Re: [PATCH] i2c: imx: Initialize DMA before registering I2C adapter

[Andrey Smirnov]

On Sat, Jun 8, 2019 at 10:57 PM Andrey Smirnov <andrew.smirnov@xxxxxxxxx> wrote:
>
> Allocating DMA after registering I2C adapter can lead to infinite
> probing loop, for example, consider the following scenario:
>
>     1. i2c_imx_probe() is called and successfully registers an I2C
>        adapter via i2c_add_numbered_adapter()
>
>     2. As a part of i2c_add_numbered_adapter() new I2C slave devices
>        are added from DT which results in a call to
>        driver_deferred_probe_trigger()
>
>     3. i2c_imx_probe() continues and calls i2c_imx_dma_request() which
>        due to lack of proper DMA driver returns -EPROBE_DEFER
>
>     4. i2c_imx_probe() fails, removes I2C adapter and returns
>        -EPROBE_DEFER, which places it into deferred probe list
>
>     5. Deferred probe work triggered in #2 above kicks in and calls
>        i2c_imx_probe() again thus bringing us to step #1
>
> To avoid having this problem, move i2c_imx_dma_request() to happen
> before i2c_add_numbered_adapter().
>
> This problem was encountered on VF610 CFU1 board with
> CONFIG_FSL_EDMA=n.
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
> Cc: Chris Healy <cphealy@xxxxxxxxx>
> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> Cc: Fabio Estevam <festevam@xxxxxxxxx>
> Cc: NXP Linux Team <linux-imx@xxxxxxx>
> Cc: linux-i2c@xxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx

Gentle ping. Any feedback on this?

Thanks,
Andrey Smirnov