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[PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes

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  [PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-09-14 22:10 +0200
    Re: [PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes Rob Herring <robh+dt@kernel.org> - 2016-09-15 15:50 +0200
      Re: [PATCH v2 1/3] drivers/of: recognize status property of dt  memory nodes Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-09-15 16:40 +0200
    Re: [PATCH v2 1/3] drivers/of: recognize status property of dt memory  nodes Balbir Singh <bsingharora@gmail.com> - 2016-09-19 12:20 +0200

#1483617 — [PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes

Respect the standard dt "status" property when scanning memory nodes in
early_init_dt_scan_memory(), so that if the property is present and not
"okay", no memory will be added.

The use case at hand is accelerator or device memory, which may be
unusable until post-boot initialization of the memory link. Such a node
can be described in the dt as any other, given its status is "disabled".
Per the device tree specification,

"disabled"
	Indicates that the device is not presently operational, but it
	might become operational in the future (for example, something
	is not plugged in, or switched off).

Once such memory is made operational, it can then be hotplugged.

Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
---
 drivers/of/fdt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 085c638..fc19590 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1022,8 +1022,10 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
 				     int depth, void *data)
 {
 	const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
+	const char *status;
 	const __be32 *reg, *endp;
 	int l;
+	bool add_memory;
 
 	/* We are scanning "memory" nodes only */
 	if (type == NULL) {
@@ -1044,6 +1046,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
 
 	endp = reg + (l / sizeof(__be32));
 
+	status = of_get_flat_dt_prop(node, "status", NULL);
+	add_memory = !status || !strcmp(status, "okay");
+
 	pr_debug("memory scan node %s, reg size %d,\n", uname, l);
 
 	while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
@@ -1057,6 +1062,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
 		pr_debug(" - %llx ,  %llx\n", (unsigned long long)base,
 		    (unsigned long long)size);
 
+		if (!add_memory)
+			continue;
+
 		early_init_dt_add_memory_arch(base, size);
 	}
 
-- 
1.8.3.1

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#1484182

On Wed, Sep 14, 2016 at 3:06 PM, Reza Arbab <arbab@linux.vnet.ibm.com> wrote:
> Respect the standard dt "status" property when scanning memory nodes in
> early_init_dt_scan_memory(), so that if the property is present and not
> "okay", no memory will be added.
>
> The use case at hand is accelerator or device memory, which may be
> unusable until post-boot initialization of the memory link. Such a node
> can be described in the dt as any other, given its status is "disabled".
> Per the device tree specification,
>
> "disabled"
>         Indicates that the device is not presently operational, but it
>         might become operational in the future (for example, something
>         is not plugged in, or switched off).
>
> Once such memory is made operational, it can then be hotplugged.
>
> Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
> ---
>  drivers/of/fdt.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 085c638..fc19590 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1022,8 +1022,10 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
>                                      int depth, void *data)
>  {
>         const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> +       const char *status;
>         const __be32 *reg, *endp;
>         int l;
> +       bool add_memory;
>
>         /* We are scanning "memory" nodes only */
>         if (type == NULL) {
> @@ -1044,6 +1046,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
>
>         endp = reg + (l / sizeof(__be32));
>
> +       status = of_get_flat_dt_prop(node, "status", NULL);
> +       add_memory = !status || !strcmp(status, "okay");

Move this into it's own function to mirror the unflattened version
(of_device_is_available). Also, make sure the logic is the same. IIRC,
"ok" is also allowed.

> +
>         pr_debug("memory scan node %s, reg size %d,\n", uname, l);
>
>         while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
> @@ -1057,6 +1062,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
>                 pr_debug(" - %llx ,  %llx\n", (unsigned long long)base,
>                     (unsigned long long)size);
>
> +               if (!add_memory)
> +                       continue;

There's no point in checking this in the loop. status applies to the
whole node. Just return up above.

Rob

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#1484230 — Re: [PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes

On Thu, Sep 15, 2016 at 08:43:08AM -0500, Rob Herring wrote:
>On Wed, Sep 14, 2016 at 3:06 PM, Reza Arbab <arbab@linux.vnet.ibm.com> wrote:
>> +       status = of_get_flat_dt_prop(node, "status", NULL);
>> +       add_memory = !status || !strcmp(status, "okay");
>
>Move this into it's own function to mirror the unflattened version
>(of_device_is_available). Also, make sure the logic is the same. IIRC,
>"ok" is also allowed.

Will do. 

>> @@ -1057,6 +1062,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
>>                 pr_debug(" - %llx ,  %llx\n", (unsigned long long)base,
>>                     (unsigned long long)size);
>>
>> +               if (!add_memory)
>> +                       continue;
>
>There's no point in checking this in the loop. status applies to the
>whole node. Just return up above.

I was trying to preserve that pr_debug output for these nodes, but I'm 
also fine with skipping it.

Thanks for your feedback! I'll spin a v3 of this patchset soon.

-- 
Reza Arbab

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#1486322 — Re: [PATCH v2 1/3] drivers/of: recognize status property of dt memory nodes

On 15/09/16 06:06, Reza Arbab wrote:
> Respect the standard dt "status" property when scanning memory nodes in
> early_init_dt_scan_memory(), so that if the property is present and not
> "okay", no memory will be added.
> 
> The use case at hand is accelerator or device memory, which may be
> unusable until post-boot initialization of the memory link. Such a node
> can be described in the dt as any other, given its status is "disabled".
> Per the device tree specification,
> 
> "disabled"
> 	Indicates that the device is not presently operational, but it
> 	might become operational in the future (for example, something
> 	is not plugged in, or switched off).
> 
> Once such memory is made operational, it can then be hotplugged.
> 
> Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>

Makes sense, so basically a /memory@  with missing status or status = "okay"
are added, others are skipped. No memblocks corresponding to those nodes
are created either.

Balbir Singh

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