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

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Message-Id: <20200604213037.17254-1-michael@walle.cc>
Date:   Thu,  4 Jun 2020 23:30:37 +0200
From:   Michael Walle <michael@...le.cc>
To:     linux-kernel@...r.kernel.org
Cc:     Lee Jones <lee.jones@...aro.org>, Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Robin Murphy <robin.murphy@....com>,
        Gene Chen <gene.chen.richtek@...il.com>,
        Michael Walle <michael@...le.cc>
Subject: [PATCH] mfd: mfd-core: Don't overwrite the dma_mask of the child device

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.

Signed-off-by: Michael Walle <michael@...le.cc>
Suggested-by: Robin Murphy <robin.murphy@....com>
---
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.

Thus I'm submitting this patch seperately.

 drivers/mfd/mfd-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index f5a73af60dd4..e735565969b3 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -138,7 +138,7 @@ static int mfd_add_device(struct device *parent, int id,

 	pdev->dev.parent = parent;
 	pdev->dev.type = &mfd_dev_type;
-	pdev->dev.dma_mask = parent->dma_mask;
+	pdev->platform_dma_mask = parent->dma_mask ? *parent->dma_mask : 0;
 	pdev->dev.dma_parms = parent->dma_parms;
 	pdev->dev.coherent_dma_mask = parent->coherent_dma_mask;

-- 
2.20.1