[PATCH V4] cxl: Add support for ASB_Notify on POWER9

[Christophe Lombard]

The POWER9 core supports a new feature: ASB_Notify which requires the
support of the Special Purpose Register: TIDR.

The ASB_Notify command, generated by the AFU, will attempt to
wake-up the host thread identified by the particular LPID:PID:TID.

This patch assign a unique TIDR (thread id) for the current thread which
will be used in the process element entry.

A next patch will handle a new kind of "compatible" property in the
device-tree (PHB DT node) indicating which version of CAPI and which
features are supported, instead of handling PVR values.

Signed-off-by: Christophe Lombard <clombard at linux.vnet.ibm.com>
Reviewed-by: Philippe Bergheaud <felix at linux.vnet.ibm.com>

---
Changelog[v4]
 - Rebased to latest upstream.
 - Updated the ioctl interface.
 - Removed the field tid in the context structure.

Changelog[v3]
 - Rebased to latest upstream.
 - Updated attr->tid field in cxllib_get_PE_attributes().

Changelog[v2]
 - Rebased to latest upstream.
 - Updated the ioctl interface.
 - Added a checking to allow updating the TIDR if a P9 chip is present.
---
 arch/powerpc/kernel/process.c |  1 +
 drivers/misc/cxl/context.c    | 15 +++++++++++++++
 drivers/misc/cxl/cxl.h        |  3 +++
 drivers/misc/cxl/cxllib.c     |  3 ++-
 drivers/misc/cxl/file.c       |  7 +++++++
 drivers/misc/cxl/native.c     |  2 +-
 include/uapi/misc/cxl.h       |  4 +++-
 7 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5acb5a1..a6a70e2 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1589,6 +1589,7 @@ int set_thread_tidr(struct task_struct *t)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(set_thread_tidr);
 
 #endif /* CONFIG_PPC64 */
 
diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 12a41b2..e309d35 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -22,6 +22,7 @@
 #include <asm/cputable.h>
 #include <asm/current.h>
 #include <asm/copro.h>
+#include <asm/switch_to.h>
 
 #include "cxl.h"
 
@@ -362,3 +363,17 @@ void cxl_context_mm_count_put(struct cxl_context *ctx)
 	if (ctx->mm)
 		mmdrop(ctx->mm);
 }
+
+int cxl_context_thread_tidr(struct cxl_context *ctx)
+{
+	int rc = 0;
+
+	if (!cxl_is_power9())
+		return -ENODEV;
+
+	rc = set_thread_tidr(current);
+	pr_devel("%s: current tidr: %ld\n", __func__,
+		 current->thread.tidr);
+
+	return rc;
+}
diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index e46a406..1a5db0b 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -1169,4 +1169,7 @@ void cxl_context_mm_count_get(struct cxl_context *ctx);
 /* Decrements the reference count to "struct mm_struct" */
 void cxl_context_mm_count_put(struct cxl_context *ctx);
 
+/* Handles an unique TIDR (thread id) for the current thread */
+int cxl_context_thread_tidr(struct cxl_context *ctx);
+
 #endif
diff --git a/drivers/misc/cxl/cxllib.c b/drivers/misc/cxl/cxllib.c
index dc9bc18..30ccba4 100644
--- a/drivers/misc/cxl/cxllib.c
+++ b/drivers/misc/cxl/cxllib.c
@@ -199,10 +199,11 @@ int cxllib_get_PE_attributes(struct task_struct *task,
 		 */
 		attr->pid = mm->context.id;
 		mmput(mm);
+		attr->tid = task->thread.tidr;
 	} else {
 		attr->pid = 0;
+		attr->tid = 0;
 	}
-	attr->tid = 0;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cxllib_get_PE_attributes);
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 76c0b0c..a823c76 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -248,6 +248,13 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 	 */
 	smp_mb();
 
+	/* Assign a unique TIDR (thread id) for the current thread */
+	if (work.flags & CXL_START_WORK_TID) {
+		rc = cxl_context_thread_tidr(ctx);
+		if (rc)
+			goto out;
+	}
+
 	trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
 
 	if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor,
diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index 02b6b45..036fe5b 100644
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -673,7 +673,7 @@ static int process_element_entry_psl9(struct cxl_context *ctx, u64 wed, u64 amr)
 		pid = ctx->mm->context.id;
 	}
 
-	ctx->elem->common.tid = 0;
+	ctx->elem->common.tid = cpu_to_be32(current->thread.tidr);
 	ctx->elem->common.pid = cpu_to_be32(pid);
 
 	ctx->elem->sr = cpu_to_be64(calculate_sr(ctx));
diff --git a/include/uapi/misc/cxl.h b/include/uapi/misc/cxl.h
index 49e8fd0..980ee8f 100644
--- a/include/uapi/misc/cxl.h
+++ b/include/uapi/misc/cxl.h
@@ -31,9 +31,11 @@ struct cxl_ioctl_start_work {
 #define CXL_START_WORK_AMR		0x0000000000000001ULL
 #define CXL_START_WORK_NUM_IRQS		0x0000000000000002ULL
 #define CXL_START_WORK_ERR_FF		0x0000000000000004ULL
+#define CXL_START_WORK_TID		0x0000000000000008ULL
 #define CXL_START_WORK_ALL		(CXL_START_WORK_AMR |\
 					 CXL_START_WORK_NUM_IRQS |\
-					 CXL_START_WORK_ERR_FF)
+					 CXL_START_WORK_ERR_FF |\
+					 CXL_START_WORK_TID)
 
 
 /* Possible modes that an afu can be in */
-- 
2.7.4