linux-kernel - Re: [RFC PATCH] USB: PCI: set 32bit DMA mask for PCI based USB controllers

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Date:   Wed, 30 Jan 2019 08:40:59 +0100
From:   Christoph Hellwig <hch@....de>
To:     Hanjun Guo <guohanjun@...wei.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Christoph Hellwig <hch@....de>, linux-usb@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        John Garry <john.garry@...wei.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        anthony.jebson@...wei.com, Hanjun Guo <hanjun.guo@...aro.org>
Subject: Re: [RFC PATCH] USB: PCI: set 32bit DMA mask for PCI based USB
 controllers

On Wed, Jan 30, 2019 at 03:01:54PM +0800, Hanjun Guo wrote:
> This is the RFC version, I'm not sure this is the best solution,
> comments are warmly welcomed.
> 
> Thanks
> Hanjun
> 
>  drivers/usb/core/hcd-pci.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
> index 0343246..a9c33e6 100644
> --- a/drivers/usb/core/hcd-pci.c
> +++ b/drivers/usb/core/hcd-pci.c
> @@ -188,6 +188,10 @@ int usb_hcd_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  	if (pci_enable_device(dev) < 0)
>  		return -ENODEV;
>  
> +	retval = dma_coerce_mask_and_coherent(&dev->dev, DMA_BIT_MASK(32));
> +	if (retval)
> +		return retval;

dma_coerce_mask_and_coherent is only for platform devices (and I'm
not sure it is a good idea to start with, but that is a different
story).

PCI device should have the dma_mask pointer set already, so you should
use dma_set_mask_and_coherent here.