From: Wolfram Sang <wsa@kernel.org>
To: "Martin Povišer" <povik+lin@cutebit.org>
Cc: Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
Michael Ellerman <mpe@ellerman.id.au>,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Jean Delvare <khali@linux-fr.org>,
Olof Johansson <olof@lixom.net>,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, Janne Grunau <j@jannau.net>
Subject: Re: [PATCH] i2c: pasemi: Wait for write xfers to finish
Date: Fri, 15 Apr 2022 23:12:28 +0200 [thread overview]
Message-ID: <YlnfvJDyluEDfu39@shikoro> (raw)
In-Reply-To: <20220329183817.21656-1-povik+lin@cutebit.org>
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On Tue, Mar 29, 2022 at 08:38:17PM +0200, Martin Povišer wrote:
> Wait for completion of write transfers before returning from the driver.
> At first sight it may seem advantageous to leave write transfers queued
> for the controller to carry out on its own time, but there's a couple of
> issues with it:
>
> * Driver doesn't check for FIFO space.
>
> * The queued writes can complete while the driver is in its I2C read
> transfer path which means it will get confused by the raising of
> XEN (the 'transaction ended' signal). This can cause a spurious
> ENODATA error due to premature reading of the MRXFIFO register.
>
> Adding the wait fixes some unreliability issues with the driver. There's
> some efficiency cost to it (especially with pasemi_smb_waitready doing
> its polling), but that will be alleviated once the driver receives
> interrupt support.
>
> Fixes: beb58aa39e6e ("i2c: PA Semi SMBus driver")
> Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Applied to for-current, thanks!
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WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@kernel.org>
To: "Martin Povišer" <povik+lin@cutebit.org>
Cc: Sven Peter <sven@svenpeter.dev>, Hector Martin <marcan@marcan.st>,
linux-kernel@vger.kernel.org, Olof Johansson <olof@lixom.net>,
Paul Mackerras <paulus@samba.org>,
linux-arm-kernel@lists.infradead.org,
Jean Delvare <khali@linux-fr.org>, Janne Grunau <j@jannau.net>,
linuxppc-dev@lists.ozlabs.org,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
linux-i2c@vger.kernel.org
Subject: Re: [PATCH] i2c: pasemi: Wait for write xfers to finish
Date: Fri, 15 Apr 2022 23:12:28 +0200 [thread overview]
Message-ID: <YlnfvJDyluEDfu39@shikoro> (raw)
In-Reply-To: <20220329183817.21656-1-povik+lin@cutebit.org>
[-- Attachment #1: Type: text/plain, Size: 1045 bytes --]
On Tue, Mar 29, 2022 at 08:38:17PM +0200, Martin Povišer wrote:
> Wait for completion of write transfers before returning from the driver.
> At first sight it may seem advantageous to leave write transfers queued
> for the controller to carry out on its own time, but there's a couple of
> issues with it:
>
> * Driver doesn't check for FIFO space.
>
> * The queued writes can complete while the driver is in its I2C read
> transfer path which means it will get confused by the raising of
> XEN (the 'transaction ended' signal). This can cause a spurious
> ENODATA error due to premature reading of the MRXFIFO register.
>
> Adding the wait fixes some unreliability issues with the driver. There's
> some efficiency cost to it (especially with pasemi_smb_waitready doing
> its polling), but that will be alleviated once the driver receives
> interrupt support.
>
> Fixes: beb58aa39e6e ("i2c: PA Semi SMBus driver")
> Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Applied to for-current, thanks!
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WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@kernel.org>
To: "Martin Povišer" <povik+lin@cutebit.org>
Cc: Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
Michael Ellerman <mpe@ellerman.id.au>,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Jean Delvare <khali@linux-fr.org>,
Olof Johansson <olof@lixom.net>,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, Janne Grunau <j@jannau.net>
Subject: Re: [PATCH] i2c: pasemi: Wait for write xfers to finish
Date: Fri, 15 Apr 2022 23:12:28 +0200 [thread overview]
Message-ID: <YlnfvJDyluEDfu39@shikoro> (raw)
In-Reply-To: <20220329183817.21656-1-povik+lin@cutebit.org>
[-- Attachment #1.1: Type: text/plain, Size: 1045 bytes --]
On Tue, Mar 29, 2022 at 08:38:17PM +0200, Martin Povišer wrote:
> Wait for completion of write transfers before returning from the driver.
> At first sight it may seem advantageous to leave write transfers queued
> for the controller to carry out on its own time, but there's a couple of
> issues with it:
>
> * Driver doesn't check for FIFO space.
>
> * The queued writes can complete while the driver is in its I2C read
> transfer path which means it will get confused by the raising of
> XEN (the 'transaction ended' signal). This can cause a spurious
> ENODATA error due to premature reading of the MRXFIFO register.
>
> Adding the wait fixes some unreliability issues with the driver. There's
> some efficiency cost to it (especially with pasemi_smb_waitready doing
> its polling), but that will be alleviated once the driver receives
> interrupt support.
>
> Fixes: beb58aa39e6e ("i2c: PA Semi SMBus driver")
> Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Applied to for-current, thanks!
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next prev parent reply other threads:[~2022-04-15 21:12 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-29 18:38 [PATCH] i2c: pasemi: Wait for write xfers to finish Martin Povišer
2022-03-29 18:38 ` Martin Povišer
2022-03-29 18:38 ` Martin Povišer
2022-03-29 19:58 ` Sven Peter
2022-03-29 19:58 ` Sven Peter
2022-03-29 19:58 ` Sven Peter
2022-04-15 21:12 ` Wolfram Sang [this message]
2022-04-15 21:12 ` Wolfram Sang
2022-04-15 21:12 ` Wolfram Sang
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