Re: [PATCH] mfd: wcd934x: set DMA mask on parent to silence "DMA mask not set"

[Lee Jones]

On Sun, 23 Aug 2026, David Heidelberg via B4 Relay wrote:

> From: David Heidelberg <david@xxxxxxx>
> 
> The wcd934x MFD parent (a slim_device) never initializes its
> dma_mask/coherent_dma_mask. When the DT-aware children pass through
> of_dma_configure() this triggers the "DMA mask not set" warning for
> each child.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: f959dcd6ddfd ("dma-direct: Fix potential NULL pointer dereference")
> Assisted-by: tencent:hy3
> Signed-off-by: David Heidelberg <david@xxxxxxx>
> ---
>  drivers/mfd/wcd934x.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/mfd/wcd934x.c b/drivers/mfd/wcd934x.c
> index 3c3080e8c8cf7..70ee13791d52b 100644
> --- a/drivers/mfd/wcd934x.c
> +++ b/drivers/mfd/wcd934x.c
> @@ -1,12 +1,13 @@
>  // SPDX-License-Identifier: GPL-2.0
>  // Copyright (c) 2019, Linaro Limited
>  
>  #include <linux/clk.h>
> +#include <linux/dma-mapping.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/interrupt.h>
>  #include <linux/kernel.h>
>  #include <linux/mfd/core.h>
>  #include <linux/mfd/wcd934x/registers.h>
>  #include <linux/mfd/wcd934x/wcd934x.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> @@ -212,16 +213,21 @@ static int wcd934x_slim_status(struct slim_device *sdev,
>  static int wcd934x_slim_probe(struct slim_device *sdev)
>  {
>  	struct device *dev = &sdev->dev;
>  	struct device_node *np = dev->of_node;
>  	struct wcd934x_ddata *ddata;
>  	struct gpio_desc *reset_gpio;
>  	int ret;
>  
> +	if (!dev->dma_mask) {
> +		dev->dma_mask = &dev->coherent_dma_mask;
> +		dev->coherent_dma_mask = DMA_BIT_MASK(32);
> +	}
> +

Any reason not to use dma_coerce_mask_and_coherent()?

>  	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
>  	if (!ddata)
>  		return	-ENOMEM;
>  
>  	ddata->irq = of_irq_get(np, 0);
>  	if (ddata->irq < 0)
>  		return dev_err_probe(ddata->dev, ddata->irq,
>  				     "Failed to get IRQ\n");
> 
> ---
> base-commit: 7079a12d7506b07fb53b54a664bfad5fa9b16d70
> change-id: 20260823-wcd-dma-bd621ee39887
> 
> Best regards,
> --  
> David Heidelberg <david@xxxxxxx>
> 
> 

-- 
Lee Jones