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

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Date:   Fri, 10 Jun 2022 14:19:26 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        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 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>

> Fixes: c62ebb3d5f0d ("i2c: designware: Add support for an interface clock")
> Fixes: b33af11de236 ("i2c: designware: Do not require clock when SSCN and FFCN are provided")
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> ---
>  drivers/i2c/busses/i2c-designware-common.c  |  3 ---
>  drivers/i2c/busses/i2c-designware-platdrv.c | 13 +++++++++++--
>  2 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
> index 9f8574320eb2..b08e5bc2b64c 100644
> --- a/drivers/i2c/busses/i2c-designware-common.c
> +++ b/drivers/i2c/busses/i2c-designware-common.c
> @@ -477,9 +477,6 @@ int i2c_dw_prepare_clk(struct dw_i2c_dev *dev, bool prepare)
>  {
>  	int ret;
>  
> -	if (IS_ERR(dev->clk))
> -		return PTR_ERR(dev->clk);
> -
>  	if (prepare) {
>  		/* Optional interface clock */
>  		ret = clk_prepare_enable(dev->pclk);
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 70ade5306e45..ba043b547393 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -320,8 +320,17 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>  		goto exit_reset;
>  	}
>  
> -	dev->clk = devm_clk_get(&pdev->dev, NULL);
> -	if (!i2c_dw_prepare_clk(dev, true)) {
> +	dev->clk = devm_clk_get_optional(&pdev->dev, NULL);
> +	if (IS_ERR(dev->clk)) {
> +		ret = PTR_ERR(dev->clk);
> +		goto exit_reset;
> +	}
> +
> +	ret = i2c_dw_prepare_clk(dev, true);
> +	if (ret)
> +		goto exit_reset;
> +
> +	if (dev->clk) {
>  		u64 clk_khz;
>  
>  		dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
> -- 
> 2.35.1
> 

-- 
With Best Regards,
Andy Shevchenko