linux-kernel - Re: [PATCH] mfd: mfd-core: Don't overwrite the dma

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Message-ID: <20200605131622.GL2428291@smile.fi.intel.com>
Date:   Fri, 5 Jun 2020 16:16:22 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Gene Chen <gene.chen.richtek@...il.com>
Subject: Re: [PATCH] mfd: mfd-core: Don't overwrite the dma_mask of the child
 device

On Thu, Jun 04, 2020 at 11:30:37PM +0200, Michael Walle wrote:
> Commit cdfee5623290 ("driver core: initialize a default DMA mask for
> platform device") initialize the DMA of a platform device. But if the
> parent doesn't have a dma_mask set, for example if it's an I2C device,
> the dma_mask of the child platform device will be set to zero again.
> Which leads to many "DMA mask not set" warnings, if the MFD cell has the
> of_compatible property set.
> 
> [    1.877937] sl28cpld-pwm sl28cpld-pwm: DMA mask not set
> [    1.883282] sl28cpld-pwm sl28cpld-pwm.0: DMA mask not set
> [    1.888795] sl28cpld-gpio sl28cpld-gpio: DMA mask not set
> 
> Thus don't overwrite the dma_mask of the children. Instead set the
> dma_mask of the platform device.

> ---
> Former discussion was here:
> https://lore.kernel.org/lkml/20200423174543.17161-3-michael@walle.cc/
> 
> Because my MFD driver now uses of_platform_populate() it doesn't trigger
> this anymore. But it may be useful for others, e.g. if I'm not mistaken it
> should apply to the mt6360 sub devices.

Yeah, I'm not sure it's right thing to do, but let maintainers and more
experienced in topic developers to speak up.

-- 
With Best Regards,
Andy Shevchenko