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bh=mKkSHxlGKWwLAVWzC2ngK+QD6aN8k+ksqhaW6x0BrfQ=; b=A9surNlwNl1Sh8hothZthwuoJ54i2YTw7bQLtr8+Bn2tspofyF/qkhK7uqKMIdV58CI4YW L3CJt5cceI3qZa6lPgOGcIJgqLBaTKTz/wMVv8n2ajk5j3knnabov2GzGWKZ3mJ1OHs6Df XIMZocbJFiJu+GW/cy6AFBEc0nmpxTcN+rT9Z4tHDaw1sAttHD29ZYzyGtU+iK9qCMFqAG 95ohkEw3+zhdwt2Eiu41rsBqlGhvc5tgSHOMDTlXcXF3uFKGXV7O0m0T5iyQQ6BZHcprwP jNdRXL+pab7xYClw6jJU1NJx5kblCxghvSzsL9aEkXYWfEGjf1Z4Qpz8b6KnLA== Date: Mon, 14 Apr 2025 23:58:07 +0200 From: Alexandre Belloni To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Alexandre Mergnat , AngeloGioacchino Del Regno , Eddie Huang , Sean Wang , Matthias Brugger , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v3 4/5] rtc: mt6397: Remove start time parameters Message-ID: <20250414215807b1b6b008@mail.local> References: <20250109-enable-rtc-v3-0-f003e8144419@baylibre.com> <20250109-enable-rtc-v3-4-f003e8144419@baylibre.com> <20250411133609a1295543@mail.local> <202504111339359e840246@mail.local> <968001f7-96d1-4ad5-8c36-28cac5dc30f1@collabora.com> <97cfeafe-7044-4f06-b2e6-e4a158419473@baylibre.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddvvdduieelucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvvefukfhfgggtugfgjgesthekredttddtudenucfhrhhomheptehlvgigrghnughrvgcuuegvlhhlohhnihcuoegrlhgvgigrnhgurhgvrdgsvghllhhonhhisegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpeevudevhfdvheelgfeileefteduuefghefguefgkeeljeeufeeutedtffeuteeivdenucffohhmrghinhepsghoohhtlhhinhdrtghomhenucfkphepvdgrtddumegvtdgrmedvugemieefjedtmeejkegvtdemtgdtvgekmedvkedtieemkegrtgeinecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddumegvtdgrmedvugemieefjedtmeejkegvtdemtgdtvgekmedvkedtieemkegrtgeipdhhvghloheplhhotggrlhhhohhsthdpmhgrihhlfhhrohhmpegrlhgvgigrnhgurhgvrdgsvghllhhonhhisegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopedugedprhgtphhtthhopehurdhklhgvihhnvgdqkhhovghnihhgsegsrgihlhhisghrvgdrtghomhdprhgtphhtthhopegrmhgvrhhgnhgrthessggrhihlihgsrhgvrdgtohhmpdhrtghpthhto heprghnghgvlhhoghhiohgrtggthhhinhhordguvghlrhgvghhnohestgholhhlrggsohhrrgdrtghomhdprhgtphhtthhopegvugguihgvrdhhuhgrnhhgsehmvgguihgrthgvkhdrtghomhdprhgtphhtthhopehsvggrnhdrfigrnhhgsehmvgguihgrthgvkhdrtghomhdprhgtphhtthhopehmrghtthhhihgrshdrsghgghesghhmrghilhdrtghomhdprhgtphhtthhopehrohgshheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepkhhriihkodgutheskhgvrhhnvghlrdhorhhg X-GND-Sasl: alexandre.belloni@bootlin.com On 14/04/2025 23:34:48+0200, Uwe Kleine-König wrote: > > > Yes, you're stuck with this. Devicetree has to be retrocompatible. > > > > > > Besides, this start_secs is what gets used by default, and the start-year > > > devicetree property should take precedence and effectively override the > > > start_secs default. > > > > > > Just keep it there.... :-) > > It would work to keep setting start_secs but allow overwriting that > value in the device tree. But see below. > This is already the case. > > When you boot your board for the first time, is the date January 2nd 1968 ? > > If not, that mean it is used as a finetune offset year. > > IMHO, mktime64(1968, 1, 2, 0, 0, 0) is a workaround for the rtc framework > > issue we try to solve in this serie because start_secs is negative (1968 < > > 1970). Now framework handle the negative value properly, even if you keep > > mktime64(1968, 1, 2, 0, 0, 0) , the device time will change. I prefer to > > notify you. :) > > I don't understand everything you wrote here, but as far as I see it, > rtc_time64_to_tm() not being able to handle dates before 1970 is the > main issue here. This is of course only relevant, because your hardware > occasionally contains such a date. The technically right fix is to > extend rtc_time64_to_tm() to work for dates >= 1900-01-01. (An > alternative would be to assume that a hardware read returning a date > before 1970 is invalid. If you refuse to write dates before 1970 that > should give a consistent behaviour. But the original approach is the > nicer one.) > Yes, the assumption is that dates before 1970 are definitively invalid. I still believe we live in a world were the time doesn't go back ;) Android *was* the only OS requiring to be able to set 01/01/1970. This changed after they realized that some hardware is not able to do that. > > TBH, it's hard to follow the logic, so I've a question: > > If I push in my V4 a framework fix that drivers using year < 1970 will need > > to have a new start_secs or start-year value to stay aligned with there > > previous value, do you will accept it ? > > Doesn't the need to shift the start year simply goes away once > rtc_time64_to_tm() is fixed for negative time values? > > So I would expect that going forward with just patches #1 and #2 should > result in a fixed driver regarding the breakage you're seeing. (I'm > unsure about patch #3, I'll address that in a reply to the respective > mail.) > This is also what I think but I don't think I'm going to allow the rtc_valid_tm() change. It shouldn't matter as the check should always happen after offsetting/windowing. -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com