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From: David Miller <>
Subject: Re: [PATCH 2/2] net: dsa: microchip: Add shared regmap mutex
Date: Sun, 13 Oct 2019 09:26:28 -0700 (PDT)
Message-ID: <> (raw)
In-Reply-To: <>

From: Marek Vasut <>
Date: Sun, 13 Oct 2019 12:50:15 +0200

> On 10/13/19 2:21 AM, David Miller wrote:
>> From: David Miller <>
>> Date: Sat, 12 Oct 2019 17:20:55 -0700 (PDT)
>>> From: Marek Vasut <>
>>> Date: Thu, 10 Oct 2019 20:25:08 +0200
>>>> The KSZ driver uses one regmap per register width (8/16/32), each with
>>>> it's own lock, but accessing the same set of registers. In theory, it
>>>> is possible to create a race condition between these regmaps, although
>>>> the underlying bus (SPI or I2C) locking should assure nothing bad will
>>>> really happen and the accesses would be correct.
>>>> To make the driver do the right thing, add one single shared mutex for
>>>> all the regmaps used by the driver instead. This assures that even if
>>>> some future hardware is on a bus which does not serialize the accesses
>>>> the same way SPI or I2C does, nothing bad will happen.
>>>> Note that the status_mutex was unused and only initied, hence it was
>>>> renamed and repurposed as the regmap mutex.
>>>> Signed-off-by: Marek Vasut <>
>>> Applied.
>> Actually, both patches reverted.  Please test your changes properly:
>> ERROR: "ksz_regmap_unlock" [drivers/net/dsa/microchip/ksz8795_spi.ko] undefined!
>> ERROR: "ksz_regmap_lock" [drivers/net/dsa/microchip/ksz8795_spi.ko] undefined!
>> ERROR: "ksz_regmap_unlock" [drivers/net/dsa/microchip/ksz9477_spi.ko] undefined!
>> ERROR: "ksz_regmap_lock" [drivers/net/dsa/microchip/ksz9477_spi.ko] undefined!
>> ERROR: "ksz_regmap_unlock" [drivers/net/dsa/microchip/ksz9477_i2c.ko] undefined!
>> ERROR: "ksz_regmap_lock" [drivers/net/dsa/microchip/ksz9477_i2c.ko] undefined!
> So the test is to compile it as a module ?

The test is to compile it in all relevant possible configurations.

As a module, statically, and with dependent modules both static and
modular as is relevant.

  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10 18:25 [PATCH 1/2] net: dsa: microchip: Do not reinit mutexes on KSZ87xx Marek Vasut
2019-10-10 18:25 ` [PATCH 2/2] net: dsa: microchip: Add shared regmap mutex Marek Vasut
2019-10-13  0:20   ` David Miller
2019-10-13  0:21     ` David Miller
2019-10-13 10:50       ` Marek Vasut
2019-10-13 16:26         ` David Miller [this message]
2019-10-13  0:20 ` [PATCH 1/2] net: dsa: microchip: Do not reinit mutexes on KSZ87xx David Miller

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