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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39668a5832bsm3060969a91.15.2026.08.26.00.48.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Aug 2026 00:48:44 -0700 (PDT) Message-ID: <96bc9f2d-a0a4-40f5-8281-55c6f9982559@oss.qualcomm.com> Date: Wed, 26 Aug 2026 15:48:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND v5 15/25] drm/msm/dp: add an API to initialize MST on sink side To: Dmitry Baryshkov Cc: Rob Clark , Dmitry Baryshkov , Abhinav Kumar , Sean Paul , Marijn Suijten , David Airlie , Simona Vetter , Jessica Zhang , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, Abhinav Kumar References: <20260629-msm-dp-mst-v5-0-2ed6aee1867a@oss.qualcomm.com> <20260629-msm-dp-mst-v5-15-2ed6aee1867a@oss.qualcomm.com> Content-Language: en-US From: Yongxing Mou In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=EMA2FVZC c=1 sm=1 tr=0 ts=6a8e9a5e cx=c_pps a=0uOsjrqzRL749jD1oC5vDA==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=COk6AnOGAAAA:8 a=EUspDBNiAAAA:8 a=tepjUtBTXmVVZiRr_ggA:9 a=QEXdDO2ut3YA:10 a=mQ_c8vxmzFEMiUWkPHU9:22 a=TjNXssC_j7lpFel5tvFf:22 X-Proofpoint-ORIG-GUID: e5OVdHMEs7yv6WwM2eaRpNGv90aEO5ZF X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI2MDA2MyBTYWx0ZWRfXx8NPbgC4jYNB rs5OF2zh7pFIu6gkGHKiJRISw7/ycGlciGixJNGgLswmFKI6e0xtslTlLDBVr9pHYhnJ23lU1ht Iu3puRZ7RdKpflwBE5OPyvVlqAvvu5LuP52hX+OYUilYXWWWgseGt/Xo86PLdqeRVsFHtg1UhvC FH8aHwQ7bf03ezsWOriGZQdIeScqvPSIs0lCS7DJLF+BD24SNcdcRCuEwx78QfhefzxVtBYwriO DBG+2zml35yPwq36RWGesKjF00xt4QNSU2IEwqlTtsoc0CuyA745Y+x6VKxYRRqg3pB6OatJXti aG1ewD+FS5JL3llY0BqiUTPx3G2cmq9YzG2xK/nFZtzWN47VqmdonAJkyOUGmu06pWQXab3gmbC yPUvLAGbjSuGleb/olKc/8TTtgqAGfMGFLCjk9ubLga8yM1UUbDssOYEWzEAxL6ybEzSmfIgmq2 0xhdhYqcEIBAqQ6IZoQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwODI2MDA2MyBTYWx0ZWRfX0pzUh8p38f0n nJuyeivh82sPEwUAe4bIYSqBDouce8Or3wIRcsyq3lNy5bJcG9bHzp4gO43FK7/Xgij9ljhq+QO NyBkgNYVJq3K8c8v64WZUa+uGEep4BQ= X-Proofpoint-GUID: e5OVdHMEs7yv6WwM2eaRpNGv90aEO5ZF X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-26_02,2026-08-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 malwarescore=0 clxscore=1015 phishscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608260063 On 7/13/2026 5:35 AM, Dmitry Baryshkov wrote: > On Mon, Jun 29, 2026 at 10:14:36PM +0800, Yongxing Mou wrote: >> From: Abhinav Kumar >> >> If the DP controller is capable of supporting multiple streams >> then initialize the DP sink in MST mode by programming the DP_MSTM_CTRL >> DPCD register to enable MST mode. >> >> Signed-off-by: Abhinav Kumar >> Signed-off-by: Yongxing Mou >> --- >> drivers/gpu/drm/msm/dp/dp_display.c | 48 +++++++++++++++++++++++++++++++------ >> 1 file changed, 41 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c >> index 5786e598a406..c3be656f10ee 100644 >> --- a/drivers/gpu/drm/msm/dp/dp_display.c >> +++ b/drivers/gpu/drm/msm/dp/dp_display.c >> @@ -14,6 +14,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> #include "msm_drv.h" >> @@ -270,6 +271,31 @@ static int msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd >> return lttpr_count; >> } >> >> +static void msm_dp_display_mst_init(struct msm_dp_display_private *dp) >> +{ >> + u8 old_mstm_ctrl; >> + struct msm_dp *msm_dp = &dp->msm_dp_display; >> + int ret; >> + >> + /* clear sink MST state */ >> + drm_dp_dpcd_read_byte(dp->aux, DP_MSTM_CTRL, &old_mstm_ctrl); >> + >> + ret = drm_dp_dpcd_write_byte(dp->aux, DP_MSTM_CTRL, 0); >> + if (ret < 0) { >> + DRM_ERROR("failed to clear DP_MSTM_CTRL, ret=%d\n", ret); >> + return; >> + } > > Is it not enough to write the new value? Please add a small comment, > why (reference DP standard in the commit message, please). > Got it. >> + >> + ret = drm_dp_dpcd_write_byte(dp->aux, DP_MSTM_CTRL, >> + DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC); >> + if (ret < 0) { >> + DRM_ERROR("sink MST enablement failed\n"); >> + return; >> + } >> + >> + msm_dp->mst_active = true; >> +} >> + >> static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp) >> { >> struct drm_connector *connector = dp->msm_dp_display.connector; >> @@ -288,14 +314,19 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp) >> if (rc) >> goto end; >> >> - drm_edid = drm_edid_read_ddc(connector, &dp->aux->ddc); >> - drm_edid_connector_update(connector, drm_edid); >> + if (!(dp->max_stream > 1) || !drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) { >> + drm_edid = drm_edid_read_ddc(connector, &dp->aux->ddc); >> + drm_edid_connector_update(connector, drm_edid); >> >> - if (!drm_edid) { >> - DRM_ERROR("panel edid read failed\n"); >> - /* check edid read fail is due to unplug */ >> - if (!msm_dp_aux_is_link_connected(dp->aux)) >> - return -ETIMEDOUT; >> + if (!drm_edid) { >> + DRM_ERROR("panel edid read failed\n"); >> + /* check edid read fail is due to unplug */ >> + if (!msm_dp_aux_is_link_connected(dp->aux)) >> + return -ETIMEDOUT; >> + } >> + >> + if (rc) >> + goto end; > > This also is going to break DP. If you are using dp->max_streams as a > determining factor, rearrange commits so that max_streams are parseed > and set only after the rest of the commits are in place (and the driver > is ready for DP MST). > Sorry, that was an oversight. Those two lines shouldn't be there. The patch wasn't clean enough, and I'll remove them in the next revision. >> } >> >> msm_dp_link_process_request(dp->link); >> @@ -317,6 +348,9 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp) >> */ >> msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false); >> >> + if (dp->max_stream > 1 && drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) >> + msm_dp_display_mst_init(dp); >> + >> msm_dp_link_reset_phy_params_vx_px(dp->link); >> >> end: >> >> -- >> 2.43.0 >> >