[PATCH v5 60/69] drm/vc4: vec: Protect device resources after removal

[Maxime Ripard]

Whenever the device and driver are unbound, the main device and all the
subdevices will be removed by calling their unbind() method.

However, the DRM device itself will only be freed when the last user will
have closed it.

It means that there is a time window where the device and its resources
aren't there anymore, but the userspace can still call into our driver.

Fortunately, the DRM framework provides the drm_dev_enter() and
drm_dev_exit() functions to make sure our underlying device is still there
for the section protected by those calls. Let's add them to the VEC driver.

Acked-by: Thomas Zimmermann <tzimmermann at suse.de>
Signed-off-by: Maxime Ripard <maxime at cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_vec.c | 67 +++++++++++++++++++++++++++++++----
 1 file changed, 61 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_vec.c b/drivers/gpu/drm/vc4/vc4_vec.c
index 4b843b18c006..df6adef96050 100644
--- a/drivers/gpu/drm/vc4/vc4_vec.c
+++ b/drivers/gpu/drm/vc4/vc4_vec.c
@@ -14,6 +14,7 @@
  */
 
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_panel.h>
 #include <drm/drm_probe_helper.h>
@@ -225,14 +226,30 @@ static const struct debugfs_reg32 vec_regs[] = {
 
 static void vc4_vec_ntsc_mode_set(struct vc4_vec *vec)
 {
+	struct drm_device *drm = vec->connector.dev;
+	int idx;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
+
 	VEC_WRITE(VEC_CONFIG0, VEC_CONFIG0_NTSC_STD | VEC_CONFIG0_PDEN);
 	VEC_WRITE(VEC_CONFIG1, VEC_CONFIG1_C_CVBS_CVBS);
+
+	drm_dev_exit(idx);
 }
 
 static void vc4_vec_ntsc_j_mode_set(struct vc4_vec *vec)
 {
+	struct drm_device *drm = vec->connector.dev;
+	int idx;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
+
 	VEC_WRITE(VEC_CONFIG0, VEC_CONFIG0_NTSC_STD);
 	VEC_WRITE(VEC_CONFIG1, VEC_CONFIG1_C_CVBS_CVBS);
+
+	drm_dev_exit(idx);
 }
 
 static const struct drm_display_mode ntsc_mode = {
@@ -244,17 +261,33 @@ static const struct drm_display_mode ntsc_mode = {
 
 static void vc4_vec_pal_mode_set(struct vc4_vec *vec)
 {
+	struct drm_device *drm = vec->connector.dev;
+	int idx;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
+
 	VEC_WRITE(VEC_CONFIG0, VEC_CONFIG0_PAL_BDGHI_STD);
 	VEC_WRITE(VEC_CONFIG1, VEC_CONFIG1_C_CVBS_CVBS);
+
+	drm_dev_exit(idx);
 }
 
 static void vc4_vec_pal_m_mode_set(struct vc4_vec *vec)
 {
+	struct drm_device *drm = vec->connector.dev;
+	int idx;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
+
 	VEC_WRITE(VEC_CONFIG0, VEC_CONFIG0_PAL_BDGHI_STD);
 	VEC_WRITE(VEC_CONFIG1,
 		  VEC_CONFIG1_C_CVBS_CVBS | VEC_CONFIG1_CUSTOM_FREQ);
 	VEC_WRITE(VEC_FREQ3_2, 0x223b);
 	VEC_WRITE(VEC_FREQ1_0, 0x61d1);
+
+	drm_dev_exit(idx);
 }
 
 static const struct drm_display_mode pal_mode = {
@@ -344,8 +377,12 @@ static int vc4_vec_connector_init(struct drm_device *dev, struct vc4_vec *vec)
 
 static void vc4_vec_encoder_disable(struct drm_encoder *encoder)
 {
+	struct drm_device *drm = encoder->dev;
 	struct vc4_vec *vec = encoder_to_vc4_vec(encoder);
-	int ret;
+	int idx, ret;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
 
 	VEC_WRITE(VEC_CFG, 0);
 	VEC_WRITE(VEC_DAC_MISC,
@@ -359,19 +396,29 @@ static void vc4_vec_encoder_disable(struct drm_encoder *encoder)
 	ret = pm_runtime_put(&vec->pdev->dev);
 	if (ret < 0) {
 		DRM_ERROR("Failed to release power domain: %d\n", ret);
-		return;
+		goto err_dev_exit;
 	}
+
+	drm_dev_exit(idx);
+	return;
+
+err_dev_exit:
+	drm_dev_exit(idx);
 }
 
 static void vc4_vec_encoder_enable(struct drm_encoder *encoder)
 {
+	struct drm_device *drm = encoder->dev;
 	struct vc4_vec *vec = encoder_to_vc4_vec(encoder);
-	int ret;
+	int idx, ret;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
 
 	ret = pm_runtime_get_sync(&vec->pdev->dev);
 	if (ret < 0) {
 		DRM_ERROR("Failed to retain power domain: %d\n", ret);
-		return;
+		goto err_dev_exit;
 	}
 
 	/*
@@ -384,13 +431,13 @@ static void vc4_vec_encoder_enable(struct drm_encoder *encoder)
 	ret = clk_set_rate(vec->clock, 108000000);
 	if (ret) {
 		DRM_ERROR("Failed to set clock rate: %d\n", ret);
-		return;
+		goto err_put_runtime_pm;
 	}
 
 	ret = clk_prepare_enable(vec->clock);
 	if (ret) {
 		DRM_ERROR("Failed to turn on core clock: %d\n", ret);
-		return;
+		goto err_put_runtime_pm;
 	}
 
 	/* Reset the different blocks */
@@ -426,6 +473,14 @@ static void vc4_vec_encoder_enable(struct drm_encoder *encoder)
 	VEC_WRITE(VEC_DAC_MISC,
 		  VEC_DAC_MISC_VID_ACT | VEC_DAC_MISC_DAC_RST_N);
 	VEC_WRITE(VEC_CFG, VEC_CFG_VEC_EN);
+
+	drm_dev_exit(idx);
+	return;
+
+err_put_runtime_pm:
+	pm_runtime_put(&vec->pdev->dev);
+err_dev_exit:
+	drm_dev_exit(idx);
 }
 
 
-- 
2.36.1