> The voltage range (min, max) provided in the device tree is from
>>> the data manual and is pretty big, catering to a wide range of devices.
>>> On a i2c read/write failure the regulator_set_voltage_triplet function
>>> falls back to set voltage between min and max. The min value from Device
>>> Tree can be lesser than the optimal value and in that case that can lead
>>> to a hang or crash. Hence set the u_volt_min dynamically to the optimal
>>> voltage value.
>>
>> And why shouldn't we fix the DT for this ?
> 
> The DT voltages do not cater to the broad range of devices. In some 
> particular cases the DT min voltage is slightly lower the voltage at 
> which the device cannot sustain a particular frequency in which case the 
> device just silently hangs. So best thing to do is to actually read the 
> device specific voltages dynamically which will guarantee a particular 
> device sustaining a particular frequency at the optimal voltage.
> 

Acked-by: Dave Gerlach <d-gerlach@...com>

>>