From 931e3f3a0e997c41eafbc88e4fc07ba9fef28f29 Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Mon, 2 May 2022 16:25:14 +0200
Subject: [PATCH] drm/mgag200: Protect concurrent access to I/O registers with
lock
Add a mutex lock to protect concurrent access to I/O registers
against each other. This happens between invocation of commit-
tail functions and get-mode operations. Both with use the CRTC
index registers MGA1064_GEN_IO_DATA and MGA1064_GEN_IO_CTL.
Concurrent access can lead to failed mode-setting operations.
v2:
* fix typo in commit description (Jocelyn)
* add comment to explain rmmio_lock
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220502142514.2174-4-tzimmermann@suse.de
---
drivers/gpu/drm/mgag200/mgag200_drv.c | 6 ++++++
drivers/gpu/drm/mgag200/mgag200_drv.h | 1 +
drivers/gpu/drm/mgag200/mgag200_mode.c | 14 ++++++++++++++
3 files changed, 21 insertions(+)
diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
index 217844d71ab5c..08839460606fe 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.c
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
@@ -14,6 +14,7 @@
#include <drm/drm_drv.h>
#include <drm/drm_file.h>
#include <drm/drm_ioctl.h>
+#include <drm/drm_managed.h>
#include <drm/drm_module.h>
#include <drm/drm_pciids.h>
@@ -65,6 +66,11 @@ static int mgag200_regs_init(struct mga_device *mdev)
struct pci_dev *pdev = to_pci_dev(dev->dev);
u32 option, option2;
u8 crtcext3;
+ int ret;
+
+ ret = drmm_mutex_init(dev, &mdev->rmmio_lock);
+ if (ret)
+ return ret;
switch (mdev->type) {
case G200_PCI:
diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
index 4368112023f7c..a18384c41fc4f 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.h
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
@@ -213,6 +213,7 @@ struct mga_device {
struct drm_device base;
unsigned long flags;
+ struct mutex rmmio_lock; /* Protects access to rmmio */
resource_size_t rmmio_base;
resource_size_t rmmio_size;
void __iomem *rmmio;
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index 6e18d3bbd7207..abde7655477db 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -881,6 +881,14 @@ mgag200_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
.y2 = fb->height,
};
+ /*
+ * Concurrent operations could possibly trigger a call to
+ * drm_connector_helper_funcs.get_modes by trying to read the
+ * display modes. Protect access to I/O registers by acquiring
+ * the I/O-register lock.
+ */
+ mutex_lock(&mdev->rmmio_lock);
+
if (mdev->type == G200_WB || mdev->type == G200_EW3)
mgag200_g200wb_hold_bmc(mdev);
@@ -904,6 +912,8 @@ mgag200_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
mgag200_enable_display(mdev);
mgag200_handle_damage(mdev, fb, &fullscreen, &shadow_plane_state->data[0]);
+
+ mutex_unlock(&mdev->rmmio_lock);
}
static void
@@ -963,8 +973,12 @@ mgag200_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
if (!fb)
return;
+ mutex_lock(&mdev->rmmio_lock);
+
if (drm_atomic_helper_damage_merged(old_state, state, &damage))
mgag200_handle_damage(mdev, fb, &damage, &shadow_plane_state->data[0]);
+
+ mutex_unlock(&mdev->rmmio_lock);
}
static struct drm_crtc_state *
--
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