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Message-ID: <d6e1e1ed82ec7ed904ed132e7ce1c61e945e0dee.camel@icenowy.me>
Date: Thu, 21 Aug 2025 11:48:10 +0800
From: Icenowy Zheng <uwu@...nowy.me>
To: Michal Wilczynski <m.wilczynski@...sung.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>, Rob Herring <robh@...nel.org>, Krzysztof
Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Drew
Fustini <fustini@...nel.org>, Guo Ren <guoren@...nel.org>, Fu Wei
<wefu@...hat.com>, Philipp Zabel <p.zabel@...gutronix.de>, Heiko Stuebner
<heiko@...ech.de>, Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong
<neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, Laurent
Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman
<jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>
Cc: Han Gao <rabenda.cn@...il.com>, Yao Zi <ziyao@...root.org>,
dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 3/8] drm: verisilicon: add a driver for Verisilicon
display controllers
在 2025-08-20星期三的 23:21 +0200，Michal Wilczynski写道：
>
>
> On 8/14/25 18:40, Icenowy Zheng wrote:
> > This is a from-scratch driver targeting Verisilicon DC-series
> > display
> > controllers, which feature self-identification functionality like
> > their
> > GC-series GPUs.
> >
> > Only DC8200 is being supported now, and only the main framebuffer
> > is set
> > up (as the DRM primary plane). Support for more DC models and more
> > features is my further targets.
> >
> > As the display controller is delivered to SoC vendors as a whole
> > part,
> > this driver does not use component framework and extra bridges
> > inside a
> > SoC is expected to be implemented as dedicated bridges (this driver
> > properly supports bridge chaining).
> >
> > Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> > ---
> > drivers/gpu/drm/Kconfig | 2 +
> > drivers/gpu/drm/Makefile | 1 +
> > drivers/gpu/drm/verisilicon/Kconfig | 15 +
> > drivers/gpu/drm/verisilicon/Makefile | 5 +
> > drivers/gpu/drm/verisilicon/vs_bridge.c | 330
> > ++++++++++++++++++
> > drivers/gpu/drm/verisilicon/vs_bridge.h | 40 +++
> > drivers/gpu/drm/verisilicon/vs_bridge_regs.h | 47 +++
> > drivers/gpu/drm/verisilicon/vs_crtc.c | 217 ++++++++++++
> > drivers/gpu/drm/verisilicon/vs_crtc.h | 29 ++
> > drivers/gpu/drm/verisilicon/vs_crtc_regs.h | 60 ++++
> > drivers/gpu/drm/verisilicon/vs_dc.c | 233 +++++++++++++
> > drivers/gpu/drm/verisilicon/vs_dc.h | 39 +++
> > drivers/gpu/drm/verisilicon/vs_dc_top_regs.h | 27 ++
> > drivers/gpu/drm/verisilicon/vs_drm.c | 177 ++++++++++
> > drivers/gpu/drm/verisilicon/vs_drm.h | 29 ++
> > drivers/gpu/drm/verisilicon/vs_hwdb.c | 150 ++++++++
> > drivers/gpu/drm/verisilicon/vs_hwdb.h | 29 ++
> > drivers/gpu/drm/verisilicon/vs_plane.c | 102 ++++++
> > drivers/gpu/drm/verisilicon/vs_plane.h | 68 ++++
> > .../gpu/drm/verisilicon/vs_primary_plane.c | 166 +++++++++
> > .../drm/verisilicon/vs_primary_plane_regs.h | 53 +++
> > 21 files changed, 1819 insertions(+)
> > create mode 100644 drivers/gpu/drm/verisilicon/Kconfig
> > create mode 100644 drivers/gpu/drm/verisilicon/Makefile
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_bridge.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_bridge.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_bridge_regs.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_crtc.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_crtc.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_crtc_regs.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_dc.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_dc.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_dc_top_regs.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_drm.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_drm.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_hwdb.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_hwdb.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_plane.c
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_plane.h
> > create mode 100644 drivers/gpu/drm/verisilicon/vs_primary_plane.c
> > create mode 100644
> > drivers/gpu/drm/verisilicon/vs_primary_plane_regs.h
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index f7ea8e895c0c0..33601485ecdba 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -396,6 +396,8 @@ source "drivers/gpu/drm/sprd/Kconfig"
> >
> > source "drivers/gpu/drm/imagination/Kconfig"
> >
> > +source "drivers/gpu/drm/verisilicon/Kconfig"
> > +
> > config DRM_HYPERV
> > tristate "DRM Support for Hyper-V synthetic video device"
> > depends on DRM && PCI && HYPERV
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> > index 4dafbdc8f86ac..32ed4cf9df1bd 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -231,6 +231,7 @@ obj-y += solomon/
> > obj-$(CONFIG_DRM_SPRD) += sprd/
> > obj-$(CONFIG_DRM_LOONGSON) += loongson/
> > obj-$(CONFIG_DRM_POWERVR) += imagination/
> > +obj-$(CONFIG_DRM_VERISILICON_DC) += verisilicon/
> >
> > # Ensure drm headers are self-contained and pass kernel-doc
> > hdrtest-files := \
> > diff --git a/drivers/gpu/drm/verisilicon/Kconfig
> > b/drivers/gpu/drm/verisilicon/Kconfig
> > new file mode 100644
> > index 0000000000000..0235577c72824
> > --- /dev/null
> > +++ b/drivers/gpu/drm/verisilicon/Kconfig
> > @@ -0,0 +1,15 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +config DRM_VERISILICON_DC
> > + tristate "DRM Support for Verisilicon DC-series display
> > controllers"
> > + depends on DRM && COMMON_CLK
> > + depends on RISCV || COMPILER_TEST
> > + select DRM_CLIENT_SELECTION
> > + select DRM_GEM_DMA_HELPER
> > + select DRM_KMS_HELPER
> > + select DRM_BRIDGE_CONNECTOR
> > + select REGMAP_MMIO
> > + select VIDEOMODE_HELPERS
> > + help
> > + Choose this option if you have a SoC with Verisilicon DC-
> > series
> > + display controllers. If M is selected, the module will be
> > called
> > + verisilicon-dc.
> > diff --git a/drivers/gpu/drm/verisilicon/Makefile
> > b/drivers/gpu/drm/verisilicon/Makefile
> > new file mode 100644
> > index 0000000000000..fd8d805fbcde1
> > --- /dev/null
> > +++ b/drivers/gpu/drm/verisilicon/Makefile
> > @@ -0,0 +1,5 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +
> > +verisilicon-dc-objs := vs_bridge.o vs_crtc.o vs_dc.o vs_drm.o
> > vs_hwdb.o vs_plane.o vs_primary_plane.o
> > +
> > +obj-$(CONFIG_DRM_VERISILICON_DC) += verisilicon-dc.o
> > diff --git a/drivers/gpu/drm/verisilicon/vs_bridge.c
> > b/drivers/gpu/drm/verisilicon/vs_bridge.c
> > new file mode 100644
> > index 0000000000000..c8caf31fac7d6
> > --- /dev/null
> > +++ b/drivers/gpu/drm/verisilicon/vs_bridge.c
> > @@ -0,0 +1,330 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2025 Icenowy Zheng <uwu@...nowy.me>
> > + */
> > +
> > +#include <linux/of.h>
> > +#include <linux/regmap.h>
> > +
> > +#include <uapi/linux/media-bus-format.h>
> > +
> > +#include <drm/drm_atomic.h>
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_bridge_connector.h>
> > +#include <drm/drm_connector.h>
> > +#include <drm/drm_encoder.h>
> > +#include <drm/drm_of.h>
> > +#include <drm/drm_print.h>
> > +#include <drm/drm_simple_kms_helper.h>
> > +
> > +#include "vs_bridge.h"
> > +#include "vs_bridge_regs.h"
> > +#include "vs_crtc.h"
> > +#include "vs_dc.h"
> > +
> > +static int vs_bridge_attach(struct drm_bridge *bridge,
> > + struct drm_encoder *encoder,
> > + enum drm_bridge_attach_flags flags)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > +
> > + return drm_bridge_attach(encoder, vbridge->next,
> > + bridge, flags);
> > +}
> > +
> > +struct vsdc_dp_format {
> > + u32 linux_fmt;
> > + bool is_yuv;
> > + u32 vsdc_fmt;
> > +};
> > +
> > +static struct vsdc_dp_format vsdc_dp_supported_fmts[] = {
> > + /* default to RGB888 */
> > + { MEDIA_BUS_FMT_FIXED, false,
> > VSDC_DISP_DP_CONFIG_FMT_RGB888 },
> > + { MEDIA_BUS_FMT_RGB888_1X24, false,
> > VSDC_DISP_DP_CONFIG_FMT_RGB888 },
> > + { MEDIA_BUS_FMT_RGB565_1X16, false,
> > VSDC_DISP_DP_CONFIG_FMT_RGB565 },
> > + { MEDIA_BUS_FMT_RGB666_1X18, false,
> > VSDC_DISP_DP_CONFIG_FMT_RGB666 },
> > + { MEDIA_BUS_FMT_RGB888_1X24, false,
> > VSDC_DISP_DP_CONFIG_FMT_RGB888 },
> > + { MEDIA_BUS_FMT_RGB101010_1X30,
> > + false, VSDC_DISP_DP_CONFIG_FMT_RGB101010 },
> > + { MEDIA_BUS_FMT_UYVY8_1X16, true,
> > VSDC_DISP_DP_CONFIG_YUV_FMT_UYVY8 },
> > + { MEDIA_BUS_FMT_UYVY10_1X20, true,
> > VSDC_DISP_DP_CONFIG_YUV_FMT_UYVY10 },
> > + { MEDIA_BUS_FMT_YUV8_1X24, true,
> > VSDC_DISP_DP_CONFIG_YUV_FMT_YUV8 },
> > + { MEDIA_BUS_FMT_YUV10_1X30, true,
> > VSDC_DISP_DP_CONFIG_YUV_FMT_YUV10 },
> > + { MEDIA_BUS_FMT_UYYVYY8_0_5X24,
> > + true, VSDC_DISP_DP_CONFIG_YUV_FMT_UYYVYY8 },
> > + { MEDIA_BUS_FMT_UYYVYY10_0_5X30,
> > + true, VSDC_DISP_DP_CONFIG_YUV_FMT_UYYVYY10 },
> > +};
> > +
> > +static u32 *vs_bridge_atomic_get_output_bus_fmts(struct drm_bridge
> > *bridge,
> > + struct drm_bridge_state
> > *bridge_state,
> > + struct drm_crtc_state
> > *crtc_state,
> > + struct drm_connector_state
> > *conn_state,
> > + unsigned int
> > *num_output_fmts)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > + struct drm_connector *conn = conn_state->connector;
> > + u32 *output_fmts;
> > + unsigned int i;
> > +
> > + if (vbridge->intf == VSDC_OUTPUT_INTERFACE_DPI)
> > + *num_output_fmts = 1;
> > + else
> > + *num_output_fmts =
> > ARRAY_SIZE(vsdc_dp_supported_fmts);
> > +
> > + output_fmts = kcalloc(*num_output_fmts,
> > sizeof(*output_fmts),
> > + GFP_KERNEL);
> > + if (!output_fmts)
> > + return NULL;
> > +
> > + if (vbridge->intf == VSDC_OUTPUT_INTERFACE_DPI) {
> > + if (conn->display_info.num_bus_formats &&
> > + conn->display_info.bus_formats)
> > + output_fmts[0] = conn-
> > >display_info.bus_formats[0];
> > + else
> > + output_fmts[0] = MEDIA_BUS_FMT_FIXED;
> > + } else {
> > + for (i = 0; i < *num_output_fmts; i++)
> > + output_fmts[i] =
> > vsdc_dp_supported_fmts[i].linux_fmt;
> > + }
> > +
> > + return output_fmts;
> > +}
> > +
> > +static bool vs_bridge_out_dp_fmt_supported(u32 out_fmt)
> > +{
> > + unsigned int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(vsdc_dp_supported_fmts); i++)
> > + if (vsdc_dp_supported_fmts[i].linux_fmt == out_fmt)
> > + break;
> > +
> > + return !(i == ARRAY_SIZE(vsdc_dp_supported_fmts));
> > +}
> > +
> > +static u32 *vs_bridge_atomic_get_input_bus_fmts(struct drm_bridge
> > *bridge,
> > + struct drm_bridge_state
> > *bridge_state,
> > + struct drm_crtc_state
> > *crtc_state,
> > + struct drm_connector_state
> > *conn_state,
> > + u32 output_fmt,
> > + unsigned int
> > *num_input_fmts)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > +
> > + if (vbridge->intf == VSDC_OUTPUT_INTERFACE_DP &&
> > + !vs_bridge_out_dp_fmt_supported(output_fmt)) {
> > + *num_input_fmts = 0;
> > + return NULL;
> > + }
> > +
> > + return drm_atomic_helper_bridge_propagate_bus_fmt(bridge,
> > bridge_state,
> > +
> > crtc_state,
> > +
> > conn_state,
> > +
> > output_fmt,
> > +
> > num_input_fmts);
> > +}
> > +
> > +static int vs_bridge_atomic_check(struct drm_bridge *bridge,
> > + struct drm_bridge_state
> > *bridge_state,
> > + struct drm_crtc_state
> > *crtc_state,
> > + struct drm_connector_state
> > *conn_state)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > +
> > + if (vbridge->intf == VSDC_OUTPUT_INTERFACE_DP &&
> > + !vs_bridge_out_dp_fmt_supported(bridge_state-
> > >output_bus_cfg.format))
> > + return -EINVAL;
> > +
> > + vbridge->output_bus_fmt = bridge_state-
> > >output_bus_cfg.format;
> > +
> > + return 0;
> > +}
> > +
> > +static void vs_bridge_atomic_enable(struct drm_bridge *bridge,
> > + struct drm_atomic_state *state)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > + struct drm_bridge_state *br_state =
> > drm_atomic_get_bridge_state(state,
> > +
> > bridge);
> > + struct vs_crtc *crtc = vbridge->crtc;
> > + struct vs_dc *dc = crtc->dc;
> > + unsigned int output = crtc->id;
> > + u32 dp_fmt;
> > + unsigned int i;
> > +
> > + DRM_DEBUG_DRIVER("Enabling output %u\n", output);
> > +
> > + switch (vbridge->intf) {
> > + case VSDC_OUTPUT_INTERFACE_DPI:
> > + regmap_clear_bits(dc->regs,
> > VSDC_DISP_DP_CONFIG(output),
> > + VSDC_DISP_DP_CONFIG_DP_EN);
> > + break;
> > + case VSDC_OUTPUT_INTERFACE_DP:
> > + for (i = 0; i < ARRAY_SIZE(vsdc_dp_supported_fmts);
> > i++) {
> > + if (vsdc_dp_supported_fmts[i].linux_fmt ==
> > + vbridge->output_bus_fmt)
> > + break;
> > + }
> > + WARN_ON_ONCE(i ==
> > ARRAY_SIZE(vsdc_dp_supported_fmts));
> > + dp_fmt = vsdc_dp_supported_fmts[i].vsdc_fmt;
> > + dp_fmt |= VSDC_DISP_DP_CONFIG_DP_EN;
> > + regmap_write(dc->regs, VSDC_DISP_DP_CONFIG(output),
> > dp_fmt);
> > + regmap_assign_bits(dc->regs,
> > + VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_YUV,
> > +
> > vsdc_dp_supported_fmts[i].is_yuv);
> > + break;
> > + }
> > +
> > + regmap_clear_bits(dc->regs, VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_DAT_POL);
> > + regmap_assign_bits(dc->regs,
> > VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_DE_POL,
> > + br_state->output_bus_cfg.flags &
> > + DRM_BUS_FLAG_DE_LOW);
> > + regmap_assign_bits(dc->regs,
> > VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_CLK_POL,
> > + br_state->output_bus_cfg.flags &
> > + DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE);
> > + regmap_set_bits(dc->regs, VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_DE_EN |
> > + VSDC_DISP_PANEL_CONFIG_DAT_EN |
> > + VSDC_DISP_PANEL_CONFIG_CLK_EN);
> > + regmap_set_bits(dc->regs, VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_RUNNING);
> > + regmap_clear_bits(dc->regs, VSDC_DISP_PANEL_START,
> > + VSDC_DISP_PANEL_START_MULTI_DISP_SYNC);
> > + regmap_set_bits(dc->regs, VSDC_DISP_PANEL_START,
> > + VSDC_DISP_PANEL_START_RUNNING(output));
> > +
> > + regmap_set_bits(dc->regs, VSDC_DISP_PANEL_CONFIG_EX(crtc-
> > >id),
> > + VSDC_DISP_PANEL_CONFIG_EX_COMMIT);
> > +}
> > +
> > +static void vs_bridge_atomic_disable(struct drm_bridge *bridge,
> > + struct drm_atomic_state
> > *state)
> > +{
> > + struct vs_bridge *vbridge =
> > drm_bridge_to_vs_bridge(bridge);
> > + struct vs_crtc *crtc = vbridge->crtc;
> > + struct vs_dc *dc = crtc->dc;
> > + unsigned int output = crtc->id;
> > +
> > + DRM_DEBUG_DRIVER("Disabling output %u\n", output);
> > +
> > + regmap_clear_bits(dc->regs, VSDC_DISP_PANEL_START,
> > + VSDC_DISP_PANEL_START_MULTI_DISP_SYNC |
> > + VSDC_DISP_PANEL_START_RUNNING(output));
> > + regmap_clear_bits(dc->regs, VSDC_DISP_PANEL_CONFIG(output),
> > + VSDC_DISP_PANEL_CONFIG_RUNNING);
> > +
> > + regmap_set_bits(dc->regs, VSDC_DISP_PANEL_CONFIG_EX(crtc-
> > >id),
> > + VSDC_DISP_PANEL_CONFIG_EX_COMMIT);
> > +}
> > +
> > +static const struct drm_bridge_funcs vs_bridge_funcs = {
> > + .attach = vs_bridge_attach,
> > + .atomic_enable = vs_bridge_atomic_enable,
> > + .atomic_disable = vs_bridge_atomic_disable,
> > + .atomic_check = vs_bridge_atomic_check,
> > + .atomic_get_input_bus_fmts =
> > vs_bridge_atomic_get_input_bus_fmts,
> > + .atomic_get_output_bus_fmts =
> > vs_bridge_atomic_get_output_bus_fmts,
> > + .atomic_duplicate_state =
> > drm_atomic_helper_bridge_duplicate_state,
> > + .atomic_destroy_state =
> > drm_atomic_helper_bridge_destroy_state,
> > + .atomic_reset = drm_atomic_helper_bridge_reset,
> > +};
> > +
> > +static int vs_bridge_detect_output_interface(struct device_node
> > *of_node,
> > + unsigned int output)
> > +{
> > + int ret;
> > + struct device_node *remote;
> > +
> > + remote = of_graph_get_remote_node(of_node, output,
> > +
> > VSDC_OUTPUT_INTERFACE_DPI);
> > + if (remote) {
> > + ret = VSDC_OUTPUT_INTERFACE_DPI;
> > + } else {
> > + remote = of_graph_get_remote_node(of_node, output,
> > +
> > VSDC_OUTPUT_INTERFACE_DP);
> > + if (remote)
> > + ret = VSDC_OUTPUT_INTERFACE_DP;
> > + else
> > + ret = -ENODEV;
> > + }
> > +
> > + return ret;
> > +}
> > +
> > +struct vs_bridge *vs_bridge_init(struct drm_device *drm_dev,
> > + struct vs_crtc *crtc)
> > +{
> > + unsigned int output = crtc->id;
> > + struct vs_bridge *bridge;
> > + struct drm_bridge *next;
> > + enum vs_bridge_output_interface intf;
> > + int ret;
> > +
> > + intf = vs_bridge_detect_output_interface(drm_dev->dev-
> > >of_node,
> > + output);
> > + if (intf == -ENODEV) {
> > + dev_info(drm_dev->dev, "Skipping output %u\n",
> > output);
> > + return NULL;
> > + }
> > +
> > + bridge = devm_kzalloc(drm_dev->dev, sizeof(*bridge),
> > GFP_KERNEL);
> > + if (!bridge)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + bridge->crtc = crtc;
> > + bridge->intf = intf;
> > + bridge->base.funcs = &vs_bridge_funcs;
>
> So I am trying to make it work on JH7110 as well, and here is the
> problem:
>
> [ 5.564433] ------------[ cut here ]------------
>
>
> [ 5.569161] refcount_t: addition on 0; use-after-
> free.
>
> [ 5.574485] WARNING: CPU: 2 PID: 71 at lib/refcount.c:25
> refcount_warn_saturate+0x110/0x162
>
> [ 5.574537] Modules linked
> in:
>
>
> [ 5.574560] CPU: 2 UID: 0 PID: 71 Comm: kworker/u17:2 Not tainted
> 6.17.0-rc1-g60ec647ec20c-dirty #77
> NONE
>
> [ 5.574596] Hardware name: StarFive VisionFive 2 v1.2A
> (DT)
>
> [ 5.574613] Workqueue: events_unbound
> deferred_probe_work_func
>
>
> [ 5.574654] epc :
> refcount_warn_saturate+0x110/0x162
>
>
> [ 5.574682] ra :
> refcount_warn_saturate+0x110/0x162
>
>
> [ 5.574710] epc : ffffffff81336608 ra : ffffffff81336608 sp :
> ffffffc6006e7530
>
> [ 5.574732] gp : ffffffff8514c1c0 tp : ffffffd6c14ba580 t0 :
> ffffffc6006e7134
>
> [ 5.574753] t1 : fffffffef0a29898 t2 : 5f746e756f636665 s0 :
> ffffffc6006e7550
>
> [ 5.574774] s1 : ffffffff83c058a8 a0 : 000000000000002a a1 :
> 0000000000000004
>
> [ 5.574794] a2 : 0000000000000000 a3 : ffffffff801ef586 a4 :
> 0000000000000000
>
> [ 5.574813] a5 : 0000000000000000 a6 : fffffffef0a29899 a7 :
> 0000000000000003
>
> [ 5.574833] s2 : ffffffd6c35e68e8 s3 : ffffffd6c35e6990 s4 :
> ffffffd6c33dc008
>
> [ 5.574854] s5 : 0000000000000000 s6 : 1ffffffad867b801 s7 :
> 0000000000000000
>
> [ 5.574873] s8 : ffffffd6c35e6990 s9 : 0000000000000000 s10:
> ffffffd6c3099058
>
> [ 5.574894] s11: 1ffffffad861320b t3 : 1ffffff8c00dce34 t4 :
> fffffffef0a29898
>
> [ 5.574915] t5 : fffffffef0a29899 t6 :
> ffffffc6006e6f38
>
>
> [ 5.574933] status: 0000000200000120 badaddr: 0000000000000000
> cause:
> 0000000000000003
>
> [ 5.574952] [<ffffffff81336608>]
> refcount_warn_saturate+0x110/0x162
>
>
> [ 5.574985] [<ffffffff8193a506>]
> drm_bridge_get+0x66/0x6e
>
>
> [ 5.575022] [<ffffffff8001f26e>]
> drm_bridge_attach+0x54/0x5a2
>
>
> [ 5.575055] [<ffffffff8002740e>]
> vs_bridge_init+0x3bc/0x4ba
>
>
> [ 5.575087] [<ffffffff82313026>]
> vs_drm_initialize+0xe0/0x2f2
>
>
> [ 5.575126] [<ffffffff80027ca4>]
> vs_dc_probe+0x758/0x85c
>
>
> [ 5.575156] [<ffffffff8233123c>]
> platform_probe+0xac/0x138
>
>
> [ 5.575186] [<ffffffff8232b2a8>]
> really_probe+0x164/0x59e
>
>
> [ 5.575221] [<ffffffff8232b818>] __driver_probe_device+0x136/0x266
> [ 5.575257] [<ffffffff8232bb18>] driver_probe_device+0x56/0x214
> [ 5.575292] [<ffffffff8232bdf0>]
> __device_attach_driver+0x11a/0x278
> [ 5.575329] [<ffffffff823272d8>] bus_for_each_drv+0xea/0x16e
> [ 5.575363] [<ffffffff8232c680>] __device_attach+0x160/0x2d4
> [ 5.575398] [<ffffffff8232ca06>] device_initial_probe+0xe/0x16
> [ 5.575434] [<ffffffff823291d8>] bus_probe_device+0xfe/0x134
> [ 5.575468] [<ffffffff82329c62>]
> deferred_probe_work_func+0x128/0x1d6
> [ 5.575503] [<ffffffff80126aae>] process_one_work+0x5c0/0xe76
> [ 5.575543] [<ffffffff80129da6>] worker_thread+0x6d4/0x1316
> [ 5.575572] [<ffffffff801429ce>] kthread+0x29a/0x570
> [ 5.575608] [<ffffffff8004693e>] ret_from_fork_kernel+0x10/0x9a
> [ 5.575643] [<ffffffff835f55f6>]
> ret_from_fork_kernel_asm+0x16/0x18
> [ 5.575682] ---[ end trace 0000000000000000 ]---
>
>
> When a bridge is allocated with kzalloc, its kref count is
> initialized
> to zero. The drm_bridge_attach() function then calls drm_bridge_get()
> on
> this bridge, which sees the zero refcount and triggers a use-after-
> free
> warning because it assumes the object has already been freed.
>
> To fix this, the bridge's refcount must be initialized with
> kref_init()
> after allocation and before it's attached.
This is going to be changed to devm_drm_bridge_alloc() in the next
revision.
>
> > +
> > + next = devm_drm_of_get_bridge(drm_dev->dev, drm_dev->dev-
> > >of_node,
> > + output, intf);
> > + if (IS_ERR(next)) {
> > + ret = PTR_ERR(next);
> > + goto err_free_bridge;
> > + }
> > +
> > + bridge->next = next;
> > +
> > + ret = drm_simple_encoder_init(drm_dev, &bridge->enc,
> > + (intf ==
> > VSDC_OUTPUT_INTERFACE_DPI) ?
> > + DRM_MODE_ENCODER_DPI :
> > + DRM_MODE_ENCODER_NONE);
> > + if (ret) {
> > + dev_err(drm_dev->dev,
> > + "Cannot initialize encoder for output
> > %u\n", output);
> > + goto err_free_bridge;
> > + }
> > +
> > + bridge->enc.possible_crtcs = drm_crtc_mask(&crtc->base);
> > +
> > + ret = drm_bridge_attach(&bridge->enc, &bridge->base, NULL,
> > + DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> > + if (ret) {
> > + dev_err(drm_dev->dev,
> > + "Cannot attach bridge for output %u\n",
> > output);
> > + goto err_cleanup_encoder;
> > + }
> > +
> > + bridge->conn = drm_bridge_connector_init(drm_dev, &bridge-
> > >enc);
> > + if (IS_ERR(bridge->conn)) {
> > + dev_err(drm_dev->dev,
> > + "Cannot create connector for output %u\n",
> > output);
> > + ret = PTR_ERR(bridge->conn);
> > + goto err_cleanup_encoder;
> > + }
> > + drm_connector_attach_encoder(bridge->conn, &bridge->enc);
> > +
> > + return bridge;
> > +
> > +err_cleanup_encoder:
> > + drm_encoder_cleanup(&bridge->enc);
> > +err_free_bridge:
> > + devm_kfree(drm_dev->dev, bridge);
> > +
> > + return ERR_PTR(ret);
> > +}
>
>
> Best regards,
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