linux-kernel - Re: [PATCH] i2c: designware: Use standard optional ref clock implementation

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Date:   Fri, 10 Jun 2022 16:31:16 +0300
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jan Dabros <jsd@...ihalf.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Gareth Williams <gareth.williams.jx@...esas.com>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: designware: Use standard optional ref clock
 implementation

On 6/10/22 14:19, Andy Shevchenko wrote:
> On Fri, Jun 10, 2022 at 10:42:33AM +0300, Serge Semin wrote:
>> Even though the DW I2C controller reference clock source is requested by
>> the method devm_clk_get() with non-optional clock requirement the way the
>> clock handler is used afterwards has a pure optional clock semantic
>> (though in some circumstances we can get a warning about the clock missing
>> printed in the system console). There is no point in reimplementing that
>> functionality seeing the kernel clock framework already supports the
>> optional interface from scratch. Thus let's convert the platform driver to
>> using it.
>>
>> Note by providing this commit we get to fix two problems. The first one
>> was introduced in commit c62ebb3d5f0d ("i2c: designware: Add support for
>> an interface clock"). It causes not having the interface clock (pclk)
>> enabled/disabled in case if the reference clock isn't provided. The second
>> problem was first introduced in commit b33af11de236 ("i2c: designware: Do
>> not require clock when SSCN and FFCN are provided"). Since that
>> modification the deferred probe procedure has been unsupported in case if
>> the interface clock isn't ready.
> 
> Makes sense,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
Acked-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>