linux-kernel - RE: [PATCH 1/3] clk: qcom: gdsc: Add support for gdscs with HW control

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Date:   Wed, 2 Nov 2016 12:23:43 +0530
From:   "Sricharan" <sricharan@...eaurora.org>
To:     "'Stephen Boyd'" <sboyd@...eaurora.org>
Cc:     <mturquette@...libre.com>, <linux-clk@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <rnayak@...eaurora.org>, <stanimir.varbanov@...aro.org>
Subject: RE: [PATCH 1/3] clk: qcom: gdsc: Add support for gdscs with HW control

Hi,

>-----Original Message-----
>From: linux-arm-msm-owner@...r.kernel.org [mailto:linux-arm-msm-owner@...r.kernel.org] On Behalf Of Sricharan
>Sent: Wednesday, November 02, 2016 12:21 PM
>To: 'Stephen Boyd' <sboyd@...eaurora.org>
>Cc: mturquette@...libre.com; linux-clk@...r.kernel.org; linux-arm-msm@...r.kernel.org; linux-kernel@...r.kernel.org;
>rnayak@...eaurora.org; stanimir.varbanov@...aro.org
>Subject: RE: [PATCH 1/3] clk: qcom: gdsc: Add support for gdscs with HW control
>
>Hi Stephen,
>
>>On 10/24, Sricharan R wrote:
>>> @@ -164,6 +171,10 @@ static int gdsc_enable(struct generic_pm_domain *domain)
>>>  	 */
>>>  	udelay(1);
>>>
>>> +	/* Turn on HW trigger mode if supported */
>>> +	if (sc->flags & HW_CTRL)
>>> +		gdsc_hwctrl(sc, true);
>>> +
>>
>>It sounds like this will cause glitches if the hardware isn't
>>asserting their hw control bit by default? This has me concerned
>>that we can't just throw the hw control enable part into here,
>>because that bit doesn't live in the clock controller, instead it
>>lives in the hw block that is powered by the power domain?
>>
>>Or does the power on reset value of that hw control signal
>>asserted? If that's true then we should be ok to force it into hw
>>control mode by default.
>>
>
>The hw control bit is set by default. Instead its turned 'off'
>with the reset value. So it has to not
>be turned 'on' at some point
>to put the gdsc in hw control if required. This bit is part of the
>gdscr register. So i did not quite understand the reason for the
>glitch here ?
>

typo above, i meant it has to be turned 'on' at some point
if required.

Regards,
 Sricharan