From: Wolfram Sang <wsa@kernel.org>
To: "Marek Behún" <kabel@kernel.org>
Cc: linux-i2c@vger.kernel.org,
Gregory CLEMENT <gregory.clement@bootlin.com>,
Samuel Holland <samuel@sholland.org>,
Chris Morgan <macromorgan@hotmail.com>,
Russell King <rmk+kernel@armlinux.org.uk>
Subject: Re: [PATCH] i2c: mv64xxx: Fix reading invalid status value in atomic mode
Date: Mon, 5 Jun 2023 12:23:06 +0200 [thread overview]
Message-ID: <ZH23iq1u5jEtsC8W@shikoro> (raw)
In-Reply-To: <20230521121940.27057-1-kabel@kernel.org>
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On Sun, May 21, 2023 at 02:19:40PM +0200, Marek Behún wrote:
> There seems to be a bug within the mv64xxx I2C controller, wherein the
> status register may not necessarily contain valid value immediately
> after the IFLG flag is set in the control register.
>
> My theory is that the controller:
> - first sets the IFLG in control register
> - then updates the status register
> - then raises an interrupt
>
> This may sometime cause weird bugs when in atomic mode, since in this
> mode we do not wait for an interrupt, but instead we poll the control
> register for IFLG and read status register immediately after.
>
> I encountered -ENXIO from mv64xxx_i2c_fsm() due to this issue when using
> this driver in atomic mode.
>
> Note that I've only seen this issue on Armada 385, I don't know whether
> other SOCs with this controller are also affected. Also note that this
> fix has been in U-Boot for over 4 years [1] without anybody complaining,
> so it should not cause regressions.
>
> [1] https://source.denx.de/u-boot/u-boot/-/commit/d50e29662f78
>
> Fixes: 544a8d75f3d6 ("i2c: mv64xxx: Add atomic_xfer method to driver")
> Signed-off-by: Marek Behún <kabel@kernel.org>
Applied to for-current, thanks!
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prev parent reply other threads:[~2023-06-05 10:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-21 12:19 [PATCH] i2c: mv64xxx: Fix reading invalid status value in atomic mode Marek Behún
2023-05-24 16:24 ` Chris Morgan
2023-06-05 10:23 ` Wolfram Sang [this message]
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