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Message-ID: <5e9aad79-fef1-4258-83c4-6938ceafbaa5@huawei.com>
Date: Tue, 23 Sep 2025 10:57:56 +0800
From: Yongbang Shi <shiyongbang@...wei.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.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>,
<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
<shiyongbang@...wei.com>
Subject: Re: [PATCH v6 drm-dp 1/4] drm/hisilicon/hibmc: fix dp probabilistical
detect errors after HPD irq
> On Mon, Sep 22, 2025 at 10:49:40AM +0800, Yongbang Shi wrote:
>> From: Baihan Li <libaihan@...wei.com>
>>
>> The issue is that drm_connector_helper_detect_from_ddc() returns wrong
>> status when plugging or unplugging the monitor. Use HPD pin status in
>> DP's detect_ctx() for real physcal monitor in/out, and keep using
>> detect_frome_ddc() if it's the first time to call detect because of
>> insmoding driver.
> If I understand correct, this is not quite right. Consider DP-to-HDMI or
> DP-to-DVI dongle being plugged without an actual monitor and then the
> monitor being plugged later on.
Hi Dmitry,
Thanks for your correction. So your point is that if the HPD comes in from a dongle.
Is that okay to add those checks at the end?
ret = drm_dp_read_dpcd_caps(dp_dev->aux, dp_dev->dpcd);
if (ret)
return connector_status_disconnected;
if (!drm_dp_is_branch(dpcd))
return connector_status_connected;
if (drm_dp_read_sink_count_cap(connector, dp_dev->dpcd, &dp_dev->desc) &&
dp_dev->dpcd[DP_DOWNSTREAM_PORT_0] & DP_DS_PORT_HPD) {
ret = drm_dp_read_sink_count(dp_dev->dpcd);
if (ret > 0)
return connector_status_connected;
}
Thanks，
Baihan
>> Fixes: 3c7623fb5bb6 ("drm/hisilicon/hibmc: Enable this hot plug detect of irq feature")
>> Signed-off-by: Baihan Li <libaihan@...wei.com>
>> Signed-off-by: Yongbang Shi <shiyongbang@...wei.com>
>> ---
>> ChangeLog:
>> v5 -> v6:
>> - use HPD status in DP detect_ctx(), suggested by Dmitry Baryshkov.
>> v4 -> v5:
>> - fix the commit message and DP detect_ctx(), suggested by Dmitry Baryshkov.
>> ---
>> drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c | 12 ++++++++++++
>> drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h | 7 +++++++
>> drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h | 3 +++
>> drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c | 13 +++++++++++--
>> 4 files changed, 33 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
>> index 8f0daec7d174..4d8d3e4d4f84 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
>> @@ -2,6 +2,7 @@
>> // Copyright (c) 2024 Hisilicon Limited.
>>
>> #include <linux/io.h>
>> +#include <linux/iopoll.h>
>> #include <linux/delay.h>
>> #include "dp_config.h"
>> #include "dp_comm.h"
>> @@ -305,3 +306,14 @@ void hibmc_dp_set_cbar(struct hibmc_dp *dp, const struct hibmc_dp_cbar_cfg *cfg)
>> hibmc_dp_reg_write_field(dp_dev, HIBMC_DP_COLOR_BAR_CTRL, BIT(0), cfg->enable);
>> writel(HIBMC_DP_SYNC_EN_MASK, dp_dev->base + HIBMC_DP_TIMING_SYNC_CTRL);
>> }
>> +
>> +void hibmc_dp_update_hpd_status(struct hibmc_dp *dp)
>> +{
>> + int status;
>> +
>> + readl_poll_timeout(dp->dp_dev->base + HIBMC_DP_HPD_STATUS, status,
>> + FIELD_GET(HIBMC_DP_HPD_CUR_STATE, status) != dp->hpd_status,
>> + 1000, 100000); /* DP spec says 100ms */
>> +
>> + dp->hpd_status = FIELD_GET(HIBMC_DP_HPD_CUR_STATE, status);
>> +}
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
>> index 665f5b166dfb..8348ad9e34a8 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
>> @@ -14,6 +14,11 @@
>>
>> struct hibmc_dp_dev;
>>
>> +enum hibmc_hpd_status {
>> + HIBMC_HPD_OUT,
>> + HIBMC_HPD_IN,
>> +};
>> +
>> enum hibmc_dp_cbar_pattern {
>> CBAR_COLOR_BAR,
>> CBAR_WHITE,
>> @@ -50,6 +55,7 @@ struct hibmc_dp {
>> struct drm_dp_aux aux;
>> struct hibmc_dp_cbar_cfg cfg;
>> u32 irq_status;
>> + int hpd_status;
>> };
>>
>> int hibmc_dp_hw_init(struct hibmc_dp *dp);
>> @@ -60,5 +66,6 @@ void hibmc_dp_reset_link(struct hibmc_dp *dp);
>> void hibmc_dp_hpd_cfg(struct hibmc_dp *dp);
>> void hibmc_dp_enable_int(struct hibmc_dp *dp);
>> void hibmc_dp_disable_int(struct hibmc_dp *dp);
>> +void hibmc_dp_update_hpd_status(struct hibmc_dp *dp);
>>
>> #endif
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
>> index 394b1e933c3a..64306abcd986 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
>> @@ -24,6 +24,9 @@
>> #define HIBMC_DP_CFG_AUX_READY_DATA_BYTE GENMASK(16, 12)
>> #define HIBMC_DP_CFG_AUX GENMASK(24, 17)
>>
>> +#define HIBMC_DP_HPD_STATUS 0x98
>> +#define HIBMC_DP_HPD_CUR_STATE GENMASK(7, 4)
>> +
>> #define HIBMC_DP_PHYIF_CTRL0 0xa0
>> #define HIBMC_DP_CFG_SCRAMBLE_EN BIT(0)
>> #define HIBMC_DP_CFG_PAT_SEL GENMASK(7, 4)
>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> index d06832e62e96..48c9c97eef0e 100644
>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
>> @@ -34,9 +34,16 @@ static int hibmc_dp_connector_get_modes(struct drm_connector *connector)
>> static int hibmc_dp_detect(struct drm_connector *connector,
>> struct drm_modeset_acquire_ctx *ctx, bool force)
>> {
>> - mdelay(200);
>> + struct hibmc_dp *dp = to_hibmc_dp(connector);
>> +
>> + /* if no HPD just probe DDC */
>> + if (!dp->irq_status)
>> + return drm_connector_helper_detect_from_ddc(connector, ctx, force);
>>
>> - return drm_connector_helper_detect_from_ddc(connector, ctx, force);
>> + if (dp->hpd_status == HIBMC_HPD_IN)
>> + return connector_status_connected;
>> +
>> + return connector_status_disconnected;
>> }
>>
>> static const struct drm_connector_helper_funcs hibmc_dp_conn_helper_funcs = {
>> @@ -128,6 +135,8 @@ irqreturn_t hibmc_dp_hpd_isr(int irq, void *arg)
>> hibmc_dp_reset_link(&priv->dp);
>> }
>>
>> + hibmc_dp_update_hpd_status(&priv->dp);
>> +
>> if (dev->registered)
>> drm_connector_helper_hpd_irq_event(&priv->dp.connector);
>>
>> --
>> 2.33.0
>>
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