linux-kernel - Re: [PATCH] i2c: i2c-cadence: Don't register the adapter until it's ready

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Date:   Fri, 6 Jan 2017 23:34:24 +0200
From:   Vladimir Zapolskiy <vz@...ia.com>
To:     Mike Looijmans <mike.looijmans@...ic.nl>, linux-i2c@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        wsa@...-dreams.de, soren.brinkmann@...inx.com,
        michal.simek@...inx.com
Subject: Re: [PATCH] i2c: i2c-cadence: Don't register the adapter until it's
 ready

Hello Mike,

On 01/05/2017 12:47 PM, Mike Looijmans wrote:
> The driver calls i2c_add_adapter before writing to config registers,
> resulting in dmesg output like this, where devices fail to initialize:
> 
> cdns-i2c ff030000.i2c: timeout waiting on completion
> pca953x 1-0041: failed reading register
> pca953x: probe of 1-0041 failed with error -110
> at24 1-0050: 512 byte 24c04 EEPROM, writable, 1 bytes/write
> cdns-i2c ff030000.i2c: 100 kHz mmio ff030000 irq 197
> 
> The adapter is being used before it completed the "probe". To fix
> this, make "i2c_add_adapter" the last thing it calls in probe.
> It also makes sense to show the adapter initialization before
> the devices on the bus.

commonly "it also" in a commit message means a change, which should be done
separately, and this is the case here as well.

Because the adapter registration i2c_add_adapter() can fail, information
about the adapter initialization would be expected only in case of
successful registration.

The information sent to the kernel log buffer here is quite trivial,
probably dev_info() can be just removed, but in any case it should be
a separate change.

> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>

--
With best wishes,
Vladimir