linux-kernel - [PATCH v2 3/8] drm/lima: set pp bus

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Date: Wed, 24 Jan 2024 03:59:42 +0100
From: Erico Nunes <nunes.erico@...il.com>
To: Qiang Yu <yuq825@...il.com>,
	anarsoul@...il.com,
	christian.koenig@....com,
	dri-devel@...ts.freedesktop.org,
	lima@...ts.freedesktop.org
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	linux-kernel@...r.kernel.org,
	Erico Nunes <nunes.erico@...il.com>
Subject: [PATCH v2 3/8] drm/lima: set pp bus_stop bit before hard reset

This is required for reliable hard resets. Otherwise, doing a hard reset
while a task is still running (such as a task which is being stopped by
the drm_sched timeout handler) may result in random mmu write timeouts
or lockups which cause the entire gpu to hang.

Signed-off-by: Erico Nunes <nunes.erico@...il.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@...il.com>
---
 drivers/gpu/drm/lima/lima_pp.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/lima/lima_pp.c b/drivers/gpu/drm/lima/lima_pp.c
index a8f8f63b8295..ac097dd75072 100644
--- a/drivers/gpu/drm/lima/lima_pp.c
+++ b/drivers/gpu/drm/lima/lima_pp.c
@@ -168,6 +168,11 @@ static void lima_pp_write_frame(struct lima_ip *ip, u32 *frame, u32 *wb)
 	}
 }
 
+static int lima_pp_bus_stop_poll(struct lima_ip *ip)
+{
+	return !!(pp_read(LIMA_PP_STATUS) & LIMA_PP_STATUS_BUS_STOPPED);
+}
+
 static int lima_pp_hard_reset_poll(struct lima_ip *ip)
 {
 	pp_write(LIMA_PP_PERF_CNT_0_LIMIT, 0xC01A0000);
@@ -181,6 +186,14 @@ static int lima_pp_hard_reset(struct lima_ip *ip)
 
 	pp_write(LIMA_PP_PERF_CNT_0_LIMIT, 0xC0FFE000);
 	pp_write(LIMA_PP_INT_MASK, 0);
+
+	pp_write(LIMA_PP_CTRL, LIMA_PP_CTRL_STOP_BUS);
+	ret = lima_poll_timeout(ip, lima_pp_bus_stop_poll, 10, 100);
+	if (ret) {
+		dev_err(dev->dev, "pp %s bus stop timeout\n", lima_ip_name(ip));
+		return ret;
+	}
+
 	pp_write(LIMA_PP_CTRL, LIMA_PP_CTRL_FORCE_RESET);
 	ret = lima_poll_timeout(ip, lima_pp_hard_reset_poll, 10, 100);
 	if (ret) {
-- 
2.43.0