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From: sboyd@codeaurora.org (Stephen Boyd)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH V3 3/8] clk: core: support clocks which requires parents enable (part 1)
Date: Fri, 1 Jul 2016 17:44:26 -0700	[thread overview]
Message-ID: <20160702004426.GL27880@codeaurora.org> (raw)
In-Reply-To: <1467279078-2330-4-git-send-email-aisheng.dong@nxp.com>

On 06/30, Dong Aisheng wrote:
> On Freescale i.MX7D platform, all clocks operations, including
> enable/disable, rate change and re-parent, requires its parent
> clock enable. Current clock core can not support it well.
> This patch introduce a new flag CLK_OPS_PARENT_ENABLE to handle this
> special case in clock core that enable its parent clock firstly for
> each operation and disable it later after operation complete.
> 
> The patch part 1 fixes the possible disabling clocks while its parent
> is off during kernel booting phase in clk_disable_unused_subtree().
> 
> Before the completion of kernel booting, clock tree is still not built
> completely, there may be a case that the child clock is on but its
> parent is off which could be caused by either HW initial reset state
> or bootloader initialization.
> 
> Taking bootloader as an example, we may enable all clocks in HW by default.
> And during kernel booting time, the parent clock could be disabled in its
> driver probe due to calling clk_prepare_enable and clk_disable_unprepare.
> Because it's child clock is only enabled in HW while its SW usecount
> in clock tree is still 0, so clk_disable of parent clock will gate
> the parent clock in both HW and SW usecount ultimately. Then there will
> be a child clock is still on in HW but its parent is already off.
> 
> Later in clk_disable_unused(), this clock disable accessing while its
> parent off will cause system hang due to the limitation of HW which
> must require its parent on.
> 
> This patch simply enables the parent clock first before disabling
> if flag CLK_OPS_PARENT_ENABLE is set in clk_disable_unused_subtree().
> This is a simple solution and only affects booting time.
> 
> After kernel booting up the clock tree is already created, there will
> be no case that child is off but its parent is off.
> So no need do this checking for normal clk_disable() later.
> 
> Cc: Michael Turquette <mturquette@baylibre.com>
> Cc: Stephen Boyd <sboyd@codeaurora.org>
> Cc: Shawn Guo <shawnguo@kernel.org>
> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> ---

Applied to clk-next

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

  reply	other threads:[~2016-07-02  0:44 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-30  9:31 [PATCH V3 0/8] clk: core: support clocks which requires parents enable Dong Aisheng
2016-06-30  9:31 ` [PATCH V3 1/8] clk: introduce clk_core_enable_lock and clk_core_disable_lock functions Dong Aisheng
2016-07-02  0:44   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 2/8] clk: move clk_disable_unused after clk_core_disable_unprepare function Dong Aisheng
2016-07-02  0:44   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 3/8] clk: core: support clocks which requires parents enable (part 1) Dong Aisheng
2016-07-02  0:44   ` Stephen Boyd [this message]
2016-06-30  9:31 ` [PATCH V3 4/8] clk: core: support clocks which requires parents enable (part 2) Dong Aisheng
2016-07-02  0:45   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 5/8] clk: imx: re-order and concentrate the same type of clk api Dong Aisheng
2016-07-02  0:45   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 6/8] clk: imx: add clk api for supporting CLK_OPS_PARENT_ENABLE clocks Dong Aisheng
2016-07-02  0:45   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 7/8] clk: imx7d: using api with flag CLK_OPS_PARENT_ENABLE Dong Aisheng
2016-07-02  0:45   ` Stephen Boyd
2016-06-30  9:31 ` [PATCH V3 8/8] clk: imx7d: only enable minimum required clocks Dong Aisheng
2016-07-02  0:45   ` Stephen Boyd

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