[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Barry Song]

this moves to generic IP module reset framework, and make other drivers
use common device_reset() API.

Cc: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Bin Shi <Bin.Shi@csr.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 -v4: fix checkpatch issues pointed out by Philipp;

 .../devicetree/bindings/reset/sirf,rstc.txt        |   42 ++++++++++
 arch/arm/boot/dts/atlas6.dtsi                      |    3 +-
 arch/arm/boot/dts/marco.dtsi                       |    3 +-
 arch/arm/boot/dts/prima2.dtsi                      |    3 +-
 arch/arm/mach-prima2/Kconfig                       |    1 +
 arch/arm/mach-prima2/common.c                      |   12 +++-
 arch/arm/mach-prima2/common.h                      |    1 +
 arch/arm/mach-prima2/rstc.c                        |   80 +++++++++++--------
 8 files changed, 107 insertions(+), 38 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/reset/sirf,rstc.txt

diff --git a/Documentation/devicetree/bindings/reset/sirf,rstc.txt b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
new file mode 100644
index 0000000..0505de7
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
@@ -0,0 +1,42 @@
+CSR SiRFSoC Reset Controller
+======================================
+
+Please also refer to reset.txt in this directory for common reset
+controller binding usage.
+
+Required properties:
+- compatible: Should be "sirf,prima2-rstc" or "sirf,marco-rstc"
+- reg: should be register base and length as documented in the
+  datasheet
+- #reset-cells: 1, see below
+
+example:
+
+rstc: reset-controller at 88010000 {
+	compatible = "sirf,prima2-rstc";
+	reg = <0x88010000 0x1000>;
+	#reset-cells = <1>;
+};
+
+Specifying reset lines connected to IP modules
+==============================================
+
+The reset controller(rstc) manages various reset sources. This module provides
+reset signals for most blocks in system. Those device nodes should specify the
+reset line on the rstc in their resets property, containing a phandle to the
+rstc device node and a RESET_INDEX specifying which module to reset, as described
+in reset.txt.
+
+For SiRFSoC, RESET_INDEX is just reset_bit defined in SW_RST0 and SW_RST1 registers.
+For modules whose rest_bit is in SW_RST0, its RESET_INDEX is 0~31. For modules whose
+rest_bit is in SW_RST1, its RESET_INDEX is 32~63.
+
+example:
+
+vpp at 90020000 {
+	compatible = "sirf,prima2-vpp";
+	reg = <0x90020000 0x10000>;
+	interrupts = <31>;
+	clocks = <&clks 35>;
+	resets = <&rstc 6>;
+};
diff --git a/arch/arm/boot/dts/atlas6.dtsi b/arch/arm/boot/dts/atlas6.dtsi
index 978bab4..b63cfef 100644
--- a/arch/arm/boot/dts/atlas6.dtsi
+++ b/arch/arm/boot/dts/atlas6.dtsi
@@ -56,9 +56,10 @@
 				#clock-cells = <1>;
 			};
 
-			reset-controller at 88010000 {
+			rstc: reset-controller at 88010000 {
 				compatible = "sirf,prima2-rstc";
 				reg = <0x88010000 0x1000>;
+				#reset-cells = <1>;
 			};
 
 			rsc-controller at 88020000 {
diff --git a/arch/arm/boot/dts/marco.dtsi b/arch/arm/boot/dts/marco.dtsi
index 1579c34..0c9647d 100644
--- a/arch/arm/boot/dts/marco.dtsi
+++ b/arch/arm/boot/dts/marco.dtsi
@@ -58,9 +58,10 @@
 			#size-cells = <1>;
 			ranges = <0xc2000000 0xc2000000 0x1000000>;
 
-			reset-controller at c2000000 {
+			rstc: reset-controller at c2000000 {
 				compatible = "sirf,marco-rstc";
 				reg = <0xc2000000 0x10000>;
+				#reset-cells = <1>;
 			};
 		};
 
diff --git a/arch/arm/boot/dts/prima2.dtsi b/arch/arm/boot/dts/prima2.dtsi
index daee5894..b292a5c 100644
--- a/arch/arm/boot/dts/prima2.dtsi
+++ b/arch/arm/boot/dts/prima2.dtsi
@@ -67,9 +67,10 @@
 				#clock-cells = <1>;
 			};
 
-			reset-controller at 88010000 {
+			rstc: reset-controller at 88010000 {
 				compatible = "sirf,prima2-rstc";
 				reg = <0x88010000 0x1000>;
+				#reset-cells = <1>;
 			};
 
 			rsc-controller at 88020000 {
diff --git a/arch/arm/mach-prima2/Kconfig b/arch/arm/mach-prima2/Kconfig
index 6988b11..f37a1de 100644
--- a/arch/arm/mach-prima2/Kconfig
+++ b/arch/arm/mach-prima2/Kconfig
@@ -1,5 +1,6 @@
 config ARCH_SIRF
 	bool "CSR SiRF" if ARCH_MULTI_V7
+	select ARCH_HAS_RESET_CONTROLLER
 	select ARCH_REQUIRE_GPIOLIB
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_IRQ_CHIP
diff --git a/arch/arm/mach-prima2/common.c b/arch/arm/mach-prima2/common.c
index d49aff7..4a14ae7 100644
--- a/arch/arm/mach-prima2/common.c
+++ b/arch/arm/mach-prima2/common.c
@@ -15,7 +15,14 @@
 #include <linux/of_platform.h>
 #include "common.h"
 
-void __init sirfsoc_init_late(void)
+static void __init sirfsoc_init_mach(void)
+{
+	sirfsoc_of_rstc_init();
+	of_platform_populate(NULL, of_default_bus_match_table,
+		NULL, NULL);
+}
+
+static void __init sirfsoc_init_late(void)
 {
 	sirfsoc_pm_init();
 }
@@ -35,6 +42,7 @@ static const char *atlas6_dt_match[] __initdata = {
 DT_MACHINE_START(ATLAS6_DT, "Generic ATLAS6 (Flattened Device Tree)")
 	/* Maintainer: Barry Song <baohua.song@csr.com> */
 	.map_io         = sirfsoc_map_io,
+	.init_machine   = sirfsoc_init_mach,
 	.init_late	= sirfsoc_init_late,
 	.dt_compat      = atlas6_dt_match,
 	.restart	= sirfsoc_restart,
@@ -51,6 +59,7 @@ DT_MACHINE_START(PRIMA2_DT, "Generic PRIMA2 (Flattened Device Tree)")
 	/* Maintainer: Barry Song <baohua.song@csr.com> */
 	.map_io         = sirfsoc_map_io,
 	.dma_zone_size	= SZ_256M,
+	.init_machine   = sirfsoc_init_mach,
 	.init_late	= sirfsoc_init_late,
 	.dt_compat      = prima2_dt_match,
 	.restart	= sirfsoc_restart,
@@ -67,6 +76,7 @@ DT_MACHINE_START(MARCO_DT, "Generic MARCO (Flattened Device Tree)")
 	/* Maintainer: Barry Song <baohua.song@csr.com> */
 	.smp            = smp_ops(sirfsoc_smp_ops),
 	.map_io         = sirfsoc_map_io,
+	.init_machine   = sirfsoc_init_mach,
 	.init_late	= sirfsoc_init_late,
 	.dt_compat      = marco_dt_match,
 	.restart	= sirfsoc_restart,
diff --git a/arch/arm/mach-prima2/common.h b/arch/arm/mach-prima2/common.h
index 4b76806..0896efd 100644
--- a/arch/arm/mach-prima2/common.h
+++ b/arch/arm/mach-prima2/common.h
@@ -22,6 +22,7 @@ extern struct smp_operations   sirfsoc_smp_ops;
 extern void sirfsoc_secondary_startup(void);
 extern void sirfsoc_cpu_die(unsigned int cpu);
 
+extern void __init sirfsoc_of_rstc_init(void);
 extern void __init sirfsoc_of_irq_init(void);
 extern void sirfsoc_restart(enum reboot_mode, const char *);
 extern asmlinkage void __exception_irq_entry sirfsoc_handle_irq(struct pt_regs *regs);
diff --git a/arch/arm/mach-prima2/rstc.c b/arch/arm/mach-prima2/rstc.c
index ccb5339..d2d777f 100644
--- a/arch/arm/mach-prima2/rstc.c
+++ b/arch/arm/mach-prima2/rstc.c
@@ -14,56 +14,34 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/reboot.h>
+#include <linux/reset-controller.h>
+
+#define SIRFSOC_RSTBIT_NUM	64
 
 void __iomem *sirfsoc_rstc_base;
 static DEFINE_MUTEX(rstc_lock);
 
-static struct of_device_id rstc_ids[]  = {
-	{ .compatible = "sirf,prima2-rstc" },
-	{ .compatible = "sirf,marco-rstc" },
-	{},
-};
-
-static int __init sirfsoc_of_rstc_init(void)
-{
-	struct device_node *np;
-
-	np = of_find_matching_node(NULL, rstc_ids);
-	if (!np) {
-		pr_err("unable to find compatible sirf rstc node in dtb\n");
-		return -ENOENT;
-	}
-
-	sirfsoc_rstc_base = of_iomap(np, 0);
-	if (!sirfsoc_rstc_base)
-		panic("unable to map rstc cpu registers\n");
-
-	of_node_put(np);
-
-	return 0;
-}
-early_initcall(sirfsoc_of_rstc_init);
-
-int sirfsoc_reset_device(struct device *dev)
+static int sirfsoc_reset_module(struct reset_controller_dev *rcdev,
+					unsigned long sw_reset_idx)
 {
-	u32 reset_bit;
+	u32 reset_bit = sw_reset_idx;
 
-	if (of_property_read_u32(dev->of_node, "reset-bit", &reset_bit))
+	if (reset_bit >= SIRFSOC_RSTBIT_NUM)
 		return -EINVAL;
 
 	mutex_lock(&rstc_lock);
 
-	if (of_device_is_compatible(dev->of_node, "sirf,prima2-rstc")) {
+	if (of_device_is_compatible(rcdev->of_node, "sirf,prima2-rstc")) {
 		/*
 		 * Writing 1 to this bit resets corresponding block. Writing 0 to this
 		 * bit de-asserts reset signal of the corresponding block.
 		 * datasheet doesn't require explicit delay between the set and clear
 		 * of reset bit. it could be shorter if tests pass.
 		 */
-		writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) | reset_bit,
+		writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) | (1 << reset_bit),
 			sirfsoc_rstc_base + (reset_bit / 32) * 4);
 		msleep(10);
-		writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) & ~reset_bit,
+		writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) & ~(1 << reset_bit),
 			sirfsoc_rstc_base + (reset_bit / 32) * 4);
 	} else {
 		/*
@@ -73,9 +51,9 @@ int sirfsoc_reset_device(struct device *dev)
 		 * datasheet doesn't require explicit delay between the set and clear
 		 * of reset bit. it could be shorter if tests pass.
 		 */
-		writel(reset_bit, sirfsoc_rstc_base + (reset_bit / 32) * 8);
+		writel(1 << reset_bit, sirfsoc_rstc_base + (reset_bit / 32) * 8);
 		msleep(10);
-		writel(reset_bit, sirfsoc_rstc_base + (reset_bit / 32) * 8 + 4);
+		writel(1 << reset_bit, sirfsoc_rstc_base + (reset_bit / 32) * 8 + 4);
 	}
 
 	mutex_unlock(&rstc_lock);
@@ -83,6 +61,40 @@ int sirfsoc_reset_device(struct device *dev)
 	return 0;
 }
 
+static struct reset_control_ops sirfsoc_rstc_ops = {
+	.reset = sirfsoc_reset_module,
+};
+
+static struct reset_controller_dev sirfsoc_reset_controller = {
+	.ops = &sirfsoc_rstc_ops,
+	.nr_resets = SIRFSOC_RSTBIT_NUM,
+};
+
+static struct of_device_id rstc_ids[]  = {
+	{ .compatible = "sirf,prima2-rstc" },
+	{ .compatible = "sirf,marco-rstc" },
+	{},
+};
+
+void __init sirfsoc_of_rstc_init(void)
+{
+	struct device_node *np = of_find_matching_node(NULL, rstc_ids);
+	if (!np) {
+		pr_err("unable to find compatible sirf rstc node in dtb\n");
+		return;
+	}
+
+	sirfsoc_rstc_base = of_iomap(np, 0);
+	if (!sirfsoc_rstc_base) {
+		pr_err("unable to map rstc cpu registers\n");
+		return;
+	}
+
+	sirfsoc_reset_controller.of_node = np;
+
+	reset_controller_register(&sirfsoc_reset_controller);
+}
+
 #define SIRFSOC_SYS_RST_BIT  BIT(31)
 
 void sirfsoc_restart(enum reboot_mode mode, const char *cmd)
-- 
1.7.5.4

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Arnd Bergmann]

On Monday 06 January 2014, Barry Song wrote:
> this moves to generic IP module reset framework, and make other drivers
> use common device_reset() API.
> 
> diff --git a/Documentation/devicetree/bindings/reset/sirf,rstc.txt b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
> new file mode 100644
> index 0000000..0505de7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
> @@ -0,0 +1,42 @@
> +CSR SiRFSoC Reset Controller
> +======================================
> +
> +Please also refer to reset.txt in this directory for common reset
> +controller binding usage.
> +
> +Required properties:
> +- compatible: Should be "sirf,prima2-rstc" or "sirf,marco-rstc"
> +- reg: should be register base and length as documented in the
> +  datasheet
> +- #reset-cells: 1, see below
> +
> +example:
> +
> +rstc: reset-controller at 88010000 {
> +	compatible = "sirf,prima2-rstc";
> +	reg = <0x88010000 0x1000>;
> +	#reset-cells = <1>;
> +};

Binding looks good to me.

> +void __init sirfsoc_of_rstc_init(void)
> +{
> +	struct device_node *np = of_find_matching_node(NULL, rstc_ids);
> +	if (!np) {
> +		pr_err("unable to find compatible sirf rstc node in dtb\n");
> +		return;
> +	}
> +
> +	sirfsoc_rstc_base = of_iomap(np, 0);
> +	if (!sirfsoc_rstc_base) {
> +		pr_err("unable to map rstc cpu registers\n");
> +		return;
> +	}
> +
> +	sirfsoc_reset_controller.of_node = np;
> +
> +	reset_controller_register(&sirfsoc_reset_controller);
> +}
> +

Can't this be a regular platform device? Drivers that get the reference to
the reset controller should respect a -EPROBE_DEFER error message if they
get initialized in the wrong order.

	Arnd

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Barry Song]

2014/1/6 Arnd Bergmann <arnd@arndb.de>:
> On Monday 06 January 2014, Barry Song wrote:
>> this moves to generic IP module reset framework, and make other drivers
>> use common device_reset() API.
>>
>> diff --git a/Documentation/devicetree/bindings/reset/sirf,rstc.txt b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
>> new file mode 100644
>> index 0000000..0505de7
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/reset/sirf,rstc.txt
>> @@ -0,0 +1,42 @@
>> +CSR SiRFSoC Reset Controller
>> +======================================
>> +
>> +Please also refer to reset.txt in this directory for common reset
>> +controller binding usage.
>> +
>> +Required properties:
>> +- compatible: Should be "sirf,prima2-rstc" or "sirf,marco-rstc"
>> +- reg: should be register base and length as documented in the
>> +  datasheet
>> +- #reset-cells: 1, see below
>> +
>> +example:
>> +
>> +rstc: reset-controller at 88010000 {
>> +     compatible = "sirf,prima2-rstc";
>> +     reg = <0x88010000 0x1000>;
>> +     #reset-cells = <1>;
>> +};
>
> Binding looks good to me.
>
>> +void __init sirfsoc_of_rstc_init(void)
>> +{
>> +     struct device_node *np = of_find_matching_node(NULL, rstc_ids);
>> +     if (!np) {
>> +             pr_err("unable to find compatible sirf rstc node in dtb\n");
>> +             return;
>> +     }
>> +
>> +     sirfsoc_rstc_base = of_iomap(np, 0);
>> +     if (!sirfsoc_rstc_base) {
>> +             pr_err("unable to map rstc cpu registers\n");
>> +             return;
>> +     }
>> +
>> +     sirfsoc_reset_controller.of_node = np;
>> +
>> +     reset_controller_register(&sirfsoc_reset_controller);
>> +}
>> +
>
> Can't this be a regular platform device? Drivers that get the reference to
> the reset controller should respect a -EPROBE_DEFER error message if they
> get initialized in the wrong order.

Arnd, it is ok if prima2 is not a platform for automotive. here prima2
actually wants a "right" order for products.
for example, there are some local hacking to move camera for rearview
started earlier than other devices as this feature needs to be ready
as early as possible.
some earlier boot devices depend on reset module to be ready. so if we
move to regular platform driver for upstream, it still requires some
local hacking to move it earlier.

>
>         Arnd

-barry

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Arnd Bergmann]

On Tuesday 07 January 2014, Barry Song wrote:
> 2014/1/6 Arnd Bergmann <arnd@arndb.de>:
> > On Monday 06 January 2014, Barry Song wrote:
> >
> >> +void __init sirfsoc_of_rstc_init(void)
> >> +{
> >> +     struct device_node *np = of_find_matching_node(NULL, rstc_ids);
> >> +     if (!np) {
> >> +             pr_err("unable to find compatible sirf rstc node in dtb\n");
> >> +             return;
> >> +     }
> >> +
> >> +     sirfsoc_rstc_base = of_iomap(np, 0);
> >> +     if (!sirfsoc_rstc_base) {
> >> +             pr_err("unable to map rstc cpu registers\n");
> >> +             return;
> >> +     }
> >> +
> >> +     sirfsoc_reset_controller.of_node = np;
> >> +
> >> +     reset_controller_register(&sirfsoc_reset_controller);
> >> +}
> >> +
> >
> > Can't this be a regular platform device? Drivers that get the reference to
> > the reset controller should respect a -EPROBE_DEFER error message if they
> > get initialized in the wrong order.
> 
> Arnd, it is ok if prima2 is not a platform for automotive. here prima2
> actually wants a "right" order for products.
> for example, there are some local hacking to move camera for rearview
> started earlier than other devices as this feature needs to be ready
> as early as possible.
> some earlier boot devices depend on reset module to be ready. so if we
> move to regular platform driver for upstream, it still requires some
> local hacking to move it earlier.

I don't understand what you mean. It should be a matter of a few miliseconds
at most to retry initialization, more likely in the microseconds. How big
are the delays you are worried about?

	Arnd

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Barry Song]

2014/1/7 Arnd Bergmann <arnd@arndb.de>:
> On Tuesday 07 January 2014, Barry Song wrote:
>> 2014/1/6 Arnd Bergmann <arnd@arndb.de>:
>> > On Monday 06 January 2014, Barry Song wrote:
>> >
>> >> +void __init sirfsoc_of_rstc_init(void)
>> >> +{
>> >> +     struct device_node *np = of_find_matching_node(NULL, rstc_ids);
>> >> +     if (!np) {
>> >> +             pr_err("unable to find compatible sirf rstc node in dtb\n");
>> >> +             return;
>> >> +     }
>> >> +
>> >> +     sirfsoc_rstc_base = of_iomap(np, 0);
>> >> +     if (!sirfsoc_rstc_base) {
>> >> +             pr_err("unable to map rstc cpu registers\n");
>> >> +             return;
>> >> +     }
>> >> +
>> >> +     sirfsoc_reset_controller.of_node = np;
>> >> +
>> >> +     reset_controller_register(&sirfsoc_reset_controller);
>> >> +}
>> >> +
>> >
>> > Can't this be a regular platform device? Drivers that get the reference to
>> > the reset controller should respect a -EPROBE_DEFER error message if they
>> > get initialized in the wrong order.
>>
>> Arnd, it is ok if prima2 is not a platform for automotive. here prima2
>> actually wants a "right" order for products.
>> for example, there are some local hacking to move camera for rearview
>> started earlier than other devices as this feature needs to be ready
>> as early as possible.
>> some earlier boot devices depend on reset module to be ready. so if we
>> move to regular platform driver for upstream, it still requires some
>> local hacking to move it earlier.
>
> I don't understand what you mean. It should be a matter of a few miliseconds
> at most to retry initialization, more likely in the microseconds. How big
> are the delays you are worried about?

what i am worrried about is 100ms or more. device drivers need time to
initialize and that will take time, if some devices initialization
happen before the deferred probing, the deferred probing might be
delayed 100ms.
for example, we want camera begin to show rear-view in several
hundreds of ms, there are some local hacking to move i2c and camera
probe earlier than other devices.
that means actually there is requirement for right order of probing
but not defer probing sometimes.

>
>         Arnd

-barry

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Arnd Bergmann]

On Thursday 09 January 2014, Barry Song wrote:
> 2014/1/7 Arnd Bergmann <arnd@arndb.de>:
> > On Tuesday 07 January 2014, Barry Song wrote:
> >> > Can't this be a regular platform device? Drivers that get the reference to
> >> > the reset controller should respect a -EPROBE_DEFER error message if they
> >> > get initialized in the wrong order.
> >>
> >> Arnd, it is ok if prima2 is not a platform for automotive. here prima2
> >> actually wants a "right" order for products.
> >> for example, there are some local hacking to move camera for rearview
> >> started earlier than other devices as this feature needs to be ready
> >> as early as possible.
> >> some earlier boot devices depend on reset module to be ready. so if we
> >> move to regular platform driver for upstream, it still requires some
> >> local hacking to move it earlier.
> >
> > I don't understand what you mean. It should be a matter of a few miliseconds
> > at most to retry initialization, more likely in the microseconds. How big
> > are the delays you are worried about?
> 
> what i am worrried about is 100ms or more. device drivers need time to
> initialize and that will take time, if some devices initialization
> happen before the deferred probing, the deferred probing might be
> delayed 100ms.
> for example, we want camera begin to show rear-view in several
> hundreds of ms, there are some local hacking to move i2c and camera
> probe earlier than other devices.
> that means actually there is requirement for right order of probing
> but not defer probing sometimes.

I see, this seems like a valid concern. I had not considered that other
drivers might need more time for initialization. In general of course
they should not, but I understand that hardware is not perfect and
some drivers you don't own may have bugs that cause unnecessary delays.

We have discussed probe ordering a lot of times on the mailing lists
and also during the last kernel summit, but those discussions are usually
focused on trying to correctly boot up a system, which is hard enough
even without additional requirements like yours.

Generally the hack that people use when things fail to work correctly
is to hijack an earlier initcall level, e.g. subsys_initcall rather
than using module_init. Please first see if that can solve your problem.
If it doesn't help, please resubmit your current patch with a detailed
description in the code on why you have to do it like this.

	Arnd

[PATCH v4] ARM: prima2: move to generic reset controller driver framework

[Barry Song]

2014/1/9 Arnd Bergmann <arnd@arndb.de>:
> On Thursday 09 January 2014, Barry Song wrote:
>> 2014/1/7 Arnd Bergmann <arnd@arndb.de>:
>> > On Tuesday 07 January 2014, Barry Song wrote:
>> >> > Can't this be a regular platform device? Drivers that get the reference to
>> >> > the reset controller should respect a -EPROBE_DEFER error message if they
>> >> > get initialized in the wrong order.
>> >>
>> >> Arnd, it is ok if prima2 is not a platform for automotive. here prima2
>> >> actually wants a "right" order for products.
>> >> for example, there are some local hacking to move camera for rearview
>> >> started earlier than other devices as this feature needs to be ready
>> >> as early as possible.
>> >> some earlier boot devices depend on reset module to be ready. so if we
>> >> move to regular platform driver for upstream, it still requires some
>> >> local hacking to move it earlier.
>> >
>> > I don't understand what you mean. It should be a matter of a few miliseconds
>> > at most to retry initialization, more likely in the microseconds. How big
>> > are the delays you are worried about?
>>
>> what i am worrried about is 100ms or more. device drivers need time to
>> initialize and that will take time, if some devices initialization
>> happen before the deferred probing, the deferred probing might be
>> delayed 100ms.
>> for example, we want camera begin to show rear-view in several
>> hundreds of ms, there are some local hacking to move i2c and camera
>> probe earlier than other devices.
>> that means actually there is requirement for right order of probing
>> but not defer probing sometimes.
>
> I see, this seems like a valid concern. I had not considered that other
> drivers might need more time for initialization. In general of course
> they should not, but I understand that hardware is not perfect and
> some drivers you don't own may have bugs that cause unnecessary delays.

the functionality of defer probing is really working. but embedded
systems with all kinds of hardware and various strange requirement
will want the "right" order.

>
> We have discussed probe ordering a lot of times on the mailing lists
> and also during the last kernel summit, but those discussions are usually
> focused on trying to correctly boot up a system, which is hard enough
> even without additional requirements like yours.
>
> Generally the hack that people use when things fail to work correctly
> is to hijack an earlier initcall level, e.g. subsys_initcall rather
> than using module_init. Please first see if that can solve your problem.
> If it doesn't help, please resubmit your current patch with a detailed
> description in the code on why you have to do it like this.

that is ok if it moves to subsys_initcall. some people might think
using subsys_initcall imports redundant function call for non-sirf
platform in multi-platform and machine-specific hook will not import
that :-)

>
>         Arnd

-barry