Re: [PATCH] i2c: mv64xxx: Fix random system lock caused by runtime PM

[Wolfram Sang <wsa@kernel.org>]

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On Thu, Apr 08, 2021 at 04:00:00AM +0200, Marek Behún wrote:
> I noticed a weird bug with this driver on Marvell CN9130 Customer
> Reference Board.
> 
> Sometime after boot, the system locks with the following message:
>  [104.071363] i2c i2c-0: mv64xxx: I2C bus locked, block: 1, time_left: 0
> 
> The system does not respond afterwards, only warns about RCU stalls.
> 
> This first appeared with commit e5c02cf54154 ("i2c: mv64xxx: Add runtime
> PM support").
> 
> With further experimentation I discovered that adding a delay into
> mv64xxx_i2c_hw_init() fixes this issue. This function is called before
> every xfer, due to how runtime PM works in this driver. It seems that in
> order to work correctly, a delay is needed after the bus is reset in
> this function.
> 
> Since there already is a known erratum with this controller needing a
> delay, I assume that this is just another place this needs to be
> applied. Therefore I apply the delay only if errata_delay is true.
> 
> Signed-off-by: Marek Behún <kabel@kernel.org>

Applied to for-current, thanks!


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