From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752685AbcD0C5Y (ORCPT <rfc822;w@1wt.eu>);
	Tue, 26 Apr 2016 22:57:24 -0400
Received: from mail-qg0-f68.google.com ([209.85.192.68]:35485 "EHLO
	mail-qg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751710AbcD0C5W (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 26 Apr 2016 22:57:22 -0400
MIME-Version: 1.0
In-Reply-To: <20160427015835.GE30692@tiger>
References: <1454107764-19876-1-git-send-email-stefan@agner.ch>
	<20160421034520.GA19965@shlinux2.ap.freescale.net>
	<20160426012341.GB8870@tiger>
	<CAA+hA=QTNEAaMfjJoMMO5gPR8VPYBWYx=HZgjngUFJK4LxMp=g@mail.gmail.com>
	<1461663072.7839.17.camel@pengutronix.de>
	<CAA+hA=SSQJPbzbhCY7O8JaxiUgMDjG2ATQXsCW-X5zc2inC6kw@mail.gmail.com>
	<CAA+hA=Q5Un7Sib5QEvK4H2PH5qrySAkRR+=ofuaKxX_PCuT-Yw@mail.gmail.com>
	<20160427015835.GE30692@tiger>
Date: Wed, 27 Apr 2016 10:57:21 +0800
Message-ID: <CAA+hA=REqJ8JhmKt5_jCAaRTUy2E14ww_MqWSSLpNBKgnf=U9A@mail.gmail.com>
Subject: Re: [PATCH 1/2] clk: imx: do not sleep if IRQ's are still disabled
From: Dong Aisheng <dongas86@gmail.com>
To: Shawn Guo <shawnguo@kernel.org>
Cc: Lucas Stach <l.stach@pengutronix.de>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Stefan Agner <stefan@agner.ch>, mingo@redhat.com,
        "kernel@pengutronix.de" <kernel@pengutronix.de>, tglx@linutronix.de,
        linux-clk@vger.kernel.org,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Apr 27, 2016 at 9:58 AM, Shawn Guo <shawnguo@kernel.org> wrote:
> On Tue, Apr 26, 2016 at 07:27:03PM +0800, Dong Aisheng wrote:
>> Shawn,
>> What's your suggestion?
>
> I think this needs more discussion, and I just dropped Stefan's patch
> from my tree.
>
> We need to firstly understand why this is happening.  The .prepare hook
> is defined to be non-atomic context, and so that we call sleep function
> in there.  We did everything right.  Why are we getting the warning?  If
> I'm correct, this warning only happens on i.MX7D.  Why is that?
>

Why Stefan's patch works (checking irqs_disabled()) is because during kernel
time init, the irq is still not enabled. It fixes the issue indirectly.
See:
asmlinkage __visible void __init start_kernel(void)
{
        /*
         * Set up the scheduler prior starting any interrupts (such as the
         * timer interrupt). Full topology setup happens at smp_init()
         * time - but meanwhile we still have a functioning scheduler.
         */
        sched_init();
        .............
        time_init();
        ..............
        WARN(!irqs_disabled(), "Interrupts were enabled early\n");
        early_boot_irqs_disabled = false;
        local_irq_enable();
}

The issue can only happen when PLL enable causes a schedule during
imx_clock_init().
Not all PLL has this issue.
The issue happens on MX7D pll_audio_main_clk/pll_video_main_clk
which requires more delay time and cause usleep.
Because clk framework does not support MX7D clock types (operation requires
parents on), we simply enable all clocks in imx7d_clocks_init().

If apply my this patch series:
https://lkml.org/lkml/2016/4/20/199
The issue can also be gone.

Regards
Dong Aisheng

> Shawn