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From: Guangyu.Chen@freescale.com (Nicolin Chen)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: imx6q: Add missing esai_ahb clock to current clock tree
Date: Thu, 9 Jan 2014 11:49:41 +0800	[thread overview]
Message-ID: <20140109034940.GA14480@MrMyself> (raw)
In-Reply-To: <20140109035810.GB21717@S2101-09.ap.freescale.net>

On Thu, Jan 09, 2014 at 11:58:12AM +0800, Shawn Guo wrote:
> >  static struct clk *clk[clk_max];
> > @@ -355,6 +355,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
> >  	clk[ecspi5]       = imx_clk_gate2("ecspi5",        "ecspi_root",        base + 0x6c, 8);
> >  	clk[enet]         = imx_clk_gate2("enet",          "ipg",               base + 0x6c, 10);
> >  	clk[esai]         = imx_clk_gate2("esai",          "esai_podf",         base + 0x6c, 16);
> > +	clk[esai_ahb]     = imx_clk_gate2("esai_ahb",      "ahb",               base + 0x6c, 16);
> 
> Hmm, having two clocks operating on the same gate bit will get us
> problem in clock disabling.  Clock enabling is fine, since either
> one who calls clk_enable() first will just set the gate bit.  But in
> case that clk_enable() is called on both clocks, and then when either
> clock calls clk_disable(), the gate bit will be cleared and thus breaks
> the other one that might still be in use.

Understood. But how could we handle this situation? The only way I can figure
out is to make sure the driver open/close them at the same time, it's not a
perfect way though.

Nicolin

WARNING: multiple messages have this Message-ID (diff)
From: Nicolin Chen <Guangyu.Chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
To: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org,
	linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org,
	pawel.moll-5wv7dgnIgG8@public.gmane.org,
	mark.rutland-5wv7dgnIgG8@public.gmane.org,
	ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org,
	galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	rob-VoJi6FS/r0vR7s880joybQ@public.gmane.org
Subject: Re: [PATCH] ARM: imx6q: Add missing esai_ahb clock to current clock tree
Date: Thu, 9 Jan 2014 11:49:41 +0800	[thread overview]
Message-ID: <20140109034940.GA14480@MrMyself> (raw)
In-Reply-To: <20140109035810.GB21717-rvtDTF3kK1ictlrPMvKcciBecyulp+rMXqFh9Ls21Oc@public.gmane.org>

On Thu, Jan 09, 2014 at 11:58:12AM +0800, Shawn Guo wrote:
> >  static struct clk *clk[clk_max];
> > @@ -355,6 +355,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
> >  	clk[ecspi5]       = imx_clk_gate2("ecspi5",        "ecspi_root",        base + 0x6c, 8);
> >  	clk[enet]         = imx_clk_gate2("enet",          "ipg",               base + 0x6c, 10);
> >  	clk[esai]         = imx_clk_gate2("esai",          "esai_podf",         base + 0x6c, 16);
> > +	clk[esai_ahb]     = imx_clk_gate2("esai_ahb",      "ahb",               base + 0x6c, 16);
> 
> Hmm, having two clocks operating on the same gate bit will get us
> problem in clock disabling.  Clock enabling is fine, since either
> one who calls clk_enable() first will just set the gate bit.  But in
> case that clk_enable() is called on both clocks, and then when either
> clock calls clk_disable(), the gate bit will be cleared and thus breaks
> the other one that might still be in use.

Understood. But how could we handle this situation? The only way I can figure
out is to make sure the driver open/close them at the same time, it's not a
perfect way though.

Nicolin



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WARNING: multiple messages have this Message-ID (diff)
From: Nicolin Chen <Guangyu.Chen@freescale.com>
To: Shawn Guo <shawn.guo@linaro.org>
Cc: <kernel@pengutronix.de>, <linux@arm.linux.org.uk>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <rob.herring@calxeda.com>,
	<pawel.moll@arm.com>, <mark.rutland@arm.com>,
	<ijc+devicetree@hellion.org.uk>, <galak@codeaurora.org>,
	<devicetree@vger.kernel.org>, <rob@landley.net>
Subject: Re: [PATCH] ARM: imx6q: Add missing esai_ahb clock to current clock tree
Date: Thu, 9 Jan 2014 11:49:41 +0800	[thread overview]
Message-ID: <20140109034940.GA14480@MrMyself> (raw)
In-Reply-To: <20140109035810.GB21717@S2101-09.ap.freescale.net>

On Thu, Jan 09, 2014 at 11:58:12AM +0800, Shawn Guo wrote:
> >  static struct clk *clk[clk_max];
> > @@ -355,6 +355,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
> >  	clk[ecspi5]       = imx_clk_gate2("ecspi5",        "ecspi_root",        base + 0x6c, 8);
> >  	clk[enet]         = imx_clk_gate2("enet",          "ipg",               base + 0x6c, 10);
> >  	clk[esai]         = imx_clk_gate2("esai",          "esai_podf",         base + 0x6c, 16);
> > +	clk[esai_ahb]     = imx_clk_gate2("esai_ahb",      "ahb",               base + 0x6c, 16);
> 
> Hmm, having two clocks operating on the same gate bit will get us
> problem in clock disabling.  Clock enabling is fine, since either
> one who calls clk_enable() first will just set the gate bit.  But in
> case that clk_enable() is called on both clocks, and then when either
> clock calls clk_disable(), the gate bit will be cleared and thus breaks
> the other one that might still be in use.

Understood. But how could we handle this situation? The only way I can figure
out is to make sure the driver open/close them at the same time, it's not a
perfect way though.

Nicolin




  reply	other threads:[~2014-01-09  3:49 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-09  3:04 [PATCH] ARM: imx6q: Add missing esai_ahb clock to current clock tree Nicolin Chen
2014-01-09  3:04 ` Nicolin Chen
2014-01-09  3:04 ` Nicolin Chen
2014-01-09  3:58 ` Shawn Guo
2014-01-09  3:58   ` Shawn Guo
2014-01-09  3:58   ` Shawn Guo
2014-01-09  3:49   ` Nicolin Chen [this message]
2014-01-09  3:49     ` Nicolin Chen
2014-01-09  3:49     ` Nicolin Chen
2014-01-09  6:57     ` Shawn Guo
2014-01-09  6:57       ` Shawn Guo
2014-01-09  6:57       ` Shawn Guo
2014-01-09  7:41       ` Nicolin Chen
2014-01-09  7:41         ` Nicolin Chen
2014-01-09  7:41         ` Nicolin Chen
2014-01-09  7:58         ` Sascha Hauer
2014-01-09  7:58           ` Sascha Hauer
2014-01-09  7:58           ` Sascha Hauer
2014-01-09  7:51           ` Nicolin Chen
2014-01-09  7:51             ` Nicolin Chen
2014-01-09  7:51             ` Nicolin Chen
2014-01-09  7:55 ` Sascha Hauer
2014-01-09  7:55   ` Sascha Hauer
2014-01-09  7:55   ` Sascha Hauer
2014-01-09 14:57   ` Gerhard Sittig
2014-01-09 14:57     ` Gerhard Sittig
2014-01-09 14:57     ` Gerhard Sittig
2014-01-09 15:01   ` Russell King - ARM Linux
2014-01-09 15:01     ` Russell King - ARM Linux
2014-01-09 15:01     ` Russell King - ARM Linux
2014-01-10 10:06     ` Sascha Hauer
2014-01-10 10:06       ` Sascha Hauer
2014-01-10 10:06       ` Sascha Hauer

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