linux-kernel - [PATCH v2] drm/panthor: Simplify FW fast reset path

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Message-Id: <20241119135030.3352939-1-karunika.choo@arm.com>
Date: Tue, 19 Nov 2024 13:50:29 +0000
From: Karunika Choo <karunika.choo@....com>
To: boris.brezillon@...labora.com
Cc: nd@....com,
	Steven Price <steven.price@....com>,
	Liviu Dudau <liviu.dudau@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/panthor: Simplify FW fast reset path

Stop checking the FW halt_status as MCU_STATUS should be sufficient.
This should make the check for successful FW halt and subsequently
setting fast_reset to true more robust.

We should also clear GLB_REQ.GLB_HALT bit only on post-reset prior
to starting the FW and only if we're doing a fast reset, because
the slow reset will re-initialize all FW sections, including the
global interface.

Signed-off-by: Karunika Choo <karunika.choo@....com>
---
v2:
- clarify comments and commit message with regards to when to clear the
  GLB_HALT flag.

 drivers/gpu/drm/panthor/panthor_fw.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
index ecca5565ce41..4bc52b1b1a28 100644
--- a/drivers/gpu/drm/panthor/panthor_fw.c
+++ b/drivers/gpu/drm/panthor/panthor_fw.c
@@ -1098,17 +1098,11 @@ void panthor_fw_pre_reset(struct panthor_device *ptdev, bool on_hang)
 		panthor_fw_update_reqs(glb_iface, req, GLB_HALT, GLB_HALT);
 		gpu_write(ptdev, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
 		if (!readl_poll_timeout(ptdev->iomem + MCU_STATUS, status,
-					status == MCU_STATUS_HALT, 10, 100000) &&
-		    glb_iface->output->halt_status == PANTHOR_FW_HALT_OK) {
+					status == MCU_STATUS_HALT, 10, 100000)) {
 			ptdev->fw->fast_reset = true;
 		} else {
 			drm_warn(&ptdev->base, "Failed to cleanly suspend MCU");
 		}
-
-		/* The FW detects 0 -> 1 transitions. Make sure we reset
-		 * the HALT bit before the FW is rebooted.
-		 */
-		panthor_fw_update_reqs(glb_iface, req, 0, GLB_HALT);
 	}
 
 	panthor_job_irq_suspend(&ptdev->fw->irq);
@@ -1134,6 +1128,13 @@ int panthor_fw_post_reset(struct panthor_device *ptdev)
 	 * the FW sections. If it fails, go for a full reset.
 	 */
 	if (ptdev->fw->fast_reset) {
+		/* The FW detects 0 -> 1 transitions. Make sure we reset
+		 * the HALT bit before the FW is rebooted.
+		 * This is not needed on a slow reset because FW sections are
+		 * re-initialized.
+		 */
+		panthor_fw_update_reqs(glb_iface, req, 0, GLB_HALT);
+
 		ret = panthor_fw_start(ptdev);
 		if (!ret)
 			goto out;
-- 
2.25.1