Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) client-ip=2620:137:e000::3:5;
Message-ID: <5357e62e-2b42-41bc-8c63-1bafdb461e99@o2.pl>
Date:   Wed, 22 Nov 2023 18:06:05 +0100
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v2 3/4] rtc: Add support for configuring the UIP timeout
 for RTC reads
Content-Language: en-GB
To:     Mario Limonciello <mario.limonciello@amd.com>,
        Alessandro Zummo <a.zummo@towertech.it>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc:     "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        <linux-rtc@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-pm@vger.kernel.org, tobrohl@gmail.com, aalsing@gmail.com,
        Dhaval.Giani@amd.com, xmb8dsv4@gmail.com, x86@kernel.org,
        dhaval.giani@gmail.com
References: <20231120141555.458-1-mario.limonciello@amd.com>
 <20231120141555.458-4-mario.limonciello@amd.com>
From:   =?UTF-8?Q?Mateusz_Jo=C5=84czyk?= <mat.jonczyk@o2.pl>
Autocrypt: addr=mat.jonczyk@o2.pl; keydata=
 xsFNBFqMDyQBEAC2VYhOvwXdcGfmMs9amNUFjGFgLixeS2C1uYwaC3tYqjgDQNo/qDoPh52f
 ExoTMJRqx48qvvY/i6iwia7wOTBxbYCBDqGYxDudjtL41ko8AmbGOSkxJww5X/2ZAtFjUJxO
 QjNESFlRscMfDv5vcCvtH7PaJJob4TBZvKxdL4VCDCgEsmOadTy5hvwv0rjNjohau1y4XfxU
 DdvOcl6LpWMEezsHGc/PbSHNAKtVht4BZYg66kSEAhs2rOTN6pnWJVd7ErauehrET2xo2JbO
 4lAv0nbXmCpPj37ZvURswCeP8PcHoA1QQKWsCnHU2WeVw+XcvR/hmFMI2QnE6V/ObHAb9bzg
 jxSYVZRAWVsdNakfT7xhkaeHjEQMVRQYBL6bqrJMFFXyh9YDj+MALjyb5hDG3mUcB4Wg7yln
 DRrda+1EVObfszfBWm2pC9Vz1QUQ4CD88FcmrlC7n2witke3gr38xmiYBzDqi1hRmrSj2WnS
 RP/s9t+C8M8SweQ2WuoVBLWUvcULYMzwy6mte0aSA8XV6+02a3VuBjP/6Y8yZUd0aZfAHyPi
 Rf60WVjYNRSeg27lZ9DJmHjSfZNn1FrtZi3W9Ff6bry/SY9D136qXBQxPYxXQfaGDhVeLUVF
 Q+NIZ6NEjqrLQ07LEvUW2Qzk2q851/IaXZPtP6swx0gqrpjNrwARAQABzSRNYXRldXN6IEpv
 xYRjenlrIDxtYXQuam9uY3p5a0BvMi5wbD7CwX4EEwECACgFAlqMDyQCGwMFCRLMAwAGCwkI
 BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEPvWWrhhCv7Gb0MQAJVIpJ1KAOH6WaT8e65xZulI
 1jkwGwNp+3bWWc5eLjKUnXtOYpa9oIsUUAqvh/L8MofGtM1V11kSX9dEloyqlqDyNSQk0h52
 hZxMsCQyzjGOcBAi0zmWGYB4xu6SXj4LpVpIPW0sogduEOfbC0i7uAIyotHgepQ8RPGmZoXU
 9bzFCyqZ8kAqwOoCCx+ccnXtbnlAXQmDb88cIprAU+Elk4k4t7Bpjn2ek4fv35PsvsBdRTq3
 ADg8sGuq4KQXhbY53n1tyiab3M88uv6Cv//Ncgx+AqMdXq2AJ7amFsYdvkTC98sx20qk6Cul
 oHggmCre4MBcDD4S0qDXo5Z9NxVR/e9yUHxGLc5BlNj+FJPO7zwvkmIaMMnMlbydWVke0FSR
 AzJaEV/NNZKYctw2wYThdXPiz/y7aKd6/sM1jgPlleQhs3tZAIdjPfFjGdeeggv668M7GmKl
 +SEzpeFQ4b0x64XfLfLXX8GP/ArTuxEfJX4L05/Y9w9AJwXCVEwW4q17v8gNsPyVUVEdIroK
 cve6cgNNSWoxTaYcATePmkKnrAPqfg+6qFM4TuOWmyzCLQ1YoUZMxH+ddivDQtlKCp6JgGCz
 c9YCESxVii0vo8TsHdIAjQ/px9KsuYBmOlKnHXKbj6BsE/pkMMKQg/L415dvKzhLm2qVih7I
 U16IAtK5b7RpzsFNBFqMDyQBEACclVvbzpor4XfU6WLUofqnO3QSTwDuNyoNQaE4GJKEXA+p
 Bw5/D2ruHhj1Bgs6Qx7G4XL3odzO1xT3Iz6w26ZrxH69hYjeTdT8VW4EoYFvliUvgye2cC01
 ltYrMYV1IBXwJqSEAImU0Xb+AItAnHA1NNUUb9wKHvOLrW4Y7Ntoy1tp7Vww2ecAWEIYjcO6
 AMoUX8Q6gfVPxVEQv1EpspSwww+x/VlDGEiiYO4Ewm4MMSP4bmxsTmPb/f/K3rv830ZCQ5Ds
 U0rzUMG2CkyF45qXVWZ974NqZIeVCTE+liCTU7ARX1bN8VlU/yRs/nP2ISO0OAAMBKea7slr
 mu93to9gXNt3LEt+5aVIQdwEwPcqR09vGvTWdRaEQPqgkOJFyiZ0vYAUTwtITyjYxZWJbKJh
 JFaHpMds9kZLF9bH45SGb64uZrrE2eXTyI3DSeUS1YvMlJwKGumRTPXIzmVQ5PHiGXr2/9S4
 16W9lBDJeHhmcVOsn+04x5KIxHtqAP3mkMjDBYa0A3ksqD84qUBNuEKkZKgibBbs4qT35oXf
 kgWJtW+JziZf6LYx4WvRa80VDIIYCcQM6TrpsXIJI+su5qpzON1XJQG2iswY8PJ40pkRI9Sm
 kfTFrHOgiTpwZnI9saWqJh2ABavtnKZ1CtAY2VA8gmEqQeqs2hjdiNHAmRxR2wARAQABwsFl
 BBgBAgAPBQJajA8kAhsMBQkSzAMAAAoJEPvWWrhhCv7GhpYP/1tH/Kc35OgWu2lsgJxR9Z49
 4q+yYAuu11p0aQidL5utMFiemYHvxh/sJ4vMq65uPQXoQ3vo8lu9YR/p8kEt8jbljJusw6xQ
 iKA1Cc68xtseiKcUrjmN/rk3csbT+Qj2rZwkgod8v9GlKo6BJXMcKGbHb1GJtLF5HyI1q4j/
 zfeu7G1gVjGTx8e2OLyuBJp0HlFXWs2vWSMesmZQIBVNyyL9mmDLEwO4ULK2quF6RYtbvg+2
 PMyomNAaQB4s1UbXAO87s75hM79iszIzak2am4dEjTx+uYCWpvcw3rRDz7aMs401CphrlMKr
 WndS5qYcdiS9fvAfu/Jp5KIawpM0tVrojnKWCKHG4UnJIn+RF26+E7bjzE/Q5/NpkMblKD/Y
 6LHzJWsnLnL1o7MUARU++ztOl2Upofyuj7BSath0N632+XCTXk9m5yeDCl/UzPbP9brIChuw
 gF7DbkdscM7fkYzkUVRJM45rKOupy5Z03EtAzuT5Z/If3qJPU0txAJsquDohppFsGHrzn/X2
 0nI2LedLnIMUWwLRT4EvdYzsbP6im/7FXps15jaBOreobCaWTWtKtwD2LNI0l9LU9/RF+4Ac
 gwYu1CerMmdFbSo8ZdnaXlbEHinySUPqKmLHmPgDfxKNhfRDm1jJcGATkHCP80Fww8Ihl8aS
 TANkZ3QqXNX2
In-Reply-To: <20231120141555.458-4-mario.limonciello@amd.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

W dniu 20.11.2023 o 15:15, Mario Limonciello pisze:
> The UIP timeout is hardcoded to 10ms for all RTC reads, but in some
> contexts this might not be enough time. Add a timeout parameter to
> mc146818_get_time() and mc146818_get_time_callback().
>
> If UIP timeout is configured by caller to be >=100 ms and a call
> takes this long, log a warning.
>
> Make all callers use 10ms to ensure no functional changes.
>
> Cc: stable@vger.kernel.org # 6.1.y: commit d2a632a8a117 ("rtc: mc146818-lib: reduce RTC_UIP polling period")

I was wrong and
commit d2a632a8a117 ("rtc: mc146818-lib: reduce RTC_UIP polling period") is
included in 6.1.y anyway (was merged before 6.1-rc1), does not have to be
mentioned in the line above.

> Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v1->v2:
>  * Add a warning if 100ms or more
>  * Add stable and fixes tags
> ---
[snip]
> @@ -72,6 +76,9 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>  		}
>  		spin_unlock_irqrestore(&rtc_lock, flags);
>  
> +		if (i >= UIP_RECHECK_TIMEOUT_MS(100))
> +			pr_warn("RTC took %d iterations to clear UIP\n", i);
> +
This warning message is difficult to understand for someone that is not familiar
with
the code / MC146818 documentation.
"Reading current time from RTC took around %d ms" would be better.
>  		return true;
>  	}
>  	return false;

Greetings,

Mateusz