[PATCH 4/4] i915: POC use dynamic_debug_exec_queries to control pr_debugs in gvt

[Jim Cromie]

The gvt component of this driver has ~120 pr_debugs, in 9 "classes".
Add a "knob", like drm.debug, to map bits to these classes.

bash-5.0# echo 0x01 > /sys/module/i915/parameters/debug_dyn
 set_dyndbg: result:0x1 from 0x01
 dyndbg: query 0: "format='^gvt: cmd: ' +p"
 dyndbg: entry, buf:'format='^gvt: cmd: ' +p'
 dyndbg: start-of-word:0 'format='^gvt: cmd: ' +p'
 dyndbg: start-of-word:1 ''^gvt: cmd: ' +p'
 dyndbg: start-of-word:2 '+p'
 dyndbg: split into words: "format" "^gvt: cmd: " "+p"
 dyndbg: op='+'
 dyndbg: flags=0x1
 dyndbg: *flagsp=0x1 *maskp=0xffffffff
 dyndbg: key:'format' arg:'^gvt: cmd: '
 dyndbg: parsed: func="" file="" module="i915" format="^gvt: cmd: " lineno=0-0
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:3081 [i915]init_cmd_table =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:1376 [i915]gen8_check_mi_display_flip =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:1373 [i915]gen8_check_mi_display_flip =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:745 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:744 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:742 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:733 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:729 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:722 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:716 [i915]parser_exec_state_dump =p
 dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:691 [i915]print_opcode =p
 dyndbg: applied: func="" file="" module="i915" format="^gvt: cmd: " lineno=0-0
 dyndbg: processed 1 queries, with 11 matches, 0 errs
 change ct:11 on format='gvt: cmd: '
 change ct:11

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_params.c | 76 ++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 8d8db9ff0a48..4e1f01ab4865 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -255,3 +255,79 @@ void i915_params_free(struct i915_params *params)
 	I915_PARAMS_FOR_EACH(FREE);
 #undef FREE
 }
+
+/* POC for callback -> dynamic_debug_exec_queries */
+unsigned long __new_knob;
+EXPORT_SYMBOL(__new_knob);
+
+static char *pr_debug_classes[] = {
+	"gvt: cmd: ",
+	"gvt: core: ",
+	"gvt: dpy: ",
+	"gvt: el: ",
+	"gvt: irq: ",
+	"gvt: mm: ",
+	"gvt: mmio: ",
+	"gvt: render: ",
+	"gvt: sched: "
+};
+#define NUM_CLASSES	ARRAY_SIZE(pr_debug_classes)
+#define OUR_QUERY_SIZE	128 /* we need about 20 */
+
+#include <linux/module.h>
+
+static int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{
+	static unsigned long int old_val;
+        unsigned int val;
+	unsigned long int changes, result;
+	int rc, chgct = 0, totct = 0, bitpos;
+	char query[OUR_QUERY_SIZE];
+
+	rc = kstrtouint(instr, 0, &val);
+	if (rc) {
+		pr_err("set_dyndbg: failed\n");
+		return -EINVAL;
+	}
+	result = val;
+	pr_info("set_dyndbg: result:0x%lx from %s\n", result, instr);
+
+	changes = result ^ old_val;
+
+	for_each_set_bit(bitpos, &changes, NUM_CLASSES) {
+
+		sprintf(query, "format='^%s' %cp", pr_debug_classes[bitpos],
+			test_bit(bitpos, &result) ? '+' : '-');
+
+		chgct = dynamic_debug_exec_queries(query, "i915");
+		totct += chgct;
+		pr_info("change ct:%d on format='%s'\n", chgct,
+			pr_debug_classes[bitpos]);
+	}
+	old_val = result;
+	pr_info("change ct:%d\n", totct);
+	return 0;
+}
+static int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{
+	return scnprintf(buffer, PAGE_SIZE, "%u\n",
+			 *((unsigned int *)kp->arg));
+}
+static const struct kernel_param_ops param_ops_dyndbg = {
+	.set = param_set_dyndbg,
+	.get = param_get_dyndbg,
+};
+
+MODULE_PARM_DESC(debug_dyn, " enable dynamic-debug by format-string classifications.\n"
+		 "\t\twhich are:"
+		 "\n\t\t gvt: cmd:"
+		 "\n\t\t gvt: core:"
+		 "\n\t\t gvt: dpy:"
+		 "\n\t\t gvt: el:"
+		 "\n\t\t gvt: irq:"
+		 "\n\t\t gvt: mm:"
+		 "\n\t\t gvt: mmio:"
+		 "\n\t\t gvt: render:"
+		 "\n\t\t gvt: sched:" "\n");
+
+module_param_cb(debug_dyn, &param_ops_dyndbg, &__new_knob, 0644);
-- 
2.26.2