drm/xe/oa: Enable Xe2+ overrun mode

Enable Xe2+ overrun mode. For Xe2+, when overrun mode is enabled, there are
no partial reports at the end of buffer, making the OA buffer effectively a
non-power-of-2 size circular buffer whose size, circ_size, is a multiple of
the report size.

v2: Fix implementation of xe_oa_circ_diff/xe_oa_circ_incr (Umesh)
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618014609.3233427-18-ashutosh.dixit@intel.com

drivers/gpu/drm/xe/xe_oa.c

@@ -114,7 +114,14 @@ static const struct xe_oa_format oa_formats[] = {
 
 static u32 xe_oa_circ_diff(struct xe_oa_stream *stream, u32 tail, u32 head)
 {
-	return (tail - head) & (XE_OA_BUFFER_SIZE - 1);
+	return tail >= head ? tail - head :
+		tail + stream->oa_buffer.circ_size - head;
+}
+
+static u32 xe_oa_circ_incr(struct xe_oa_stream *stream, u32 ptr, u32 n)
+{
+	return ptr + n >= stream->oa_buffer.circ_size ?
+		ptr + n - stream->oa_buffer.circ_size : ptr + n;
 }
 
 static void xe_oa_config_release(struct kref *ref)
@@ -288,7 +295,7 @@ static int xe_oa_append_report(struct xe_oa_stream *stream, char __user *buf,
 
 	buf += *offset;
 
-	oa_buf_end = stream->oa_buffer.vaddr + XE_OA_BUFFER_SIZE;
+	oa_buf_end = stream->oa_buffer.vaddr + stream->oa_buffer.circ_size;
 	report_size_partial = oa_buf_end - report;
 
 	if (report_size_partial < report_size) {
@@ -314,7 +321,6 @@ static int xe_oa_append_reports(struct xe_oa_stream *stream, char __user *buf,
 	int report_size = stream->oa_buffer.format->size;
 	u8 *oa_buf_base = stream->oa_buffer.vaddr;
 	u32 gtt_offset = xe_bo_ggtt_addr(stream->oa_buffer.bo);
-	u32 mask = (XE_OA_BUFFER_SIZE - 1);
 	size_t start_offset = *offset;
 	unsigned long flags;
 	u32 head, tail;
@@ -325,21 +331,23 @@ static int xe_oa_append_reports(struct xe_oa_stream *stream, char __user *buf,
 	tail = stream->oa_buffer.tail;
 	spin_unlock_irqrestore(&stream->oa_buffer.ptr_lock, flags);
 
-	xe_assert(stream->oa->xe, head < XE_OA_BUFFER_SIZE && tail < XE_OA_BUFFER_SIZE);
+	xe_assert(stream->oa->xe,
+		  head < stream->oa_buffer.circ_size && tail < stream->oa_buffer.circ_size);
 
-	for (; xe_oa_circ_diff(stream, tail, head); head = (head + report_size) & mask) {
+	for (; xe_oa_circ_diff(stream, tail, head);
+	     head = xe_oa_circ_incr(stream, head, report_size)) {
 		u8 *report = oa_buf_base + head;
 
 		ret = xe_oa_append_report(stream, buf, count, offset, report);
 		if (ret)
 			break;
 
-		if (is_power_of_2(report_size)) {
+		if (!(stream->oa_buffer.circ_size % report_size)) {
 			/* Clear out report id and timestamp to detect unlanded reports */
 			oa_report_id_clear(stream, (void *)report);
 			oa_timestamp_clear(stream, (void *)report);
 		} else {
-			u8 *oa_buf_end = stream->oa_buffer.vaddr + XE_OA_BUFFER_SIZE;
+			u8 *oa_buf_end = stream->oa_buffer.vaddr + stream->oa_buffer.circ_size;
 			u32 part = oa_buf_end - report;
 
 			/* Zero out the entire report */
@@ -377,7 +385,6 @@ static void xe_oa_init_oa_buffer(struct xe_oa_stream *stream)
 	xe_mmio_write32(stream->gt, __oa_regs(stream)->oa_head_ptr,
 			gtt_offset & OAG_OAHEADPTR_MASK);
 	stream->oa_buffer.head = 0;
-
 	/*
 	 * PRM says: "This MMIO must be set before the OATAILPTR register and after the
 	 * OAHEADPTR register. This is to enable proper functionality of the overflow bit".
@@ -1300,6 +1307,18 @@ static int xe_oa_stream_init(struct xe_oa_stream *stream,
 	stream->periodic = param->period_exponent > 0;
 	stream->period_exponent = param->period_exponent;
 
+	/*
+	 * For Xe2+, when overrun mode is enabled, there are no partial reports at the end
+	 * of buffer, making the OA buffer effectively a non-power-of-2 size circular
+	 * buffer whose size, circ_size, is a multiple of the report size
+	 */
+	if (GRAPHICS_VER(stream->oa->xe) >= 20 &&
+	    stream->hwe->oa_unit->type == DRM_XE_OA_UNIT_TYPE_OAG && stream->sample)
+		stream->oa_buffer.circ_size =
+			XE_OA_BUFFER_SIZE - XE_OA_BUFFER_SIZE % stream->oa_buffer.format->size;
+	else
+		stream->oa_buffer.circ_size = XE_OA_BUFFER_SIZE;
+
 	if (stream->exec_q && engine_supports_mi_query(stream->hwe)) {
 		/* If we don't find the context offset, just return error */
 		ret = xe_oa_set_ctx_ctrl_offset(stream);

drivers/gpu/drm/xe/xe_oa_types.h

@@ -170,6 +170,9 @@ struct xe_oa_buffer {
 
 	/** @tail: The last verified cached tail where HW has completed writing */
 	u32 tail;
+
+	/** @circ_size: The effective circular buffer size, for Xe2+ */
+	u32 circ_size;
 };
 
 /**