Re: [PATCH v2 4/5] ARM: dts: omap5: describe control for ckobuffer

Tero Kristo <t-kristo@xxxxxx> · Thu, 28 Apr 2016 16:23:41 +0300

On 28/04/16 12:12, H. Nikolaus Schaller wrote:
Hi Tero,

Am 28.04.2016 um 10:03 schrieb Tero Kristo <t-kristo@xxxxxx>:

On 27/04/16 17:35, H. Nikolaus Schaller wrote:
HI,

Am 27.04.2016 um 16:23 schrieb Peter Ujfalusi <peter.ujfalusi@xxxxxx>:

On 04/27/2016 05:10 PM, Tero Kristo wrote:
On 27/04/16 16:10, H. Nikolaus Schaller wrote:

Am 27.04.2016 um 14:31 schrieb Tero Kristo <t-kristo@xxxxxx>:

On 27/04/16 09:04, H. Nikolaus Schaller wrote:

Am 26.04.2016 um 19:27 schrieb Tony Lindgren <tony@xxxxxxxxxxx>:

Tero,

* H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> [160418 11:23]:
OMAP5 has a register to control if the ckobuffer is enabled
and defines the polarity. ckobuffer is required to drive a twl6040
with the system clock. Hence, add the pinctrl,single to the
OMAP5 SoC description so that omap5-board-common can
set up the ckobuffer as required.

Is this really a mux or should it be a mux clock?

It is a pinmux setting for the clock out buffer to choose what signal
(and polarity) is presented on the fref_xtal_clk pad.

The register is part of the CTRL_MODULE_WKUP.
The clock signal is the xtal master clock of the whole SoC.

Although there is a bit to choose an alternate clock, there is no
alternate in the OMAP5 silicon.

Therefore I would say it is about padconf and not clock or clock mux
related.

It just happens to be a clock signal which can be routed to this
pad.

The two could very well be implemented as clock nodes, a mux and a gate.
This would describe the hardware functionality better imo, if the
assumptions made here are correct. Implementing the control as pinctrl
hacks looks rather weird to me.

Why do you consider it a "pinctrl hack"? IMHO it is not a hack, but 100%
proper use of pinctrl.

It is just the level of abstraction we are talking about here. If it is a
clock we are controlling, we should rather control it as a clock (higher level
abstraction), not a pin.

I second this. I think it is better to have a simple gate clock and handle
only CONTROL_CKOBUFFER:CKOBUFFER_CLK_EN (bit 28) only as the other bits does
not have real use.

Then we can add clk API support for this. On most OMAP4 devices the clock is
always on,

this is why I am raising the question if we really want to control it on the omap5 or just
turn it on for all omap5 boards like the omap4 appears to do... I.e. if turning the pin on
as a pinctrl is IMHO sufficient for all practical purposes.

so the board DTS file need to provide a dummy clock, or we can make
the high precision clock also as optional (on panda both OMAP4 and twl6040
uses the same reference clock).

Hm. It looks as if implementing this (and clock gating) is beyond my experiences.
But I am happy to test a proposal on our omap5 board.

BR and thanks,
Nikolaus

See the inline patch, this implements the fref_xtal_ck. I had to add some kernel code also to cope with the new SCM area, but the same area can now be accessed via syscon also if needed.

Looks interesting, although quite complex to enable a single SoC pad at boot time...

Yea it gives plenty of other things for you also. syscon, integration 
with clock framework, etc.


Will asap study how it works and test. And of course report results.

Thanks, Tero.


Thanks and BR,
Nikolaus


From: Tero Kristo <t-kristo@xxxxxx>
Date: Thu, 28 Apr 2016 11:00:57 +0300
Subject: [PATCH] ARM: omap5: add support for fref_xtal_ck

Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
---
arch/arm/boot/dts/omap5.dtsi           | 22 ++++++++++++++++++++++
arch/arm/boot/dts/omap54xx-clocks.dtsi | 10 ++++++++++
arch/arm/mach-omap2/control.c          | 20 ++++++++++++++++----
include/linux/clk/ti.h                 |  1 +
4 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
index 38805eb..bdc6528 100644
--- a/arch/arm/boot/dts/omap5.dtsi
+++ b/arch/arm/boot/dts/omap5.dtsi
@@ -277,6 +277,28 @@
				pinctrl-single,register-width = <16>;
				pinctrl-single,function-mask = <0x7fff>;
			};
+
+			omap5_scm_wkup_pad_conf: omap5_scm_wkup_pad_conf@cda0 {
+				compatible = "ti,omap5-scm-wkup-pad-conf",
+					     "simple-bus";
+				reg = <0xcda0 0x60>;
+				#address-cells = <1>;
+				#size-cells = <1>;
+				ranges = <0 0xcda0 0x60>;
+
+				scm_wkup_pad_conf: scm_conf@0 {
+					compatible = "syscon", "simple-bus";
+					reg = <0x0 0x60>;
+					#address-cells = <1>;
+					#size-cells = <1>;
+					ranges = <0 0x0 0x60>;
+
+					scm_wkup_pad_conf_clocks: clocks@0 {
+						#address-cells = <1>;
+						#size-cells = <0>;
+					};
+				};
+			};
		};

		ocmcram: ocmcram@40300000 {
diff --git a/arch/arm/boot/dts/omap54xx-clocks.dtsi b/arch/arm/boot/dts/omap54xx-clocks.dtsi
index 83b425f..f970dac 100644
--- a/arch/arm/boot/dts/omap54xx-clocks.dtsi
+++ b/arch/arm/boot/dts/omap54xx-clocks.dtsi
@@ -1388,3 +1388,13 @@
		reg = <0x021c>;
	};
};
+
+&scm_wkup_pad_conf_clocks {
+	fref_xtal_ck: fref_xtal_ck {
+		#clocks-cells = <0>;
+		compatible = "ti,gate-clock";
+		clocks = <&sys_clkin>;
+		ti,bit-shift = <28>;
+		reg = <0x14>;
+	};
+};
diff --git a/arch/arm/mach-omap2/control.c b/arch/arm/mach-omap2/control.c
index 1662071..5956641 100644
--- a/arch/arm/mach-omap2/control.c
+++ b/arch/arm/mach-omap2/control.c
@@ -623,6 +623,7 @@ void __init omap3_ctrl_init(void)

struct control_init_data {
	int index;
+	void __iomem *mem;
	s16 offset;
};

@@ -635,6 +636,10 @@ static const struct control_init_data omap2_ctrl_data = {
	.offset = -OMAP2_CONTROL_GENERAL,
};

+static const struct control_init_data ctrl_aux_data = {
+	.index = TI_CLKM_CTRL_AUX,
+};
+
static const struct of_device_id omap_scrm_dt_match_table[] = {
	{ .compatible = "ti,am3-scm", .data = &ctrl_data },
	{ .compatible = "ti,am4-scm", .data = &ctrl_data },
@@ -644,6 +649,7 @@ static const struct of_device_id omap_scrm_dt_match_table[] = {
	{ .compatible = "ti,dm816-scrm", .data = &ctrl_data },
	{ .compatible = "ti,omap4-scm-core", .data = &ctrl_data },
	{ .compatible = "ti,omap5-scm-core", .data = &ctrl_data },
+	{ .compatible = "ti,omap5-scm-wkup-pad-conf", .data = &ctrl_aux_data },
	{ .compatible = "ti,dra7-scm-core", .data = &ctrl_data },
	{ }
};
@@ -660,15 +666,21 @@ int __init omap2_control_base_init(void)
	struct device_node *np;
	const struct of_device_id *match;
	struct control_init_data *data;
+	void __iomem *mem;

	for_each_matching_node_and_match(np, omap_scrm_dt_match_table, &match) {
		data = (struct control_init_data *)match->data;

-		omap2_ctrl_base = of_iomap(np, 0);
-		if (!omap2_ctrl_base)
+		mem = of_iomap(np, 0);
+		if (!mem)
			return -ENOMEM;

-		omap2_ctrl_offset = data->offset;
+		if (data->index == TI_CLKM_CTRL) {
+			omap2_ctrl_base = mem;
+			omap2_ctrl_offset = data->offset;
+		}
+
+		data->mem = mem;
	}

	return 0;
@@ -713,7 +725,7 @@ int __init omap_control_init(void)
		} else {
			/* No scm_conf found, direct access */
			ret = omap2_clk_provider_init(np, data->index, NULL,
-						      omap2_ctrl_base);
+						      data->mem);
			if (ret)
				return ret;
		}
diff --git a/include/linux/clk/ti.h b/include/linux/clk/ti.h
index dc5164a..be25aa8 100644
--- a/include/linux/clk/ti.h
+++ b/include/linux/clk/ti.h
@@ -195,6 +195,7 @@ enum {
	TI_CLKM_PRM,
	TI_CLKM_SCRM,
	TI_CLKM_CTRL,
+	TI_CLKM_CTRL_AUX,
	TI_CLKM_PLLSS,
	CLK_MAX_MEMMAPS
};


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