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From: treding@nvidia.com (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] ARM: multi_v7_defconfig: enable CONFIG_PWM_ROCKCHIP=y
Date: Mon, 14 Mar 2016 13:18:24 +0100	[thread overview]
Message-ID: <20160314121823.GE22912@ulmo.nvidia.com> (raw)
In-Reply-To: <1457787029-9168-1-git-send-email-andy.yan@kernel-upstream.org>

On Sat, Mar 12, 2016 at 08:50:29PM +0800, Andy Yan wrote:
> All the current rk3066 based boards use pwm modulate vdd_logic
> voltage, the board may hang when the system boot and run to a higher
> frequency without pwm enabled, so enable it as builtin.

I don't understand the rationale here. Surely if the system can't safely
switch to a higher frequency because the regulator isn't available, then
it should be prevented from switching, shouldn't it?

Making this change alone will not prevent users from switching this back
to =m on their own. So either you need to add code to prevent a switch
to an unsupported frequency in the absence of the regulator, or you need
to change the PWM_ROCKCHIP Kconfig option to be bool instead, though the
latter is of course a somewhat ugly hack, whereas the former would be a
proper fix.

Thierry
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WARNING: multiple messages have this Message-ID (diff)
From: Thierry Reding <treding@nvidia.com>
To: Andy Yan <andy.yan@kernel-upstream.org>
Cc: <arnd@arndb.de>, <javier@osg.samsung.com>, <kgene@kernel.org>,
	<k.kozlowski@samsung.com>, <geert+renesas@glider.be>,
	<linux-kernel@vger.kernel.org>, <public_timo.s@silentcreek.de>,
	<linux@arm.linux.org.uk>, <alexandre.belloni@free-electrons.com>,
	<sjoerd.simons@collabora.co.uk>, <olof@lixom.net>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] ARM: multi_v7_defconfig: enable CONFIG_PWM_ROCKCHIP=y
Date: Mon, 14 Mar 2016 13:18:24 +0100	[thread overview]
Message-ID: <20160314121823.GE22912@ulmo.nvidia.com> (raw)
In-Reply-To: <1457787029-9168-1-git-send-email-andy.yan@kernel-upstream.org>

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On Sat, Mar 12, 2016 at 08:50:29PM +0800, Andy Yan wrote:
> All the current rk3066 based boards use pwm modulate vdd_logic
> voltage, the board may hang when the system boot and run to a higher
> frequency without pwm enabled, so enable it as builtin.

I don't understand the rationale here. Surely if the system can't safely
switch to a higher frequency because the regulator isn't available, then
it should be prevented from switching, shouldn't it?

Making this change alone will not prevent users from switching this back
to =m on their own. So either you need to add code to prevent a switch
to an unsupported frequency in the absence of the regulator, or you need
to change the PWM_ROCKCHIP Kconfig option to be bool instead, though the
latter is of course a somewhat ugly hack, whereas the former would be a
proper fix.

Thierry

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  parent reply	other threads:[~2016-03-14 12:18 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-12 12:50 [PATCH 1/2] ARM: multi_v7_defconfig: enable CONFIG_PWM_ROCKCHIP=y Andy Yan
2016-03-12 12:50 ` Andy Yan
2016-03-12 12:51 ` [PATCH 2/2] ARM: multi_v7_defconfig: enable CONFIG_REGULATOR_PWM=y Andy Yan
2016-03-12 12:51   ` Andy Yan
2016-03-14 12:21   ` Thierry Reding
2016-03-14 12:21     ` Thierry Reding
2016-03-14 12:18 ` Thierry Reding [this message]
2016-03-14 12:18   ` [PATCH 1/2] ARM: multi_v7_defconfig: enable CONFIG_PWM_ROCKCHIP=y Thierry Reding

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