Re: [RFC] ARM: OMAP: Remove nodes dynamically at runtime
Hi Rob, Thanks for the feedback. Some how our mail server appeared to filter out your response! On 06/21/2012 06:50 PM, Jon Hunter wrote: On 06/21/2012 02:15 PM, Jon Hunter wrote: Hi all, I am in the process of adding a device-tree binding for OMAP timers and I have encountered a scenario where ideally it would be useful to remove a device-tree node at runtime. The scenario is this ... 1. OMAP3 devices may or may not have security features enabled. Security enabled devices are known as high-secure (HS) and devices without security are known as general purpose (GP). 2. For OMAP3 devices there are 12 general purpose timers available. 3. On secure devices the 12th timer is reserved for secure usage and so cannot be used by the kernel, where as for a GP device it is available. 4. We can detect the OMAP device type, secure or GP, at runtime via an on-chip register. 5. Today, when not using DT, we do not register the 12th timer as a linux device if the device is secure. When migrating the timers to DT, I need a way to prevent this 12th timer from being registered as a device on a secure device. The options I have considered are ... a. Have separate a omap3.dtsi for GP and secure devices or place the node for the 12th timer in a omap3-gp.dtsi that is only used for boards with GP devices. The downside of this is that for boards that can support GP and secure device (such as the omap3 SDP) we require a separate dtb blob. That's certainly not ideal since you can distinguish which device you are on. Does omap have a custom register for this because determining secure vs. non-secure mode is a common problem without a standard way to determine it. Yes, unfortunately the register I was referring to is a custom OMAP register. b. Remove the timer node dynamically at runtime using the of_node_detach() API. In this solution we define a ti,timer-secure property that the 12th timer on omap3 devices would have and at runtime if we are a secure omap3 device, we search the timer nodes for any nodes with this property and remove them. Option B, seems to be the better option but requires me to enable CONFIG_OF_DYNAMIC for all omap devices and I was not sure if there is any downside to doing so. Enabling this feature does not seem to add much code as far as I can tell, however, I wanted to get some feedback before proposing this. Also if there are any other options I should consider then please let me know. I would wonder if of_node_get/put calls are all properly implemented. They don't really matter until OF_DYNAMIC is enabled, but it would affect all ARM DT platforms once we enable multi-platform support. Option C - have the bootloader set nodes status property to disabled. Option D - same as C, but do it in the kernel with prom_add_property. Option D, sounds good to me. I will look into this. Thanks Jon -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC] ARM: OMAP: Remove nodes dynamically at runtime
On 06/21/2012 06:50 PM, Jon Hunter wrote:
On 06/21/2012 02:15 PM, Jon Hunter wrote:
Hi all,
I am in the process of adding a device-tree binding for OMAP timers and
I have encountered a scenario where ideally it would be useful to remove
a device-tree node at runtime.
The scenario is this ...
1. OMAP3 devices may or may not have security features enabled. Security
enabled devices are known as high-secure (HS) and devices without
security are known as general purpose (GP).
2. For OMAP3 devices there are 12 general purpose timers available.
3. On secure devices the 12th timer is reserved for secure usage and so
cannot be used by the kernel, where as for a GP device it is available.
4. We can detect the OMAP device type, secure or GP, at runtime via an
on-chip register.
5. Today, when not using DT, we do not register the 12th timer as a linux
device if the device is secure.
When migrating the timers to DT, I need a way to prevent this 12th timer
from being registered as a device on a secure device. The options I have
considered are ...
a. Have separate a omap3.dtsi for GP and secure devices or place the
node for the 12th timer in a omap3-gp.dtsi that is only used for
boards with GP devices. The downside of this is that for boards
that can support GP and secure device (such as the omap3 SDP) we
require a separate dtb blob.
That's certainly not ideal since you can distinguish which device you
are on. Does omap have a custom register for this because determining
secure vs. non-secure mode is a common problem without a standard way to
determine it.
b. Remove the timer node dynamically at runtime using the
of_node_detach() API. In this solution we define a ti,timer-secure
property that the 12th timer on omap3 devices would have and at
runtime if we are a secure omap3 device, we search the timer nodes
for any nodes with this property and remove them.
Option B, seems to be the better option but requires me to enable
CONFIG_OF_DYNAMIC for all omap devices and I was not sure if there is any
downside to doing so. Enabling this feature does not seem to add much code
as far as I can tell, however, I wanted to get some feedback before
proposing this. Also if there are any other options I should consider then
please let me know.
I would wonder if of_node_get/put calls are all properly implemented.
They don't really matter until OF_DYNAMIC is enabled, but it would
affect all ARM DT platforms once we enable multi-platform support.
Option C - have the bootloader set nodes status property to disabled.
Option D - same as C, but do it in the kernel with prom_add_property.
Rob
For option B, the timer node would look like ...
+ timer12: timer@48304000 {
+ compatible = ti,omap3-timer;
+ ti,hwmods = timer12;
+ ti,timer-alwon;
+ ti,timer-secure;
+ };
I would then add the following function to the omap timer code to search
for any timers with the ti,timer-secure on a secure device and enable
the OF_DYNAMIC option. Right now it is only timer 12 on OMAP3 that
requires this, but I have made the function generic so that it could
handle other devices (but none exist today that I am aware of).
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index 8c22a8e..5e38946 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -36,6 +36,7 @@
#include linux/clocksource.h
#include linux/clockchips.h
#include linux/slab.h
+#include linux/of.h
#include asm/mach/time.h
#include plat/dmtimer.h
@@ -482,6 +483,35 @@ static int __init omap2_dm_timer_init(void)
}
arch_initcall(omap2_dm_timer_init);
+static struct of_device_id omap3_timer_match[] __initdata = {
+ { .compatible = ti,omap3-timer, },
+ { }
+};
+
+/**
+ * omap_dmtimer_init - initialisation function when device tree is used
+ *
+ * For secure OMAP3 devices, timers with property ti,timer-secure cannot
+ * be used by the kernel as they are reserved. Therefore, to prevent the
+ * kernel registering these devices remove them dynamically from the device
+ * tree on boot.
+ */
+void __init omap_dmtimer_init(void)
+{
+ struct device_node *np;
+
+ if (!cpu_is_omap34xx())
+ return;
+
+ /* If we are a secure device, remove any secure timer nodes */
+ if ((omap_type() == OMAP2_DEVICE_TYPE_GP)) {
Oops! Bug in the above code. Meant to be ...
if (omap_type() != OMAP2_DEVICE_TYPE_GP)
+ for_each_matching_node(np, omap3_timer_match) {
+ if (of_get_property(np, ti,timer-secure, NULL))
+ of_detach_node(np);
+ }
+ }
+}
Cheers
Jon
___
devicetree-discuss mailing list
devicetree-disc...@lists.ozlabs.org
Re: [RFC] ARM: OMAP: Remove nodes dynamically at runtime
Hi Rob, Grant,
Benoit suggested that I ask your opinion on the below.
Basically, I am trying to understand if there is any reason not to
enable OF_DYNAMIC. More details below on the exact scenario I am trying
to solve. OF_DYNAMIC seems to provide a good solution for me.
Thanks
Jon
On 06/21/2012 06:50 PM, Jon Hunter wrote:
On 06/21/2012 02:15 PM, Jon Hunter wrote:
Hi all,
I am in the process of adding a device-tree binding for OMAP timers and
I have encountered a scenario where ideally it would be useful to remove
a device-tree node at runtime.
The scenario is this ...
1. OMAP3 devices may or may not have security features enabled. Security
enabled devices are known as high-secure (HS) and devices without
security are known as general purpose (GP).
2. For OMAP3 devices there are 12 general purpose timers available.
3. On secure devices the 12th timer is reserved for secure usage and so
cannot be used by the kernel, where as for a GP device it is available.
4. We can detect the OMAP device type, secure or GP, at runtime via an
on-chip register.
5. Today, when not using DT, we do not register the 12th timer as a linux
device if the device is secure.
When migrating the timers to DT, I need a way to prevent this 12th timer
from being registered as a device on a secure device. The options I have
considered are ...
a. Have separate a omap3.dtsi for GP and secure devices or place the
node for the 12th timer in a omap3-gp.dtsi that is only used for
boards with GP devices. The downside of this is that for boards
that can support GP and secure device (such as the omap3 SDP) we
require a separate dtb blob.
b. Remove the timer node dynamically at runtime using the
of_node_detach() API. In this solution we define a ti,timer-secure
property that the 12th timer on omap3 devices would have and at
runtime if we are a secure omap3 device, we search the timer nodes
for any nodes with this property and remove them.
Option B, seems to be the better option but requires me to enable
CONFIG_OF_DYNAMIC for all omap devices and I was not sure if there is any
downside to doing so. Enabling this feature does not seem to add much code
as far as I can tell, however, I wanted to get some feedback before
proposing this. Also if there are any other options I should consider then
please let me know.
For option B, the timer node would look like ...
+ timer12: timer@48304000 {
+ compatible = ti,omap3-timer;
+ ti,hwmods = timer12;
+ ti,timer-alwon;
+ ti,timer-secure;
+ };
I would then add the following function to the omap timer code to search
for any timers with the ti,timer-secure on a secure device and enable
the OF_DYNAMIC option. Right now it is only timer 12 on OMAP3 that
requires this, but I have made the function generic so that it could
handle other devices (but none exist today that I am aware of).
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index 8c22a8e..5e38946 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -36,6 +36,7 @@
#include linux/clocksource.h
#include linux/clockchips.h
#include linux/slab.h
+#include linux/of.h
#include asm/mach/time.h
#include plat/dmtimer.h
@@ -482,6 +483,35 @@ static int __init omap2_dm_timer_init(void)
}
arch_initcall(omap2_dm_timer_init);
+static struct of_device_id omap3_timer_match[] __initdata = {
+ { .compatible = ti,omap3-timer, },
+ { }
+};
+
+/**
+ * omap_dmtimer_init - initialisation function when device tree is used
+ *
+ * For secure OMAP3 devices, timers with property ti,timer-secure cannot
+ * be used by the kernel as they are reserved. Therefore, to prevent the
+ * kernel registering these devices remove them dynamically from the device
+ * tree on boot.
+ */
+void __init omap_dmtimer_init(void)
+{
+ struct device_node *np;
+
+ if (!cpu_is_omap34xx())
+ return;
+
+ /* If we are a secure device, remove any secure timer nodes */
+ if ((omap_type() == OMAP2_DEVICE_TYPE_GP)) {
Oops! Bug in the above code. Meant to be ...
if (omap_type() != OMAP2_DEVICE_TYPE_GP)
+ for_each_matching_node(np, omap3_timer_match) {
+ if (of_get_property(np, ti,timer-secure, NULL))
+ of_detach_node(np);
+ }
+ }
+}
Cheers
Jon
--
To unsubscribe from this list: send the line unsubscribe linux-omap in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC] ARM: OMAP: Remove nodes dynamically at runtime
On 06/21/2012 02:15 PM, Jon Hunter wrote:
Hi all,
I am in the process of adding a device-tree binding for OMAP timers and
I have encountered a scenario where ideally it would be useful to remove
a device-tree node at runtime.
The scenario is this ...
1. OMAP3 devices may or may not have security features enabled. Security
enabled devices are known as high-secure (HS) and devices without
security are known as general purpose (GP).
2. For OMAP3 devices there are 12 general purpose timers available.
3. On secure devices the 12th timer is reserved for secure usage and so
cannot be used by the kernel, where as for a GP device it is available.
4. We can detect the OMAP device type, secure or GP, at runtime via an
on-chip register.
5. Today, when not using DT, we do not register the 12th timer as a linux
device if the device is secure.
When migrating the timers to DT, I need a way to prevent this 12th timer
from being registered as a device on a secure device. The options I have
considered are ...
a. Have separate a omap3.dtsi for GP and secure devices or place the
node for the 12th timer in a omap3-gp.dtsi that is only used for
boards with GP devices. The downside of this is that for boards
that can support GP and secure device (such as the omap3 SDP) we
require a separate dtb blob.
b. Remove the timer node dynamically at runtime using the
of_node_detach() API. In this solution we define a ti,timer-secure
property that the 12th timer on omap3 devices would have and at
runtime if we are a secure omap3 device, we search the timer nodes
for any nodes with this property and remove them.
Option B, seems to be the better option but requires me to enable
CONFIG_OF_DYNAMIC for all omap devices and I was not sure if there is any
downside to doing so. Enabling this feature does not seem to add much code
as far as I can tell, however, I wanted to get some feedback before
proposing this. Also if there are any other options I should consider then
please let me know.
For option B, the timer node would look like ...
+ timer12: timer@48304000 {
+ compatible = ti,omap3-timer;
+ ti,hwmods = timer12;
+ ti,timer-alwon;
+ ti,timer-secure;
+ };
I would then add the following function to the omap timer code to search
for any timers with the ti,timer-secure on a secure device and enable
the OF_DYNAMIC option. Right now it is only timer 12 on OMAP3 that
requires this, but I have made the function generic so that it could
handle other devices (but none exist today that I am aware of).
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index 8c22a8e..5e38946 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -36,6 +36,7 @@
#include linux/clocksource.h
#include linux/clockchips.h
#include linux/slab.h
+#include linux/of.h
#include asm/mach/time.h
#include plat/dmtimer.h
@@ -482,6 +483,35 @@ static int __init omap2_dm_timer_init(void)
}
arch_initcall(omap2_dm_timer_init);
+static struct of_device_id omap3_timer_match[] __initdata = {
+ { .compatible = ti,omap3-timer, },
+ { }
+};
+
+/**
+ * omap_dmtimer_init - initialisation function when device tree is used
+ *
+ * For secure OMAP3 devices, timers with property ti,timer-secure cannot
+ * be used by the kernel as they are reserved. Therefore, to prevent the
+ * kernel registering these devices remove them dynamically from the device
+ * tree on boot.
+ */
+void __init omap_dmtimer_init(void)
+{
+ struct device_node *np;
+
+ if (!cpu_is_omap34xx())
+ return;
+
+ /* If we are a secure device, remove any secure timer nodes */
+ if ((omap_type() == OMAP2_DEVICE_TYPE_GP)) {
Oops! Bug in the above code. Meant to be ...
if (omap_type() != OMAP2_DEVICE_TYPE_GP)
+ for_each_matching_node(np, omap3_timer_match) {
+ if (of_get_property(np, ti,timer-secure, NULL))
+ of_detach_node(np);
+ }
+ }
+}
Cheers
Jon
--
To unsubscribe from this list: send the line unsubscribe linux-omap in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
