[PATCH V3] cxl: Fix timebase synchronization status on P9

[PATCH V3] cxl: Fix timebase synchronization status on P9

[Christophe Lombard]

The PSL Timebase register is updated by the PSL to maintain the
timebase.
On P9, the Timebase value is only provided by the CAPP as received
the last time a timebase request was performed.
The timebase requests are initiated through the adapter configuration or
application registers.
The specific sysfs entry "/sys/class/cxl/cardxx/psl_timebase_synced" is
now dynamically updated according the content of the PSL Timebase
register.

Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>

---
This patch applies on top of this patch:
 http://patchwork.ozlabs.org/patch/873663/

Changelog[v3]
 - Rebased to latest upstream.
 - Dynamic update is now applied to P8.

Changelog[v2]
 - Missing Signed-off-by.
 - Spaces required around the ':'.
---
 drivers/misc/cxl/pci.c   | 17 -----------------
 drivers/misc/cxl/sysfs.c | 10 ++++++++++
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 66eed6a..3247eaf 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -606,9 +606,6 @@ static u64 timebase_read_xsl(struct cxl *adapter)
 
 static void cxl_setup_psl_timebase(struct cxl *adapter, struct pci_dev *dev)
 {
-	u64 psl_tb;
-	int delta;
-	unsigned int retry = 0;
 	struct device_node *np;
 
 	adapter->psl_timebase_synced = false;
@@ -636,20 +633,6 @@ static void cxl_setup_psl_timebase(struct cxl *adapter, struct pci_dev *dev)
 	cxl_p1_write(adapter, CXL_PSL_Control, 0x0000000000000000);
 	cxl_p1_write(adapter, CXL_PSL_Control, CXL_PSL_Control_tb);
 
-	/* Wait until CORE TB and PSL TB difference <= 16usecs */
-	do {
-		msleep(1);
-		if (retry++ > 5) {
-			dev_info(&dev->dev, "PSL timebase can't synchronize\n");
-			return;
-		}
-		psl_tb = adapter->native->sl_ops->timebase_read(adapter);
-		delta = mftb() - psl_tb;
-		if (delta < 0)
-			delta = -delta;
-	} while (tb_to_ns(delta) > 16000);
-
-	adapter->psl_timebase_synced = true;
 	return;
 }
 
diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index a8b6d6a..3f758d9 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/drivers/misc/cxl/sysfs.c
@@ -62,6 +62,16 @@ static ssize_t psl_timebase_synced_show(struct device *device,
 					char *buf)
 {
 	struct cxl *adapter = to_cxl_adapter(device);
+	u64 psl_tb;
+	int delta;
+
+	psl_tb = adapter->native->sl_ops->timebase_read(adapter);
+	delta = mftb() - psl_tb;
+	if (delta < 0)
+		delta = -delta;
+
+	/* CORE TB and PSL TB difference <= 16usecs ? */
+	adapter->psl_timebase_synced = (tb_to_ns(delta) < 16000) ? true : false;
 
 	return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->psl_timebase_synced);
 }
-- 
2.7.4

Re: [PATCH V3] cxl: Fix timebase synchronization status on P9

[Vaibhav Jain]

Hi Christophe,

Mostly ok with this patch. Some very minor review comments:

Christophe Lombard <clombard@linux.vnet.ibm.com> writes:
> --- a/drivers/misc/cxl/sysfs.c
> +++ b/drivers/misc/cxl/sysfs.c
> @@ -62,6 +62,16 @@ static ssize_t psl_timebase_synced_show(struct device *device,
>  					char *buf)
>  {
>  	struct cxl *adapter = to_cxl_adapter(device);
> +	u64 psl_tb;
> +	int delta;
> +
> +	psl_tb = adapter->native->sl_ops->timebase_read(adapter);
> +	delta = mftb() - psl_tb;
> +	if (delta < 0)
> +		delta = -delta;
Can just use abs().
> +
> +	/* CORE TB and PSL TB difference <= 16usecs ? */
> +	adapter->psl_timebase_synced = (tb_to_ns(delta) < 16000) ? true : false;
Can be re-written as
'adapter->psl_timebase_synced = (tb_to_ns(abs(delta)) < 16000);'

>
>  	return scnprintf(buf, PAGE_SIZE, "%i\n",
>  	adapter->psl_timebase_synced);
Might be a good idea to debug print/print_once the delta.

-- 
Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Linux Technology Center, IBM India Pvt. Ltd.

Re: [PATCH V3] cxl: Fix timebase synchronization status on P9

[christophe lombard]

Le 19/02/2018 à 07:10, Vaibhav Jain a écrit :
> 
> Hi Christophe,
> 
> Mostly ok with this patch. Some very minor review comments:
> 
> Christophe Lombard <clombard@linux.vnet.ibm.com> writes:
>> --- a/drivers/misc/cxl/sysfs.c
>> +++ b/drivers/misc/cxl/sysfs.c
>> @@ -62,6 +62,16 @@ static ssize_t psl_timebase_synced_show(struct device *device,
>>   					char *buf)
>>   {
>>   	struct cxl *adapter = to_cxl_adapter(device);
>> +	u64 psl_tb;
>> +	int delta;
>> +
>> +	psl_tb = adapter->native->sl_ops->timebase_read(adapter);
>> +	delta = mftb() - psl_tb;
>> +	if (delta < 0)
>> +		delta = -delta;
> Can just use abs().

okay, I can.

>> +
>> +	/* CORE TB and PSL TB difference <= 16usecs ? */
>> +	adapter->psl_timebase_synced = (tb_to_ns(delta) < 16000) ? true : false;
> Can be re-written as
> 'adapter->psl_timebase_synced = (tb_to_ns(abs(delta)) < 16000);'

I prefer to keep the original version for easier reading.

> 
>>
>>   	return scnprintf(buf, PAGE_SIZE, "%i\n",
>>   	adapter->psl_timebase_synced);
> Might be a good idea to debug print/print_once the delta.

sounds good.

>