[Intel-gfx] [PATCH igt] tests/gem_workarounds: Skip write only registers

[Mika Kuoppala]

We have no means to check write only registers as
this would need access through context image. For now we
know that cnl has a one such register, 0xe5f0 which is used
to set WaForceContextSaveRestoreNonCoherent:cnl. By inspecting
the context image without and with workaround applied:

0x0000a840: 0x0000e5f0 0xffff0800
0x0000a840: 0x0000e5f0 0xffff0820

we can conclude that the workaround setup is working right
in this particular case.

Add a write only list and add register 0xe5f0 into this list.
This is a temporary solution until a more capable context image
checker emerges.

v2: add code comment about adhocness (Petri)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102943
Cc: Oscar Mateo <oscar.mateo at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Petri Latvala <petri.latvala at intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 tests/gem_workarounds.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/tests/gem_workarounds.c b/tests/gem_workarounds.c
index d6641bd5..5e30a7b8 100644
--- a/tests/gem_workarounds.c
+++ b/tests/gem_workarounds.c
@@ -29,6 +29,8 @@
 
 #include <fcntl.h>
 
+static int gen;
+
 enum operation {
 	GPU_RESET,
 	SUSPEND_RESUME,
@@ -41,6 +43,21 @@ struct intel_wa_reg {
 	uint32_t mask;
 };
 
+static struct write_only_list {
+	unsigned int gen;
+	uint32_t addr;
+} wo_list[] = {
+	{ 10, 0xE5F0 } /* WaForceContextSaveRestoreNonCoherent:cnl */
+
+	/*
+	 * FIXME: If you are contemplating adding stuff here
+	 * consider this as a temporary solution. You need to
+	 * manually check from context image that your workaround
+	 * is having an effect. Consider creating a context image
+	 * validator to act as a superior solution.
+	 */
+};
+
 static struct intel_wa_reg *wa_regs;
 static int num_wa_regs;
 
@@ -64,6 +81,21 @@ static void test_suspend_resume(void)
 	igt_system_suspend_autoresume(SUSPEND_STATE_MEM, SUSPEND_TEST_NONE);
 }
 
+static bool write_only(const uint32_t addr)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(wo_list); i++) {
+		if (gen == wo_list[i].gen &&
+		    addr == wo_list[i].addr) {
+			igt_info("Skipping check for 0x%x due to write only\n", addr);
+			return true;
+		}
+	}
+
+	return false;
+}
+
 static int workaround_fail_count(void)
 {
 	int i, fail_count = 0;
@@ -85,6 +117,9 @@ static int workaround_fail_count(void)
 			  wa_regs[i].addr, wa_regs[i].value, wa_regs[i].mask,
 			  val, ok ? "OK" : "FAIL");
 
+		if (write_only(wa_regs[i].addr))
+			continue;
+
 		if (!ok) {
 			igt_warn("0x%05X\t0x%08X\t0x%08X\t0x%08X\t%s\n",
 				 wa_regs[i].addr, wa_regs[i].value,
@@ -124,7 +159,6 @@ igt_main
 {
 	igt_fixture {
 		int device = drm_open_driver_master(DRIVER_INTEL);
-		const int gen = intel_gen(intel_get_drm_devid(device));
 		struct pci_device *pci_dev;
 		FILE *file;
 		char *line = NULL;
@@ -133,6 +167,8 @@ igt_main
 
 		igt_require_gem(device);
 
+		gen = intel_gen(intel_get_drm_devid(device));
+
 		pci_dev = intel_get_pci_device();
 		igt_require(pci_dev);
 
-- 
2.11.0