From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f53.google.com (mail-ed1-f53.google.com [209.85.208.53]) (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 6AD8C76C88 for ; Mon, 29 Jan 2024 17:46:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706550408; cv=none; b=KfyA1xHpIdwWKjIGQbVQ/rEczjQ1mNMmy/UQ1zzGI0m9U9EYTNERl5QqGhdtoq0CoFZEdIXHdOHR62xivogkSK240SuFJtkDtnMPjjxKDYEwzLMYkS9T0HnImt1So8HwpcsTRX0zAAwRhpF8I52AGBugQRlya60dm43I4c3UO7I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706550408; c=relaxed/simple; bh=vV6AH3YtSu3SS+W/E8VEkUhNHcf73by0FdjpTGcjHC0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Uxb78FCdtmVJI1MbsChNL2BEqExTIMO2AQxAtMuXoGRxcS8uuBRSfKHN+4Cag64NWtm9lOM1XLid9oyNTilc+TLD8HOYSJ6r3acluFR2GG/R1ldHqlJwSg0H0HLQKexPZasisyjRInyIExGZrM+9TvQRUFoVv1XtOVXzCp7DCtg= 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=uDgcUv75; arc=none smtp.client-ip=209.85.208.53 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="uDgcUv75" Received: by mail-ed1-f53.google.com with SMTP id 4fb4d7f45d1cf-558f523c072so3358990a12.2 for ; Mon, 29 Jan 2024 09:46:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1706550403; x=1707155203; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=vV6AH3YtSu3SS+W/E8VEkUhNHcf73by0FdjpTGcjHC0=; b=uDgcUv75M7IlthBEvGXeD4bYEoSDba0GC1J8cmYS15XY20I5r7duN3DNNWh5SAyYFn 2OyPwBd5oRnn3MURHsBxxF2tmWFOYRlp9C2WEiN6q/SRgQf/QjMMn1Yb12EohDRhj0rA 5ZVDeCCjxCm2Ok9flDPCl6HfeOLcG7G7KRXgidXZIg5NnXU63v4yUO/5ZdQGSIFIEuWq 5AetPQfv0qQxfUPa4AGKYEuiPAxGxK0fchL6E6r+CT3lUIpz/Fe01QlFUtN37x+UINMx V3kQctrg6hfebScD5ALSQ8XAKDpshiZ9LW/O/chiKaohcbTjz+7zCQHQQXBRRhBdqGRW gy8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706550404; x=1707155204; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=vV6AH3YtSu3SS+W/E8VEkUhNHcf73by0FdjpTGcjHC0=; b=rDgqj/tAk6jLBxz0yX+SJtcgqAto03urtMDf9/CuKlY9dbykBPFG4LMIjXfVVEbmcr ylblNK40EwEisjWuncO5gImr+4DpfID15vZMquWKdsoozdwMLZjszQ2zYUeCtdCVqBLl RJFkPPq3XrayDeU2LIO8sZV+zTgPec5Hwa/EhC3PuAf8hYeGeQN+B3stCpXqYwf02aKc 2bxALTWbvjZTmpMjiUwJRMs1Ay+Ba61w8vwHWyd3B+z8ORxQizfWbn7a6S05suyl97kP Fr7Wc7fcNXpKHIjrUXVRC80uTdE7mJv2wv/nrv62SH57UFfNnu13Vto/L2MzzEzyUIpT ZUJA== X-Gm-Message-State: AOJu0YwqyFrYeL+Qw9voYmY9d8v5uYeOT7ykMuy87+BVOB1yNtOMplhf nb+lkDgKw3hfpxka8+zmA2Rl1JkkmB6PucVWgz5UlOFtRCapy526xfRpyCXsGZE= X-Google-Smtp-Source: AGHT+IFqKB6Afd8ptGOeQ1QAT1e1DmbB0LTR7hNkH3waGYNb+bZ3bz0noe/Y9mqDg1A1YIeGo4RQmg== X-Received: by 2002:a17:906:33d2:b0:a2d:bc90:de6b with SMTP id w18-20020a17090633d200b00a2dbc90de6bmr4726997eja.30.1706550403711; Mon, 29 Jan 2024 09:46:43 -0800 (PST) Received: from [192.168.2.107] ([79.115.63.202]) by smtp.gmail.com with ESMTPSA id vo2-20020a170907a80200b00a352c0bb7basm3288323ejc.81.2024.01.29.09.46.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jan 2024 09:46:43 -0800 (PST) Message-ID: <99b7501d-6780-4227-8558-488b1b9da758@linaro.org> Date: Mon, 29 Jan 2024 17:46:41 +0000 Precedence: bulk X-Mailing-List: linux-clk@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] clk: samsung: exynos850: Propagate SPI IPCLK rate change Content-Language: en-US To: Sam Protsenko , Krzysztof Kozlowski , Rob Herring , Conor Dooley Cc: Alim Akhtar , Sylwester Nawrocki , Tomasz Figa , Chanwoo Choi , linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20240125013858.3986-1-semen.protsenko@linaro.org> <20240125013858.3986-2-semen.protsenko@linaro.org> From: Tudor Ambarus In-Reply-To: <20240125013858.3986-2-semen.protsenko@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, Sam, On 1/25/24 01:38, Sam Protsenko wrote: > Which should cover all possible applications of SPI bus. Of course, > setting SPI frequency to values as low as 500 kHz will also affect the > common bus dividers (dout_apm_bus or dout_peri_ip), which in turn > effectively lowers the rates for all leaf bus clocks derived from those > dividers, like HSI2C and I3C clocks. But at least it gives the board > designer a choice, whether to keep all clocks (SPI/HSI2C/I3C) at high > frequencies, or make all those clocks have lower frequencies. Not > propagating the rate change to those common dividers would limit this > choice to "only high frequencies are allowed for SPI/HSI2C/I3C" option, > making the common dividers useless. This decision follows the "Worse is > better" approach, relying on the users/engineers to know the system > internals when working with such low-level features, instead of trying > to account for all possible use-cases. Depending on clock frequencies in DT and on the order of probe, one may end up with SPI changing the frequency for I3C for example, there's no protection on that. The more conservative approach, to which I lean, is to propagate the clock just to the first divider, which is dedicated to the end note, thus you'll avoid such problems. I think this fine tuning that you allow is more suitable for downstream. Maybe this is more of a personal preference, I don't know. Curious what others think. The patch is looking fine though, and if the approach is considered acceptable: Reviewed-by: Tudor Ambarus