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Message-ID: <tqbbkhod5et6yxyfhzmgelborrhwjaazk6ylkw3srlqmmkp6ou@jefvdyktsuds>
Date: Sat, 26 Jul 2025 19:03:23 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yongbang Shi <shiyongbang@...wei.com>
Cc: xinliang.liu@...aro.org, tiantao6@...ilicon.com,
maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
kong.kongxinwei@...ilicon.com, liangjian010@...wei.com,
chenjianmin@...wei.com, fengsheng5@...wei.com, libaihan@...wei.com,
shenjian15@...wei.com, shaojijie@...wei.com,
jani.nikula@...ux.intel.com, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 drm-dp 08/11] drm/hisilicon/hibmc: fix no showing when
no connectors connected
On Fri, Jul 18, 2025 at 02:51:22PM +0800, Yongbang Shi wrote:
> From: Baihan Li <libaihan@...wei.com>
>
> Our chip support KVM over IP feature, so hibmc diiver need to support
I assume that KVM-over-IP doesnt provide EDID reads. This needs to be
stated in the commit message.
> displaying without any connectors plugged in. If no connectors connected,
> set the vdac connector status to 'connected' to handle BMC KVM. Use
> is_connected to check all physical outputs.
> For get_modes: using BMC modes for connector if no display is attached to
> phys VGA cable, otherwise use EDID modes by drm_connector_helper_get_modes.
>
> Fixes: 4c962bc929f1 ("drm/hisilicon/hibmc: Add vga connector detect functions")
> Signed-off-by: Baihan Li <libaihan@...wei.com>
> Signed-off-by: Yongbang Shi <shiyongbang@...wei.com>
> ---
> ChangeLog:
> v2 -> v3:
> - fix hibmc_connector_get_modes() and hibmc_vdac_detect() to realize BMC KVM, suggested by Dmitry Baryshkov.
> ---
> .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c | 5 +-
> .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h | 4 ++
> .../gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c | 55 +++++++++++++------
> 3 files changed, 45 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
> index 99b30a6c7e06..262ebe6138f0 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
> @@ -58,9 +58,12 @@ static int hibmc_dp_detect(struct drm_connector *connector,
> {
> struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
>
> - if (!hibmc_dp_detect_link(&priv->dp))
> + if (!hibmc_dp_detect_link(&priv->dp)) {
> + priv->is_connected |= BIT(0);
Magic value BIT(0)
> return connector_status_connected;
> + }
>
> + priv->is_connected &= ~BIT(0);
> return connector_status_disconnected;
> }
>
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
> index ca8502e2760c..d68588ecec9b 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h
> @@ -31,6 +31,7 @@ struct hibmc_vdac {
> struct drm_connector connector;
> struct i2c_adapter adapter;
> struct i2c_algo_bit_data bit_data;
> + int phys_status;
> };
>
> struct hibmc_drm_private {
> @@ -43,6 +44,9 @@ struct hibmc_drm_private {
> struct drm_crtc crtc;
> struct hibmc_vdac vdac;
> struct hibmc_dp dp;
> +
> + /* VGA and DP phys connect status, BIT(0) is DP, BIT(1) is VGA */
#define those.
> + int is_connected;
And you need a lock around this one, otherwise you might get a race
between DP's and VGA's code setting and clearing bits here.
> };
>
> static inline struct hibmc_vdac *to_hibmc_vdac(struct drm_connector *connector)
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> index 841e81f47b68..3cdf640d1785 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_vdac.c
> @@ -25,27 +25,18 @@
> static int hibmc_connector_get_modes(struct drm_connector *connector)
> {
> struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
> - const struct drm_edid *drm_edid;
> int count;
>
> - drm_edid = drm_edid_read_ddc(connector, &vdac->adapter);
> -
> - drm_edid_connector_update(connector, drm_edid);
> -
> - if (drm_edid) {
> - count = drm_edid_connector_add_modes(connector);
> - if (count)
> - goto out;
> + if (vdac->phys_status == connector_status_connected) {
> + count = drm_connector_helper_get_modes(connector);
> + } else {
> + drm_edid_connector_update(connector, NULL);
> + count = drm_add_modes_noedid(connector,
> + connector->dev->mode_config.max_width,
> + connector->dev->mode_config.max_height);
> + drm_set_preferred_mode(connector, 1024, 768); // 1024x768
> }
>
> - count = drm_add_modes_noedid(connector,
> - connector->dev->mode_config.max_width,
> - connector->dev->mode_config.max_height);
> - drm_set_preferred_mode(connector, 1024, 768);
> -
> -out:
> - drm_edid_free(drm_edid);
> -
> return count;
> }
>
> @@ -57,10 +48,38 @@ static void hibmc_connector_destroy(struct drm_connector *connector)
> drm_connector_cleanup(connector);
> }
>
> +static int hibmc_vdac_detect(struct drm_connector *connector,
> + struct drm_modeset_acquire_ctx *ctx,
> + bool force)
> +{
> + struct hibmc_drm_private *priv = to_hibmc_drm_private(connector->dev);
> + struct hibmc_vdac *vdac = to_hibmc_vdac(connector);
> + enum drm_connector_status status;
> +
> + status = drm_connector_helper_detect_from_ddc(connector, ctx, force);
> +
> + vdac->phys_status = status;
> +
> + if (status == connector_status_connected) {
> + priv->is_connected |= BIT(1);
> + return connector_status_connected;
> + }
> +
> + priv->is_connected &= ~BIT(1);
> +
> + /* if all connectors are disconnected,
> + * return connected to support BMC KVM display.
> + */
> + if (!priv->is_connected)
> + return connector_status_connected;
> +
> + return connector_status_disconnected;
> +}
> +
> static const struct drm_connector_helper_funcs
> hibmc_connector_helper_funcs = {
> .get_modes = hibmc_connector_get_modes,
> - .detect_ctx = drm_connector_helper_detect_from_ddc,
> + .detect_ctx = hibmc_vdac_detect,
> };
>
> static const struct drm_connector_funcs hibmc_connector_funcs = {
> --
> 2.33.0
>
--
With best wishes
Dmitry
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