Patchwork ARM: imx6q: Add missing esai_ahb clock to current clock tree

login
register
mail settings
Submitter Nicolin Chen
Date Jan. 9, 2014, 3:04 a.m.
Message ID <1389236699-10387-1-git-send-email-Guangyu.Chen@freescale.com>
Download mbox | patch
Permalink /patch/308495/
State New
Headers show

Comments

Nicolin Chen - Jan. 9, 2014, 3:04 a.m.
esai_ahb clock is derived from ahb and used to provide ESAI the capability of
register accessing and FSYS clock source for I2S clocks dividing. Although the
gate of this esai_ahb is duplicated with esai clock -- the baud clock, yet
considering about the differences of their clock rates, it's quite essential
to patch this missing clock.

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
---
 Documentation/devicetree/bindings/clock/imx6q-clock.txt | 1 +
 arch/arm/mach-imx/clk-imx6q.c                           | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)
Nicolin Chen - Jan. 9, 2014, 3:49 a.m.
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
Shawn Guo - Jan. 9, 2014, 3:58 a.m.
On Thu, Jan 09, 2014 at 11:04:59AM +0800, Nicolin Chen wrote:
> esai_ahb clock is derived from ahb and used to provide ESAI the capability of
> register accessing and FSYS clock source for I2S clocks dividing. Although the
> gate of this esai_ahb is duplicated with esai clock -- the baud clock, yet
> considering about the differences of their clock rates, it's quite essential
> to patch this missing clock.
> 
> Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
> ---
>  Documentation/devicetree/bindings/clock/imx6q-clock.txt | 1 +
>  arch/arm/mach-imx/clk-imx6q.c                           | 3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/clock/imx6q-clock.txt b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> index 6aab72b..90ec91f 100644
> --- a/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> @@ -220,6 +220,7 @@ clocks and IDs.
>  	lvds2_sel		205
>  	lvds1_gate		206
>  	lvds2_gate		207
> +	esai_ahb		208
>  
>  Examples:
>  
> diff --git a/arch/arm/mach-imx/clk-imx6q.c b/arch/arm/mach-imx/clk-imx6q.c
> index af2e582..20215b9 100644
> --- a/arch/arm/mach-imx/clk-imx6q.c
> +++ b/arch/arm/mach-imx/clk-imx6q.c
> @@ -107,7 +107,7 @@ enum mx6q_clks {
>  	sata_ref, sata_ref_100m, pcie_ref, pcie_ref_125m, enet_ref, usbphy1_gate,
>  	usbphy2_gate, pll4_post_div, pll5_post_div, pll5_video_div, eim_slow,
>  	spdif, cko2_sel, cko2_podf, cko2, cko, vdoa, pll4_audio_div,
> -	lvds1_sel, lvds2_sel, lvds1_gate, lvds2_gate, clk_max
> +	lvds1_sel, lvds2_sel, lvds1_gate, lvds2_gate, esai_ahb, clk_max
>  };
>  
>  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.

Shawn

>  	clk[gpt_ipg]      = imx_clk_gate2("gpt_ipg",       "ipg",               base + 0x6c, 20);
>  	clk[gpt_ipg_per]  = imx_clk_gate2("gpt_ipg_per",   "ipg_per",           base + 0x6c, 22);
>  	if (cpu_is_imx6dl())
> -- 
> 1.8.4
> 
>
Shawn Guo - Jan. 9, 2014, 6:57 a.m.
On Thu, Jan 09, 2014 at 11:49:41AM +0800, Nicolin Chen wrote:
> 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.

Hmm, we generally leave the gate bit to the clock used to access
register, because usually it's the first one to be on and the last one
to be off.

Shawn
Nicolin Chen - Jan. 9, 2014, 7:41 a.m.
On Thu, Jan 09, 2014 at 02:57:42PM +0800, Shawn Guo wrote:
> On Thu, Jan 09, 2014 at 11:49:41AM +0800, Nicolin Chen wrote:
> > 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.
> 
> Hmm, we generally leave the gate bit to the clock used to access
> register, because usually it's the first one to be on and the last one
> to be off.

Then we should attach CLK_IGNORE_UNUSED to clk[esai] since clk[esai_ahb] is
the clock used to access memory, shouldn't we?

Thank you.
Nicolin
Nicolin Chen - Jan. 9, 2014, 7:51 a.m.
On Thu, Jan 09, 2014 at 08:58:28AM +0100, Sascha Hauer wrote:
> On Thu, Jan 09, 2014 at 03:41:38PM +0800, Nicolin Chen wrote:
> > On Thu, Jan 09, 2014 at 02:57:42PM +0800, Shawn Guo wrote:
> > > On Thu, Jan 09, 2014 at 11:49:41AM +0800, Nicolin Chen wrote:
> > > > 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.
> > > 
> > > Hmm, we generally leave the gate bit to the clock used to access
> > > register, because usually it's the first one to be on and the last one
> > > to be off.
> > 
> > Then we should attach CLK_IGNORE_UNUSED to clk[esai] since clk[esai_ahb] is
> > the clock used to access memory, shouldn't we?
> 
> Please wait for Mikes input or let's look how a proper solution can look
> like. I've already seen the case that a single bit controls multiple
> clocks. Hacking around this issue each time is not a solution.

Okay.

Thank you, Sascha.
Sascha Hauer - Jan. 9, 2014, 7:55 a.m.
[Added Mike Turquette to Cc]

On Thu, Jan 09, 2014 at 11:04:59AM +0800, Nicolin Chen wrote:
> esai_ahb clock is derived from ahb and used to provide ESAI the capability of
> register accessing and FSYS clock source for I2S clocks dividing. Although the
> gate of this esai_ahb is duplicated with esai clock -- the baud clock, yet
> considering about the differences of their clock rates, it's quite essential
> to patch this missing clock.
> 

[...]

>  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);

We have the situation here that a single bit controls two clocks. As
Shawn mentioned just using two gates on the same bit doesn't work
properly. Do we need a new basic clock type or expand the common gate
code somehow?
This situation happens from time to time and I haven't seen a solution
for this.

Sascha
Sascha Hauer - Jan. 9, 2014, 7:58 a.m.
On Thu, Jan 09, 2014 at 03:41:38PM +0800, Nicolin Chen wrote:
> On Thu, Jan 09, 2014 at 02:57:42PM +0800, Shawn Guo wrote:
> > On Thu, Jan 09, 2014 at 11:49:41AM +0800, Nicolin Chen wrote:
> > > 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.
> > 
> > Hmm, we generally leave the gate bit to the clock used to access
> > register, because usually it's the first one to be on and the last one
> > to be off.
> 
> Then we should attach CLK_IGNORE_UNUSED to clk[esai] since clk[esai_ahb] is
> the clock used to access memory, shouldn't we?

Please wait for Mikes input or let's look how a proper solution can look
like. I've already seen the case that a single bit controls multiple
clocks. Hacking around this issue each time is not a solution.

Sascha
Gerhard Sittig - Jan. 9, 2014, 2:57 p.m.
On Thu, Jan 09, 2014 at 08:55 +0100, Sascha Hauer wrote:
> 
> [ ... ]
> 
> We have the situation here that a single bit controls two clocks. As
> Shawn mentioned just using two gates on the same bit doesn't work
> properly. Do we need a new basic clock type or expand the common gate
> code somehow?
> This situation happens from time to time and I haven't seen a solution
> for this.

You may want to lookup the following message:

  Date: Tue, 23 Jul 2013 15:14:06 +0200
  From: Gerhard Sittig <gsi@denx.de>
  To: linuxppc-dev@lists.ozlabs.org, Anatolij Gustschin <agust@denx.de>,
	  Mike Turquette <mturquette@linaro.org>,
	  linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org
  Cc: [ ... ]
  Subject: Re: [PATCH v3 17/31] clk: mpc512x: introduce COMMON_CLK for MPC512x

  http://lists.infradead.org/pipermail/linux-arm-kernel/2013-July/185687.html

The specific situation was for MS-CAN on PowerPC, but it inspired
my outlining an approach to "shared clock gates".  See an example
implementation towards the end of the message with both the
clk-gate.c extension, as well as rather generic example use.

My approach turned out to not be needed, but it might serve as a
starting point for you.  You'd have to add support for static
declaration though, but this should be straight forward.


virtually yours
Gerhard Sittig
Russell King - ARM Linux - Jan. 9, 2014, 3:01 p.m.
Sascha, your messages have the Mail-Followup-To: header...

Mail-Followup-To: Nicolin Chen <Guangyu.Chen@freescale.com>,                    
        shawn.guo@linaro.org, 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, mturquette@linaro.org      

resulting in me (and others) getting mails marked as To: me where they're
not supposed to be To: me in the first place.
Sascha Hauer - Jan. 10, 2014, 10:06 a.m.
Russell,

On Thu, Jan 09, 2014 at 03:01:41PM +0000, Russell King - ARM Linux wrote:
> Sascha, your messages have the Mail-Followup-To: header...
> 
> Mail-Followup-To: Nicolin Chen <Guangyu.Chen@freescale.com>,                    
>         shawn.guo@linaro.org, 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, mturquette@linaro.org      
> 
> resulting in me (and others) getting mails marked as To: me where they're
> not supposed to be To: me in the first place.

This should be fixed with this mail.

Sascha

Patch

diff --git a/Documentation/devicetree/bindings/clock/imx6q-clock.txt b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
index 6aab72b..90ec91f 100644
--- a/Documentation/devicetree/bindings/clock/imx6q-clock.txt
+++ b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
@@ -220,6 +220,7 @@  clocks and IDs.
 	lvds2_sel		205
 	lvds1_gate		206
 	lvds2_gate		207
+	esai_ahb		208
 
 Examples:
 
diff --git a/arch/arm/mach-imx/clk-imx6q.c b/arch/arm/mach-imx/clk-imx6q.c
index af2e582..20215b9 100644
--- a/arch/arm/mach-imx/clk-imx6q.c
+++ b/arch/arm/mach-imx/clk-imx6q.c
@@ -107,7 +107,7 @@  enum mx6q_clks {
 	sata_ref, sata_ref_100m, pcie_ref, pcie_ref_125m, enet_ref, usbphy1_gate,
 	usbphy2_gate, pll4_post_div, pll5_post_div, pll5_video_div, eim_slow,
 	spdif, cko2_sel, cko2_podf, cko2, cko, vdoa, pll4_audio_div,
-	lvds1_sel, lvds2_sel, lvds1_gate, lvds2_gate, clk_max
+	lvds1_sel, lvds2_sel, lvds1_gate, lvds2_gate, esai_ahb, clk_max
 };
 
 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);
 	clk[gpt_ipg]      = imx_clk_gate2("gpt_ipg",       "ipg",               base + 0x6c, 20);
 	clk[gpt_ipg_per]  = imx_clk_gate2("gpt_ipg_per",   "ipg_per",           base + 0x6c, 22);
 	if (cpu_is_imx6dl())