From patchwork Wed Jul 10 13:29:14 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Andr=C3=A9_Draszik?= X-Patchwork-Id: 13729325 Received: from mail-ed1-f50.google.com (mail-ed1-f50.google.com [209.85.208.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A5C06192B71 for ; Wed, 10 Jul 2024 13:29:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.50 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720618159; cv=none; b=DF1euIiI0ADauOKMsXOKyVgqn+KriM98kReWYI1AGMQORKudWExOA+4pwubGcEzpMxXb1PaMacrLHcPGiMZ1BbQ8sx+hY4jm1Jzjc3pTQpF/uhTokpUyh6q7UWTAON0xDhh8UH1GaFTpkKWAOEj3BRLx9/YbFzGE/AI22k9E0Gw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720618159; c=relaxed/simple; bh=AKISzd5iyKCiNSgNN74C2eS4DaC2iGHXlNn55yMvsmk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TBdhWUUREJPOJlbuzldFU0/fK5n/iCzEVRWqyQlhYtP0tFSQRWKH14dSZlq4ui+WqCWZ2kbSiJNYKmIsktT+ftif9qaFZLTkOXllFXlofDU+G6EhspRi1JI6BYQniVrfbwN2iJx7AX6PIZqyFF5WzEWwXCRhbgUt63WFo4N+3aw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=nkf3JSeH; arc=none smtp.client-ip=209.85.208.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="nkf3JSeH" Received: by mail-ed1-f50.google.com with SMTP id 4fb4d7f45d1cf-595712c49ebso2336023a12.0 for ; Wed, 10 Jul 2024 06:29:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1720618156; x=1721222956; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=sXpfd2wmtmBO96JF5yDlmVCc6EbK2CgZGn/Nuo/rMog=; b=nkf3JSeH1I1DFNFUTre5FkhoyHn9SKxwZE3oKyo0JM60ZJ7/YHLH1E5osfOmgB/LEC TB4DwIk63lTcnaFa/52dIU0mi/R8FpLyKNaD1vpYwVdrXOA7zHHH9qji+Phxoes3eRct N+xARu4+dS4LzV9VwEzrHcp5OEZInxpDaKM57cYhUS/cgZh7SRjh30gII4BOqMiCgqJq W/MOa+SGO5kWxLGQKvnOo9WIW2cgqLWex1j4UTUPWXeQAVwbNdMErXVGZGUnUnyxEXSW 0fJlTM8i4S9z1tKCpue9Psh4T3xzIpGZM1hB3vv8llcMn0cA0lAJlSN8IA0GAM7b7FDw EyPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720618156; x=1721222956; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=sXpfd2wmtmBO96JF5yDlmVCc6EbK2CgZGn/Nuo/rMog=; b=vS9z60RskDvnw/VBThhXF9gC+705bv2OyGqSx6efLnxKxFidsWY3eRySFYZbZDRL8Y A+a+qx0AlQji16XDMIfGo4W5nQ/G0d21kjkHDpxlG4mhaa0uC8a/cOm+gWI9Fs1Yd3dy VfrgYLgolytR9fOCRT74ppQR3h8hXx+BvxHuiT7EfssL/MPvUfvboPr2ZZ4Z5BmazF2r IVmHhaV5K5VPKWTn90692EGV/Rfz+kMgnZ0s/Q4MpGtSUZNMCqfz6S9edjLYGM4i1sSI tHmpPPP3tLo4a7n8qlc39HYpevBfDBHWS9qW9CXIKEEweqSkxy+CTwsc+qKvGwQDe+jc dRBw== X-Forwarded-Encrypted: i=1; AJvYcCWZbMpgilIcglbK76/tkYndx66/9D8evxa7U8ec7Fcw1drEwbTkcu9z0UCKQ7HdpI+y+S8+JBYmeAlY/Kk2spjpuIH9h1nkW/6i X-Gm-Message-State: AOJu0YyuvM/N1gRLs10Qb3bRdQaonyIBu6vd7jOerNeBQyZsa96otp57 ixOW+3Ibbeu7F11mJrPP5B2mVUpcOcp5fA4KwlJrlh0/vF3smXL46jv8CX9w4UM= X-Google-Smtp-Source: AGHT+IFdiZRQ6U4xwH4ESlWOcT7tTqHneAgzJZJftzH/4QoiYntL7Tm+hCt6+4O1lTffIWQm0nWIMw== X-Received: by 2002:a05:6402:34c8:b0:595:7c14:18da with SMTP id 4fb4d7f45d1cf-5957c141933mr3328492a12.34.1720618155985; Wed, 10 Jul 2024 06:29:15 -0700 (PDT) Received: from puffmais.c.googlers.com (8.239.204.35.bc.googleusercontent.com. [35.204.239.8]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-594bd45a162sm2204844a12.68.2024.07.10.06.29.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jul 2024 06:29:15 -0700 (PDT) From: =?utf-8?q?Andr=C3=A9_Draszik?= Date: Wed, 10 Jul 2024 14:29:14 +0100 Subject: [PATCH v3 1/2] dt-bindings: serial: samsung: fix maxItems for gs101 & document earlycon requirements Precedence: bulk X-Mailing-List: linux-clk@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240710-gs101-non-essential-clocks-2-v3-1-5dcb8d040d1c@linaro.org> References: <20240710-gs101-non-essential-clocks-2-v3-0-5dcb8d040d1c@linaro.org> In-Reply-To: <20240710-gs101-non-essential-clocks-2-v3-0-5dcb8d040d1c@linaro.org> To: Greg Kroah-Hartman , Jiri Slaby , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Peter Griffin , Sylwester Nawrocki , Chanwoo Choi , Alim Akhtar , Michael Turquette , Stephen Boyd , Sam Protsenko , Tudor Ambarus Cc: Will McVicker , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-clk@vger.kernel.org, =?utf-8?q?An?= =?utf-8?q?dr=C3=A9_Draszik?= X-Mailer: b4 0.13.0 While gs101 needs exactly two clocks for the UART, the schema doesn't currently limit the maximum number to this and instead the default of five from this schema is applied. Update the schema accordingly. Also, as pointed out in [1] before, the hand-over between earlycon and serial console is fragile due to clocking issues, at least on Google Tensor gs101. Therefore, document the clocking requirements for earlycon in the description for posterity, so the information is not lost. Link: https://lore.kernel.org/all/d45de3b2bb6b48653842cf1f74e58889ed6783ae.camel@linaro.org/ [1] Signed-off-by: André Draszik --- Documentation/devicetree/bindings/serial/samsung_uart.yaml | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/devicetree/bindings/serial/samsung_uart.yaml b/Documentation/devicetree/bindings/serial/samsung_uart.yaml index 0f0131026911..2435c3d92158 100644 --- a/Documentation/devicetree/bindings/serial/samsung_uart.yaml +++ b/Documentation/devicetree/bindings/serial/samsung_uart.yaml @@ -145,6 +145,20 @@ allOf: - samsung,uart-fifosize properties: reg-io-width: false + clocks: + description: | + Note that for earlycon to work, the respective ipclk and pclk need + to be running! The bootloader normally leaves them enabled, but the + serial driver will start handling those clocks before the console + driver takes over from earlycon, breaking earlycon. If earlycon is + required, please revert the patch "clk: samsung: gs101: don't mark + non-essential (UART) clocks critical" locally first to mark them + CLK_IS_CRITICAL and avoid this problem. + maxItems: 2 + clock-names: + items: + - const: uart + - const: clk_uart_baud0 unevaluatedProperties: false