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From: Wolfram Sang <wsa@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yann Sionneau <ysionneau@kalrayinc.com>,
	Jan Bottorff <janb@os.amperecomputing.com>,
	Serge Semin <fancer.lancer@gmail.com>,
	Yann Sionneau <yann@sionneau.net>, Will Deacon <will@kernel.org>,
	Jarkko Nikula <jarkko.nikula@linux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Jan Dabros <jsd@semihalf.com>, Andi Shyti <andi.shyti@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] i2c: designware: Fix corrupted memory seen in the ISR
Date: Tue, 19 Sep 2023 16:55:29 +0200	[thread overview]
Message-ID: <ZQm2Ydt/0jRW4crK@shikoro> (raw)
In-Reply-To: <ZQm1UyZ0g7KxRW3a@arm.com>

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> OK, since it ends up with the *_relaxed() accessors, there are no
> barriers here. I wonder whether the regmap API should have both standard
> and relaxed variants. If a regmap driver does not populate the
> .reg_write_relaxed etc. members, a regmap_write_relaxed() would just
> fall back to regmap_write().
> 
> We went through similar discussions many years ago around the I/O
> accessors and decided to add the barriers to readl/writel() even if they
> become more expensive, correctness should be first. The relaxed variants
> were added as optimisations if specific memory ordering was not
> required. I think the regmap API should follow the same semantics, go
> for correctness first as you can't tell what the side-effect of a
> regmap_write() is (e.g. kicking off DMA or causing an interrupt on
> another CPU).

Again, I am all with Catalin here. Safety first, optimizations a la
*_relaxed should be opt-in.


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  reply	other threads:[~2023-09-19 14:55 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-13 23:29 [PATCH v2] i2c: designware: Fix corrupted memory seen in the ISR Jan Bottorff
2023-09-14 18:46 ` Andy Shevchenko
2023-09-14 18:47   ` Andy Shevchenko
2023-09-14 20:52     ` Jan Bottorff
2023-09-15 12:44 ` Jarkko Nikula
2023-09-15 15:21 ` Serge Semin
2023-09-16  1:47   ` Jan Bottorff
2023-09-17  0:01     ` Serge Semin
2023-09-17 20:08       ` Yann Sionneau
2023-09-18 23:14         ` Serge Semin
2023-09-19  3:45           ` Jan Bottorff
2023-09-19  9:55             ` Catalin Marinas
2023-09-19 10:19               ` Wolfram Sang
2023-09-19 12:38                 ` Yann Sionneau
2023-09-19 14:51                   ` Catalin Marinas
2023-09-19 14:55                     ` Wolfram Sang [this message]
2023-09-19 18:54                     ` Jan Bottorff
2023-09-19 21:05                       ` Serge Semin
2023-09-20  9:08                         ` Wolfram Sang
2023-09-20 13:27                           ` Yann Sionneau
2023-09-20 19:14                             ` Jan Bottorff
2023-09-25 12:54                               ` Serge Semin
2023-09-25 19:39                                 ` Jan Bottorff
2023-09-27 19:38                                   ` Wolfram Sang
2023-09-29  8:48                                     ` Jarkko Nikula
2023-10-26 11:18                                       ` Wolfram Sang
2023-10-31  0:12                                         ` Jan Bottorff
2023-10-31  5:51                                           ` Wolfram Sang
2023-10-31  8:44                                           ` Yann Sionneau
2023-10-31 12:10                                             ` Jarkko Nikula
2023-10-31 13:06                                               ` Serge Semin
2023-11-01 16:51                                                 ` Jan Bottorff
2023-09-20 11:03                         ` Catalin Marinas
2023-09-20 10:44                       ` Catalin Marinas
2023-09-20 11:05                         ` Catalin Marinas

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