[RFC,3/4] powerpc: refactor of_get_cpu_node to support other architectures

Commit Message

Sudeep KarkadaNagesha Aug. 15, 2013, 5:09 p.m. UTC

From: Sudeep KarkadaNagesha <[e-mail]>

Currently different drivers requiring to access cpu device node are
parsing the device tree themselves. Since the ordering in the DT need
not match the logical cpu ordering, the parsing logic needs to consider
that. However, this has resulted in lots of code duplication and in some
cases even incorrect logic.

It's better to consolidate them by adding support for getting cpu
device node for a given logical cpu index in DT core library. However
logical to physical index mapping can be architecture specific.

PowerPC has it's own implementation to get the cpu node for a given
logical index.

This patch refactors the current implementation of of_get_cpu_node.
This in preparation to move the implementation to DT core library.
It separates out the logical to physical mapping so that a default
matching of the physical id to the logical cpu index can be added
when moved to common code. Architecture specific code can override it.

Cc: Rob Herring <[e-mail]>
Cc: Grant Likely <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Signed-off-by: Sudeep KarkadaNagesha <[e-mail]>
---
 arch/powerpc/kernel/prom.c | 70 ++++++++++++++++++++++++++++------------------
 1 file changed, 43 insertions(+), 27 deletions(-)

Comments

Benjamin Herrenschmidt Aug. 16, 2013, 4:49 a.m. UTC | #1

On Thu, 2013-08-15 at 18:09 +0100, Sudeep KarkadaNagesha wrote:
> From: Sudeep KarkadaNagesha <[e-mail]>
> 
> Currently different drivers requiring to access cpu device node are
> parsing the device tree themselves. Since the ordering in the DT need
> not match the logical cpu ordering, the parsing logic needs to consider
> that. However, this has resulted in lots of code duplication and in some
> cases even incorrect logic.

 .../...

>  
> +bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
> +{
> +	return (int)phys_id == get_hard_smp_processor_id(cpu);
> +}

Naming is a bit gross. You might want to make it clearer that
we are talking about CPU IDs in the device-tree here.

> +static bool __of_find_n_match_cpu_property(struct device_node *cpun,
> +			const char *prop_name, int cpu, unsigned int *thread)
> +{
> +	const __be32 *cell;
> +	int ac, prop_len, tid;
> +	u64 hwid;
> +
> +	ac = of_n_addr_cells(cpun);
> +	cell = of_get_property(cpun, prop_name, &prop_len);
> +	if (!cell)
> +		return false;
> +	prop_len /= sizeof(*cell);
> +	for (tid = 0; tid < prop_len; tid++) {
> +		hwid = of_read_number(cell, ac);
> +		if (arch_match_cpu_phys_id(cpu, hwid)) {
> +			if (thread)
> +				*thread = tid;
> +			return true;
> +		}

Missing:          cell += ac;

> +	}
> +	return false;
> +}
> +
>  /* Find the device node for a given logical cpu number, also returns the cpu
>   * local thread number (index in ibm,interrupt-server#s) if relevant and
>   * asked for (non NULL)
>   */
>  struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
>  {
> -	int hardid;
> -	struct device_node *np;
> +	struct device_node *cpun, *cpus;
>  
> -	hardid = get_hard_smp_processor_id(cpu);
> +	cpus = of_find_node_by_path("/cpus");
> +	if (!cpus) {
> +		pr_warn("Missing cpus node, bailing out\n");
> +		return NULL;
> +	}
>  
> -	for_each_node_by_type(np, "cpu") {
> -		const u32 *intserv;
> -		unsigned int plen, t;
> +	for_each_child_of_node(cpus, cpun) {
> +		if (of_node_cmp(cpun->type, "cpu"))
> +			continue;
>  
>  		/* Check for ibm,ppc-interrupt-server#s. If it doesn't exist
>  		 * fallback to "reg" property and assume no threads
>  		 */
> -		intserv = of_get_property(np, "ibm,ppc-interrupt-server#s",
> -				&plen);
> -		if (intserv == NULL) {
> -			const u32 *reg = of_get_property(np, "reg", NULL);
> -			if (reg == NULL)
> -				continue;
> -			if (*reg == hardid) {
> -				if (thread)
> -					*thread = 0;
> -				return np;
> -			}
> -		} else {
> -			plen /= sizeof(u32);
> -			for (t = 0; t < plen; t++) {
> -				if (hardid == intserv[t]) {
> -					if (thread)
> -						*thread = t;
> -					return np;
> -				}
> -			}
> -		}
> +		if (__of_find_n_match_cpu_property(cpun,
> +				"ibm,ppc-interrupt-server#s", cpu, thread))
> +			return cpun;
> +
> +		if (__of_find_n_match_cpu_property(cpun, "reg", cpu, thread))
> +			return cpun;
>  	}
>  	return NULL;
>  }

Cheers,
Ben.


--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Benjamin Herrenschmidt Aug. 16, 2013, 4:50 a.m. UTC | #2

On Thu, 2013-08-15 at 18:09 +0100, Sudeep KarkadaNagesha wrote:
>                /* Check for ibm,ppc-interrupt-server#s. If it doesn't exist
>                  * fallback to "reg" property and assume no threads
>                  */
> -

Oh and I forgot ... that comment is now wrong, since your code handles
threads in the "reg" case...

Cheers,
Ben.


--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Sudeep KarkadaNagesha Aug. 16, 2013, 8:43 a.m. UTC | #3

On 16/08/13 05:50, Benjamin Herrenschmidt wrote:
> On Thu, 2013-08-15 at 18:09 +0100, Sudeep KarkadaNagesha wrote:
>>                /* Check for ibm,ppc-interrupt-server#s. If it doesn't exist
>>                  * fallback to "reg" property and assume no threads
>>                  */
>> -
> 
> Oh and I forgot ... that comment is now wrong, since your code handles
> threads in the "reg" case...
> 
I have fixed it in the next patch while adding the documentation to
these function. I wanted changes in this patch minimal. I can fix it
here too if you insist on it.

Regards,
Sudeep


--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Sudeep KarkadaNagesha Aug. 16, 2013, 8:48 a.m. UTC | #4

On 16/08/13 05:49, Benjamin Herrenschmidt wrote:
> On Thu, 2013-08-15 at 18:09 +0100, Sudeep KarkadaNagesha wrote:
>> From: Sudeep KarkadaNagesha <[e-mail]>
>>
>> Currently different drivers requiring to access cpu device node are
>> parsing the device tree themselves. Since the ordering in the DT need
>> not match the logical cpu ordering, the parsing logic needs to consider
>> that. However, this has resulted in lots of code duplication and in some
>> cases even incorrect logic.
> 
>  .../...
> 
>>  
>> +bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
>> +{
>> +	return (int)phys_id == get_hard_smp_processor_id(cpu);
>> +}
> 
> Naming is a bit gross. You might want to make it clearer that
> we are talking about CPU IDs in the device-tree here.
> 
Any particular preference to the name or just a note is sufficient.
Also unlike PPC, in ARM we don't set hard processor id value based
values read from device tree. DT must contain the values matching to the
hardware ID registers.

>> +static bool __of_find_n_match_cpu_property(struct device_node *cpun,
>> +			const char *prop_name, int cpu, unsigned int *thread)
>> +{
>> +	const __be32 *cell;
>> +	int ac, prop_len, tid;
>> +	u64 hwid;
>> +
>> +	ac = of_n_addr_cells(cpun);
>> +	cell = of_get_property(cpun, prop_name, &prop_len);
>> +	if (!cell)
>> +		return false;
>> +	prop_len /= sizeof(*cell);
>> +	for (tid = 0; tid < prop_len; tid++) {
>> +		hwid = of_read_number(cell, ac);
>> +		if (arch_match_cpu_phys_id(cpu, hwid)) {
>> +			if (thread)
>> +				*thread = tid;
>> +			return true;
>> +		}
> 
> Missing:          cell += ac;
Ah, missed it while refactoring, will fix it. Thanks

Regards,
Sudeep




--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Benjamin Herrenschmidt Aug. 16, 2013, 12:32 p.m. UTC | #5

On Fri, 2013-08-16 at 09:48 +0100, Sudeep KarkadaNagesha wrote:

> > Naming is a bit gross. You might want to make it clearer that
> > we are talking about CPU IDs in the device-tree here.
> > 
> Any particular preference to the name or just a note is sufficient.
> Also unlike PPC, in ARM we don't set hard processor id value based
> values read from device tree. DT must contain the values matching to the
> hardware ID registers.

This is exactly the same on ppc. We don't "set" HW values. The
device-tree content matches the HW internals. Some processors have a
"PIR" register as well which contains the HW value, in this case the
device-tree must contain the same value as the PIR on that processor.

> >> +static bool __of_find_n_match_cpu_property(struct device_node *cpun,
> >> +			const char *prop_name, int cpu, unsigned int *thread)
> >> +{
> >> +	const __be32 *cell;
> >> +	int ac, prop_len, tid;
> >> +	u64 hwid;
> >> +
> >> +	ac = of_n_addr_cells(cpun);
> >> +	cell = of_get_property(cpun, prop_name, &prop_len);
> >> +	if (!cell)
> >> +		return false;
> >> +	prop_len /= sizeof(*cell);
> >> +	for (tid = 0; tid < prop_len; tid++) {
> >> +		hwid = of_read_number(cell, ac);
> >> +		if (arch_match_cpu_phys_id(cpu, hwid)) {
> >> +			if (thread)
> >> +				*thread = tid;
> >> +			return true;
> >> +		}
> > 
> > Missing:          cell += ac;
> Ah, missed it while refactoring, will fix it. Thanks

Ben.

> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [e-mail]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/


--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Sudeep KarkadaNagesha Aug. 16, 2013, 12:44 p.m. UTC | #6

On 16/08/13 13:32, Benjamin Herrenschmidt wrote:
> On Fri, 2013-08-16 at 09:48 +0100, Sudeep KarkadaNagesha wrote:
> 
>>> Naming is a bit gross. You might want to make it clearer that
>>> we are talking about CPU IDs in the device-tree here.
>>>
>> Any particular preference to the name or just a note is sufficient.
>> Also unlike PPC, in ARM we don't set hard processor id value based
>> values read from device tree. DT must contain the values matching to the
>> hardware ID registers.
> 
> This is exactly the same on ppc. We don't "set" HW values. The
> device-tree content matches the HW internals. Some processors have a
> "PIR" register as well which contains the HW value, in this case the
> device-tree must contain the same value as the PIR on that processor.
> 
Ok, I misread the function 'set_hard_smp_processor_id' function.
BTW, you didn't mention if you are OK by just have this clearly
documented in the function and/or you have any preference/better name.

I will send the next version based on that. I have even compile tested
:) now on PPC.

Regards,
Sudeep


--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index eb23ac9..594c9f9 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -865,45 +865,61 @@  static int __init prom_reconfig_setup(void)
 __initcall(prom_reconfig_setup);
 #endif
 
+bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
+{
+	return (int)phys_id == get_hard_smp_processor_id(cpu);
+}
+
+static bool __of_find_n_match_cpu_property(struct device_node *cpun,
+			const char *prop_name, int cpu, unsigned int *thread)
+{
+	const __be32 *cell;
+	int ac, prop_len, tid;
+	u64 hwid;
+
+	ac = of_n_addr_cells(cpun);
+	cell = of_get_property(cpun, prop_name, &prop_len);
+	if (!cell)
+		return false;
+	prop_len /= sizeof(*cell);
+	for (tid = 0; tid < prop_len; tid++) {
+		hwid = of_read_number(cell, ac);
+		if (arch_match_cpu_phys_id(cpu, hwid)) {
+			if (thread)
+				*thread = tid;
+			return true;
+		}
+	}
+	return false;
+}
+
 /* Find the device node for a given logical cpu number, also returns the cpu
  * local thread number (index in ibm,interrupt-server#s) if relevant and
  * asked for (non NULL)
  */
 struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
 {
-	int hardid;
-	struct device_node *np;
+	struct device_node *cpun, *cpus;
 
-	hardid = get_hard_smp_processor_id(cpu);
+	cpus = of_find_node_by_path("/cpus");
+	if (!cpus) {
+		pr_warn("Missing cpus node, bailing out\n");
+		return NULL;
+	}
 
-	for_each_node_by_type(np, "cpu") {
-		const u32 *intserv;
-		unsigned int plen, t;
+	for_each_child_of_node(cpus, cpun) {
+		if (of_node_cmp(cpun->type, "cpu"))
+			continue;
 
 		/* Check for ibm,ppc-interrupt-server#s. If it doesn't exist
 		 * fallback to "reg" property and assume no threads
 		 */
-		intserv = of_get_property(np, "ibm,ppc-interrupt-server#s",
-				&plen);
-		if (intserv == NULL) {
-			const u32 *reg = of_get_property(np, "reg", NULL);
-			if (reg == NULL)
-				continue;
-			if (*reg == hardid) {
-				if (thread)
-					*thread = 0;
-				return np;
-			}
-		} else {
-			plen /= sizeof(u32);
-			for (t = 0; t < plen; t++) {
-				if (hardid == intserv[t]) {
-					if (thread)
-						*thread = t;
-					return np;
-				}
-			}
-		}
+		if (__of_find_n_match_cpu_property(cpun,
+				"ibm,ppc-interrupt-server#s", cpu, thread))
+			return cpun;
+
+		if (__of_find_n_match_cpu_property(cpun, "reg", cpu, thread))
+			return cpun;
 	}
 	return NULL;
 }