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

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 <redacted>

---
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

Hi Christophe,

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

Christophe Lombard [off-list ref] writes:

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 [off-list ref]
Linux Technology Center, IBM India Pvt. Ltd.

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 [off-list ref] writes:

quoted

--- 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.

quoted

+
+	/* 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.

quoted

  	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.