[PATCH v4 2/3] powerpc/papr_scm: Update drc_pmem_unbind() to use H_SCM_UNBIND_ALL

[Vaibhav Jain <vaibhav@linux.ibm.com>]

The new hcall named H_SCM_UNBIND_ALL has been introduce that can
unbind all or specific scm memory assigned to an lpar. This is
more efficient than using H_SCM_UNBIND_MEM as currently we don't
support partial unbind of scm memory.

Hence this patch proposes following changes to drc_pmem_unbind():

    * Update drc_pmem_unbind() to replace hcall H_SCM_UNBIND_MEM to
      H_SCM_UNBIND_ALL.

    * Update drc_pmem_unbind() to handles cases when PHYP asks the guest
      kernel to wait for specific amount of time before retrying the
      hcall via the 'LONG_BUSY' return value.

    * Ensure appropriate error code is returned back from the function
      in case of an error.

Reviewed-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
Change-log:

v4:
* None. Re-spinning the patchset.

v3:
* Fixed a build warning reported by kbuild-robot.
* Updated patch description to put emphasis on 'scm memory' instead of
  'scm drc memory blocks' as for phyp there is a stark difference
  between how drc are managed for scm memory v/s regular memory. [Oliver]

v2:
* Added a dev_dbg when unbind operation succeeds [Oliver]
* Changed type of variable 'rc' to int64_t [Oliver]
* Removed the code that was logging a warning in case bind operation
  takes >1-seconds [Oliver]
* Spinned off changes to hvcall.h as a separate patch. [Oliver]
---
 arch/powerpc/platforms/pseries/papr_scm.c | 29 +++++++++++++++++------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 96c53b23e58f..c01a03fd3ee7 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/libnvdimm.h>
 #include <linux/platform_device.h>
+#include <linux/delay.h>
 
 #include <asm/plpar_wrappers.h>
 
@@ -77,22 +78,36 @@ static int drc_pmem_bind(struct papr_scm_priv *p)
 static int drc_pmem_unbind(struct papr_scm_priv *p)
 {
 	unsigned long ret[PLPAR_HCALL_BUFSIZE];
-	uint64_t rc, token;
+	uint64_t token = 0;
+	int64_t rc;
 
-	token = 0;
+	dev_dbg(&p->pdev->dev, "unbind drc %x\n", p->drc_index);
 
-	/* NB: unbind has the same retry requirements mentioned above */
+	/* NB: unbind has the same retry requirements as drc_pmem_bind() */
 	do {
-		rc = plpar_hcall(H_SCM_UNBIND_MEM, ret, p->drc_index,
-				p->bound_addr, p->blocks, token);
+
+		/* Unbind of all SCM resources associated with drcIndex */
+		rc = plpar_hcall(H_SCM_UNBIND_ALL, ret, H_UNBIND_SCOPE_DRC,
+				 p->drc_index, token);
 		token = ret[0];
-		cond_resched();
+
+		/* Check if we are stalled for some time */
+		if (H_IS_LONG_BUSY(rc)) {
+			msleep(get_longbusy_msecs(rc));
+			rc = H_BUSY;
+		} else if (rc == H_BUSY) {
+			cond_resched();
+		}
+
 	} while (rc == H_BUSY);
 
 	if (rc)
 		dev_err(&p->pdev->dev, "unbind error: %lld\n", rc);
+	else
+		dev_dbg(&p->pdev->dev, "unbind drc %x complete\n",
+			p->drc_index);
 
-	return !!rc;
+	return rc == H_SUCCESS ? 0 : -ENXIO;
 }
 
 static int papr_scm_meta_get(struct papr_scm_priv *p,
-- 
2.21.0