Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v4 29/78] drm/vc4: crtc: Add a delay after disabling the
 PixelValve output
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     Tim Gover <tim.gover@raspberrypi.com>,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        LKML <linux-kernel@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Eric Anholt <eric@anholt.net>,
        bcm-kernel-feedback-list@broadcom.com,
        linux-arm-kernel@lists.infradead.org,
        Phil Elwell <phil@raspberrypi.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        linux-rpi-kernel@lists.infradead.org
References: <cover.7a1aa1784976093af26cb31fd283cf5b3ed568bb.1594230107.git-series.maxime@cerno.tech>
 <a1f22aadc60a2f32022831a6348c8bbd6e1954c3.1594230107.git-series.maxime@cerno.tech>
 <CAPY8ntBLWrfagZ5-kQz+5Mkw4_KaaTP63_L3D4owJAfA5kFpzw@mail.gmail.com>
 <20200729144251.us6a2pgkjjmm53ov@gilmour.lan>
 <ff6eca99-d98e-5b50-8b74-bba82928dda2@i2se.com>
 <20200825150606.utlynhzo664bwksy@gilmour.lan>
 <b41b066a-2d23-8ac3-be0a-c686f3954284@i2se.com>
 <20200901095829.64a5hjghf3mlsyvo@gilmour.lan>
From:   Stefan Wahren <stefan.wahren@i2se.com>
Autocrypt: addr=stefan.wahren@i2se.com; keydata=
 LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tClZlcnNpb246IEdudVBHIHYy
 CgptUUlOQkZ0NmdCTUJFQUN1Yi9wQmV2SHhidkplZnlaRzMySklObW4yYnNFUFgyNVY2ZmVq
 bXlZd21DR0tqRnRMCi9Eb1VNRVZIRHhDSjQ3Qk1YbzM0NGZIVjFDM0FudWRnTjFCZWhMb0J0
 TEh4bW5lQ3pnSDNLY1B0V1c3cHRqNEcKdEp2OUNRRFp5MjdTS29FUHh5YUk4Q0YweWdSeEpj
 NzJNOUk5d21zUFo1YlVIc0x1WVdNcVE3SmNSbVBzNkQ4ZwpCa2srOC95bmdFeU5FeHd4SnBS
 MXlsajVianhXREh5WVF2dUo1THpaS3VPOUxCM2xYVnNjNGJxWEVqYzZWRnVaCkZDQ2svc3lp
 by9ZaHNlOE4rUXN4N01RYWd6NHdLVWtRUWJmWGcxVnFrVG5BaXZYczQyVm5Ja211NWd6SXcv
 MHQKUkp2NTBGUmhIaHhweUtBSThCOG5oTjhRdng3TVZrUGM1dkRmZDN1R1lXNDdKUGhWUUJj
 VXdKd05rLzQ5RjllQQp2ZzJtdE1QRm5GT1JrV1VSdlArRzZGSmZtNitDdk92N1lmUDF1ZXdB
 aTRsbitKTzFnK2dqVklXbC9XSnB5MG5UCmlwZGZlSDlkSGtnU2lmUXVuWWN1Y2lzTXlvUmJG
 OTU1dENna0VZOUVNRWRZMXQ4aUdEaUNnWDZzNTBMSGJpM2sKNDUzdWFjcHhmUVhTYUF3UGtz
 bDhNa0NPc3YyZUVyNElOQ0hZUUR5WmljbEJ1dUNnOEVOYlI2QUdWdFpTUGNRYgplbnpTektS
 Wm9POUNhcUlEK2ZhdkxpQi9kaHptSEErOWJnSWhtWGZ2WFJMRFp6ZThwbzFkeXQzRTFzaFhp
 ZGRaClBBOE51SlZ6RUl0MmxtSTZWOHBaRHBuMjIxcmZLaml2UlFpYW9zNTRUZ1pqak1ZSTdu
 bko3ZTZ4endBUkFRQUIKdENCVGRHVm1ZVzRnVjJGb2NtVnVJRHgzWVdoeVpXNXpkRUJuYlhn
 dWJtVjBQb2tDTndRVEFRZ0FJUVVDWElkYwo0Z0liQXdVTENRZ0hBZ1lWQ0FrS0N3SUVGZ0lE
 QVFJZUFRSVhnQUFLQ1JDVWdld1BFWkR5MjFPVEQvOUdpWkxkCnRSWWNteVJKZ2x0aVFRekFp
 UWRjSUQ3OGxHb1dwL3grci92Y1U2YjZqdVl1ZVR3Z1Iwclc3djdsMklSQnlEN24KSEp4YSt0
 SVNvUVpCZ2hvbE1JZmI5TXRoR09KTENZNzdrL1FoQWhuMzJOR1prZWp3OXR6a3MvNDBtclpT
 VVQ4NApaeWJzUVhyTE0vSFI2VElJL0RlUEIwbktEM0ppcHBzMlVIUUQ5cUQySWpFd1NRUGxI
 akNPckVaaDQ1UFo3bTkrClo5M0x6aVRlc1dabFlRdUxpSndzNHJLcHRIVzFkL3dSZWxzaG1t
 NlFxY0wybDRDL2U0MGVEQjlncTRkU1poOVgKUEVZbGxpeU5RaDdhMkxTZHVtRTFyK2NTd0lq
 RS91ZHRSdmRPOWFLb0psT2JVSzVkTmpTUEg3d0tUYndkWGRZRApHUHdEaFhkNThOQXdyK1BY
 QmxQajB0STFMQ3ErTEJ4ZUt6aFdYK0dWcTlEb2pWanlVREV4Rk5Ga1h1b0M3ZzhtClY5VDB0
 ZUJpdVpSbm91WEt3VjJGcHRaT0hIN0JVRVd0a0t0aGgxZXRmT1dwaWdCemtVN2JQc2ZJWVQr
 cnk5dGIKMW9KK3Y0MVBOYXFaRW1QVXBKeHZmek5UN3Ayd01lRDdaajlmMHJ1YlJQdExBSjJR
 R2pyRkhzdVh3QU9xcHl6ZQoxOEVidHNZazBOMHp1SEVoY2orUEJJQmZoMFlJWWQ1MW9mNkdJ
 aU95UjlxMFhYdHBsVUo3VDIvSDF1UXFrWGxwCitnVzRWa2lmc2NJckl1eWZueFpXMTJlSXZq
 NnlicVdMN2FZS0dZbVQ2aUxDUGJIWXlZY2F5bDRFa0ZjckNGN0UKZTBXVC9zY1ZNaE8vNVgv
 SGFOQTVIQngvcjUycGdMY3Y0aTlNeExRbVUzUmxabUZ1SUZkaGFISmxiaUE4YzNSbApabUZ1
 TG5kaGFISmxia0JwTW5ObExtTnZiVDZKQWpnRUV3RUNBQ0lGQWx0NmdCTUNHd01HQ3drSUJ3
 TUNCaFVJCkFna0tDd1FXQWdNQkFoNEJBaGVBQUFvSkVKU0I3QThSa1BMYmpic1AvamdqYVNz
 NUh0bGtBSXZXUytGcm15N2MKaG5jT0F4TFRWL0Q2UkV3SU95R0poRkt3d29pck55UTJnOXZV
 YTNZQ1lDZjFmSjh3RWhhS09COWQwTHBNUm5MNApkRVQ4ZDgyMzhFL3BLK0hxTktpSXNKaHM2
 SnNLOFpnalZRR3JtbWZua0dyWisxdjBIQnV4ZGljZ0duUC9XdHVBClVsOGw2Mi9BTGJheXlq
 KzYxQ2xyc0V0UklhcU82N0xJWXdQaVBEUkkrWGlNek5pR3pIRi8xUTZHUjAyUkg2YTMKRjg5
 ejhhUHhjSGkxWnZDdDJ5a3o2VUVjaHpQMHI1Z3FGSisvTC9VcHU4ME1YaVk0djVlSWFCNTJn
 VlBnaXlNQQpsTDJkRHMxbUladm5yUkxSWTJ0YjNtQVlOa1Y1QjVJRFQzcGtXeTZrS281T0Nn
 SytZZFlPUjhGTloyb04ydDhPCnJLK1ZudGFLN01NU0tIbG1ZL3NPd3RSbEVoMU9CbXJjQ3dH
 d21wLzA1R2tSNDZmL0lzaFJWZUZPUmF3K0dBcXQKUDIrQ0ZhMkNOQS9JSG5aTm95aWtsRHpQ
 UUhVVUdzck5wcERyaFg5Sm1oQm1nMXYyeXdIMU5YdTFpRGZQMUJBdwpLZ29rdDVmNVVhUkY5
 c0FBNTN2V0V2YlVVTjllZXNGR0x6UFdkSkdRNWhwZC9WSDVJUXk5U0JyaC93SWNla3E1Cm4w
 a042cGJUSHhHRTUyU2kvTVZJa05UdURaM2FwbjJqbERaNHBPdHBCWEkydlAzYlBPK05pcUJa
 anNVM3R4TGkKV2R2MkZqeXp6NlhMUndlV1JZVkw1SGE2TER0eG9yMnZ1NlVQMDdwOXh6MXhS
 WmFPRFczb1lsSEZ6WXBhNFc1ZwpMSGIybEVrSXVVZlNjaWNHYmpqQXRDbFRkR1ZtWVc0Z1Yy
 Rm9jbVZ1SUR4emRHVm1ZVzR1ZDJGb2NtVnVRR2x1CkxYUmxZMmd1WTI5dFBva0NOd1FUQVFn
 QUlRVUNYSWRlaHdJYkF3VUxDUWdIQWdZVkNBa0tDd0lFRmdJREFRSWUKQVFJWGdBQUtDUkNV
 Z2V3UEVaRHkyeUhURC85VUY3UWxEa0d4elE3QWFDSTZOOTVpUWY4LzFvU1VhRE51Mlk2SQpL
 K0R6UXBiMVRiVE9yM1ZKd3dZOGEzT1d6NU5MU09MTVdlVnh0K29zTW1sUUlHdWJEM09EWko4
 aXpQbEcvSnJOCnQ1elNkbU41SUE1ZjNlc1dXUVZLdmdoWkFnVERxZHB2K1pIVzJFbXhuQUox
 dUxGWFhlUWQzVVpjQzVyMy9nL3YKU2FNbzl4ZWszSjVtTnVEbTcxbEVXc0FzL0JBY0ZjK3lu
 TGh4d0JXQld3c3Z3UjhiSHRKNURPTVd2YUt1RHNrcApJR0ZVZS9LYjJCK2pyYXZRM1RuNnMv
 SHFKTTBjZXhTSHo1cGUrMHNHdlArdDlKNzIzNEJGUXdlRkV4cmlleThVCkl4T3I0WEFiYWFi
 U3J5WW5VL3pWSDlVMWkyQUlRWk1XSkFldkN2VmdRL1UrTmVSaFh1ZGU5WVVtRE1EbzJzQjIK
 VkFGRUFxaUYyUVVIUEEybThhN0VPM3lmTDRyTWswaUh6TElLdmg2L3JIOFFDWThpM1h4VE5M
 OWlDTHpCV3UvTgpPbkNBYlMremx2TFphaVNNaDVFZnV4VHR2NFBsVmRFamY2MlArWkhJRDE2
 Z1VEd0VtYXpMQU1yeDY2NmpINWt1ClVDVFZ5bWJMMFR2Qis2TDZBUmw4QU55TTRBRG1rV2tw
 eU0yMmtDdUlTWUFFZlFSM3VXWFo5WWd4YVBNcWJWK3cKQnJoSmc0SGFONkM2eFRxR3YzcjRC
 MmFxYjc3L0NWb1JKMVo5Y3BIQ3dpT3pJYUFtdnl6UFU2TXhDRFhaOEZnWQpsVDR2MjNHNWlt
 SlAyemdYNXMrRjZBQ1VKOVVRUEQwdVRmK0o5RGEycitza2gvc1dPbloreWNvSE5CUXZvY1pF
 Ck5BSFFmN2tDRFFSYmVvQVRBUkFBMkhkMGZzRFZLNzJSTFNESGJ5ME9oZ0RjRGxWQk0yTSto
 WVlwTzNmWDFyKysKc2hpcVBLQ0hWQXNRNWJ4ZTdIbUppbUhhNEtLWXMya3YvbWx0L0NhdUNK
 Ly9wbWN5Y0JNN0d2d25Lem11WHp1QQpHbVZUWkM2V1I1TGtha0ZydEhPelZtc0VHcE52NVJj
 OWw2SFlGcExrYlNrVmk1U1BRWkp5K0VNZ01DRmdqclpmClZGNnlvdHdFMWFmN0hOdE1oTlBh
 TEROMW9VS0Y1aitSeVJnNWl3SnVDRGtuSGp3QlFWNHBndzIvNXZTOEE3WlEKdjJNYlcvVExF
 eXBLWGlmNzhJaGdBelh0RTJYck0xbi9vNlpINzFvUkZGS096NDJsRmR6ZHJTWDBZc3FYZ0hD
 WAo1Z0l0TGZxemoxcHNNYTlvMWVpTlRFbTFkVlFyVHFueXMwbDE4b2FsUk5zd1lsUW1uWUJ3
 cHdDa2FUSExNSHdLCmZHQmJvNWRMUEVzaHRWb3dJNm5zZ3FMVHlRSG1xSFlxVVpZSXBpZ21t
 QzNTd0JXWTFWNmZmVUVta3FwQUFDRW4KTDQvZ1Vnbjd5US81ZDBzZXFuQXEycFNCSE1VVW9D
 Y1R6RVFVV1ZraUR2M1JrN2hURm1oVHNNcTc4eHYyWFJzWApNUjZ5UWhTVFBGWkNZRFVFeEVs
 RXNTbzlGV0hXcjZ6SHlZY2M4cURMRnZHOUZQaG1RdVQyczlCbHg2Z0kzMjNHCm5FcTFsd1dQ
 SlZ6UDRqUWtKS0lBWHdGcHYrVzhDV0xxekRXT3ZkbHJEYVRhVk1zY0ZUZUg1VzZVcHJsNjVq
 cUYKUUdNcGNSR0NzOEdDVVcxM0gwSXlPdFF0d1dYQTRueStTTDgxcHZpQW1hU1hVOGxhS2FS
 dTkxVk9WYUY5ZjRzQQpFUUVBQVlrQ0h3UVlBUUlBQ1FVQ1czcUFFd0liREFBS0NSQ1VnZXdQ
 RVpEeTIrb1hELzljSEhSa0JaT2ZrbVNxCjE0U3Z4MDYyUHRVMEtWNDcwVFNucC9qV29ZSm5L
 SXczRzBtWElSZ3J0SDJkUHdwSWdWanNZeVJTVk1LbVNwdDUKWnJEZjlOdFRiTldnazhWb0xl
 WnpZRW8rSjNvUHFGclRNczNhWVl2N2U0K0pLNjk1WW5tUSttT0Q5bmlhOTE1dApyNUFaajk1
 VWZTVGx5VW15aWMxZDhvdnNmMWZQN1hDVVZSRmNSamZOZkRGMW9ML3BEZ01QNUdaMk93YVRl
 am15CkN1SGpNOElSMUNpYXZCcFlEbUJuVFlrN1B0aHk2YXRXdllsMGZ5L0NxYWpUS3N4Nytw
 OXh6aXU4WmZWWCtpS0IKQ2MrSGUrRURFZEdJRGh2TlovSVFIZk9CMlBVWFdHUytzOUZOVHhy
 L0E2bkxHWG5BOVk2dzkzaVBkWUl3eFM3SwpYTG9LSmVlMTBEamx6c1lzUmZsRk9XMFpPaVNp
 aElDWGlRVjF1cU02dHpGRzlndFJjaXVzNVVBdGhXYU8xT3dVClNDUW1mQ09tNGZ2TUlKSUE5
 cnh0b1M2T3FSUWNpRjNjcm1vMHJKQ3ROMmF3WmZnaThYRWlmN2Q2aGp2MEVLTTkKWFpvaUFa
 WVpEKy9pTG01VGFLV042b0dJdGkwVmpKdjhaWk9aT2ZDYjZ2cUZJa0pXK2FPdTRvclRMRk16
 MjhhbwpVM1F5V3BOQzhGRm1kWXNWdWE4czZnTjFOSWE2eTNxYS9aQjhiQS9pa3k1OUFFejRp
 RElScmdVek1FZzhBazdUCmZtMUtpWWVpVHRCRENvMjVCdlhqYnFzeXhrUUQxbmtSbTZGQVZ6
 RXVPUEllOEp1cVcyeEQ5aXhHWXZqVTVoa1IKZ0pwM2dQNWIrY25HM0xQcXF1UTJFNmdvS1VN
 TEFia0NEUVJiZmw5REFSQUFzRExjYStMbFAydm5mdEVHaHBjQQpCR1ZOUUVGbkdQckNhdVU2
 SGhOODA1V3RQVHRtc1JPdUp6cWdVVDBtcHFXSWZacTZzTXd5dkhLOVRzL0tIM0paClVWYlJD
 M3oyaDNLZmhIL0RhZjk1cGQ2bVBjL2g5dkYvT3kzK2VUV2hnR25QNmNBNWtsUitmTzFXaEc4
 VnJpWHYKck5lUkcyMHN6emplSG9jblNJY1Q1WHVaUjB1REhPaUd4T2l6MXNNUkZUR3h6R095
 MTlSOXJ2dTYzdGlJM2Q3dgpnYzc1T0NBZGtlQi9TZUNFbGFSdzBUZjdMWmJQampzRjI2M0JZ
 bk1mNGtrTkVLdnFXY1UyaWNNcCtxZXpqeW5CCnB2ZXVlMHJDVFFCWUFRbG9GQ1ZUR0hyV1dB
 NkQ0VzVPMkFmSWRJYzF1MUpDWnAyZjVMV1ZvVUZUVklyUW5RUVUKU0hDaWZyOU1aeExUdFBK
 ZFU1Mm9TUHczZGs0aExQOGlKSUx1dnYvYXZhakNzUVlIRXR3WXNiZUZaeGl1TGdscApBN1lj
 Sk5ObXBnQ3BNRDR3VWh2bEN0QUtOQlFXeXIyOTc2OThFUVRuNDZlQmVVNkttMkNpaFhrZ3dD
 eWY4ZXlLCkxFM3NYZXdhcTVrZ1pXdk5xNml1NXFZSVJCOXl3K2NYYzYwZE9aRE9scTkzWDVT
 QVJZemFvZXBrSHo0cmtMa1AKUG8rdENIeUhRUHNHblBYYzlXVDgwREM5Tm5KR2R2VWx5NXJk
 TUk0eHBaeWdlb2tqd293VlFsUFV1Y1M2TXluNwpmOHc4Y2dmQjdDMklBSWNEeDJwUC9IendY
 dmtDT1FOQTdtVjFsTTA4bitnVmtUcnpweGlwNURicTRDSW9ZeDJNCkpaVDhiR1JINlhqY1VE
 S2EwOVFoeVpzQUVRRUFBWWtFUkFRWUFRZ0FEd1VDVzM1ZlF3SWJBZ1VKQThKbkFBSXAKQ1JD
 VWdld1BFWkR5MjhGZElBUVpBUWdBQmdVQ1czNWZRd0FLQ1JCVnhETFBjVk1NamNkc0QvMFJo
 QXN1UVlPeQpyMTNCbDNOaFhrWUFaR3AyWkZER3VrZTdPU2tWOG9qT09UZFR5ei9jT1JHQ2J5
 ZEQrRGd2cUZ5VmRuT1hLZ08wCmxKbUd3ckdlTGRnZ0F2aDBpaHJwNU8wWVVKOWJCU1htR01t
 UVRZSC9BbUxUR2FkYnVqQ1dqNWZGVWtDeXd4aW0KSHV5MFBiMjRwelR2UzUwR1k1WStxSDBG
 SE5haWdka2tpV04zcnVnN0haRXUvQ3lsUFpqT1h6K0QxUVBNckV4dwo3ZC9NS2FiVis5YU5i
 UVlabGRJajk4UXd2VUYxS1N6YThqbFVJdnBoUnEyN0FUOGZER1lHUGZERU1nMmNCT2FlCkty
 N29uUXM0YjdhV082aWZEbHhRVHB6c3pvK0FuODA3Tk1TdFZFRmYrczNBaFZEM2U3bmY4SkJh
 dmJWckFlMGsKb20yNm96elBubnh6K2xxVlZ0dzZVazRYTUl6dGl4L0h3SFl3dUNuY1VYWndL
 MEkzeUFKd2pZd29vck9DaEozUwpFVWJKUVB0R3NneFJERXhWQkZlNk5MUC82MnhQOU82dGFj
 d09kYjBNbVAxYjM5cFJBVEM3YmdkMWxkVUxpNzVaCmxKckowL1NpVkVyb3FOWXk3OXRmbWdB
 WjJVeFptczlTckV5Nm85UVNmc24xYVh2K01QTDlKYUNHbWtQNnpiTFEKTm5kajBKY2FRbmtD
 MHZneWRPMUJtNk11OTZQOXVmbEtaY0FTNndtTE01SWRIT3lqTDg4d0h3anVjakFPQnRjdwpw
 MG9HVG5WT25Sc05ZU084VzhZWi9LZGJ1Nzg1ZGF6TXFKMmlOakFEdUJiZG02TjRqNUVkTW5r
 TG4wQklmUEpwCmRnbTR2bDJVcExqd1JHci9NM3dtbTVwdnMrNnVCN2hrL0ZKaUQvNGxsRU5Q
 NGVNMWg3U200aitWcTZOMSt6VEIKSVhKQWViSXFhc0RwNXlaUzdYcnk0STM2bjg1WEVZZkcw
 MWx0QXlob05WMkRPOFNJUlFwdWkydHErOVJQM1JLMQpKREJ4eEVKWTJFTzVKWjhNeGFQSFEw
 RFQwNWxSRmpLMkFsaGRFSXRqTGpwSjNmVW05c3FMeE1XeHpQNlV6M2lpCjJ1YTR1bnJ0Nk9D
 VHFRd2lqRi8zYlRXaXd2VkFBSG5NRlVpb1hzaEhhb2hWRGNWZm5lSU1mVjBiUUNYWWkzTnAK
 WTB2MFp3Y2lGSCtnU0M3cUQ2WE51aHBWR1NMNElpbGlGeS9TemNhSkV6QUhlTERTaFpQMkNX
 ZG5DNHZnbDM3dApocHg4aDU1WWhKbjZIU3VVelBnaGFLdFZCMmsrajdaZXlaK1NGeHA3SXVi
 SEN3TEhsUWhUNzVSd1EzaUF4S242CjBxajUxY1lUbnF4ZFpYVzZmSDNQa3VNellVNUdwcVIv
 MU9sNWMvd2ZJNmc2QW04eUtXLzBFVUx0K0tuNExGc1MKbTdZM201SDV2MTJVNkpCWXZWK3Ix
 M2paaW9zNEVFREU5M0Q1c05IMk1JeVJ6Q0RxMXpkZHQ0WHV5S0ZqUEtXMQo5aWJaRGZGVjdL
 dUNzdnVMMjNzQmMxc0NNb3ArRTFtVC9ReE9JQTZvRFQxTVFzdHdPVnVReURDdi9PdktTZ2Z6
 CjhGWEdMNkFQY2xqQ3FqOEFKaHhReXN4ZG9pUVA4bS92dStialdHR3Z4dzVzMWxncGlSRFRS
 VVBnY0pKTmFHWTIKVklEclpRaTROU2lOUTBOSWkrZGp1NGZOTW1DcFFxZzh0YkMzY0FhNnl3
 bTZvUUIxU0JobURYMmUxMWdSbGx1SQpPblRHUEUwSFRvM2w3MmxoYmc9PQo9cVpNVgotLS0t
 LUVORCBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCg==
Message-ID: <27a549fe-e38d-f9a2-2677-ae5b5dc1aa45@i2se.com>
Date:   Tue, 1 Sep 2020 18:31:07 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20200901095829.64a5hjghf3mlsyvo@gilmour.lan>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 8BIT
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Maxime,

Am 01.09.20 um 11:58 schrieb Maxime Ripard:
> Hi Stefan
>
> On Tue, Aug 25, 2020 at 11:30:58PM +0200, Stefan Wahren wrote:
>> Am 25.08.20 um 17:06 schrieb Maxime Ripard:
>>> Hi Stefan,
>>>
>>> On Wed, Jul 29, 2020 at 05:50:31PM +0200, Stefan Wahren wrote:
>>>> Am 29.07.20 um 16:42 schrieb Maxime Ripard:
>>>>> Hi,
>>>>>
>>>>> On Wed, Jul 29, 2020 at 03:09:21PM +0100, Dave Stevenson wrote:
>>>>>> On Wed, 8 Jul 2020 at 18:43, Maxime Ripard <maxime@cerno.tech> wrote:
>>>>>>> In order to avoid pixels getting stuck in the (unflushable) FIFO between
>>>>>>> the HVS and the PV, we need to add some delay after disabling the PV output
>>>>>>> and before disabling the HDMI controller. 20ms seems to be good enough so
>>>>>>> let's use that.
>>>>>>>
>>>>>>> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
>>>>>>> ---
>>>>>>>  drivers/gpu/drm/vc4/vc4_crtc.c | 2 ++
>>>>>>>  1 file changed, 2 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
>>>>>>> index d0b326e1df0a..7b178d67187f 100644
>>>>>>> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
>>>>>>> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
>>>>>>> @@ -403,6 +403,8 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>>>>>>>         ret = wait_for(!(CRTC_READ(PV_V_CONTROL) & PV_VCONTROL_VIDEN), 1);
>>>>>>>         WARN_ONCE(ret, "Timeout waiting for !PV_VCONTROL_VIDEN\n");
>>>>>>>
>>>>>>> +       mdelay(20);
>>>>>> mdelay for 20ms seems a touch unfriendly as it's a busy wait. Can we
>>>>>> not msleep instead?
>>>>> Since the timing was fairly critical, sleeping didn't seem like a good
>>>>> solution since there's definitely some chance you overshoot and end up
>>>>> with a higher time than the one you targeted.
>>>> usleep_range(min, max) isn't a solution?
>>> My understanding of usleep_range was that you can still overshoot, even
>>> though it's backed by an HR timer so the resolution is not a jiffy. Are
>>> we certain that we're going to be in that range?
>> you are right there is no guarantee about the upper wake up time.
>>
>> And it's not worth the effort to poll the FIFO state until its empty
>> (using 20 ms as timeout)?
> I know this isn't really a great argument there, but getting this to
> work has been quite painful, and the timing is very sensitive. If we
> fail to wait for enough time, there's going to be a pixel shift that we
> can't get rid of unless we reboot, which is pretty bad (and would fail
> any CI test that checks for the output integrity).
>
> I know busy-looping for 20ms isn't ideal, but it's not really in a
> hot-path (it's only done when changing a mode), with the sync time of
> the display likely to be much more than that, and if it can avoid having
> to look into it ever again or avoid random failures, I'd say it's worth
> it.

i don't want to delay this series.

Could you please add a small comment to the delay to clarify the timing
is very sensitive?

Thanks

>
> Maxime