linux-kernel - Re: [PATCH 1/1] PCI: layerscape-ep: set 64-bit DMA mask

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Message-ID: <925da248-f582-6dd5-57ab-0fadc4e84f9e@wanadoo.fr>
Date:   Thu, 21 Sep 2023 19:59:51 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Frank Li <Frank.Li@....com>, Minghuan Lian <minghuan.Lian@....com>,
        Mingkai Hu <mingkai.hu@....com>, Roy Zang <roy.zang@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "open list:PCI DRIVER FOR FREESCALE LAYERSCAPE" 
        <linuxppc-dev@...ts.ozlabs.org>,
        "open list:PCI DRIVER FOR FREESCALE LAYERSCAPE" 
        <linux-pci@...r.kernel.org>,
        "moderated list:PCI DRIVER FOR FREESCALE LAYERSCAPE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     imx@...ts.linux.dev
Subject: Re: [PATCH 1/1] PCI: layerscape-ep: set 64-bit DMA mask

Le 21/09/2023 à 17:37, Frank Li a écrit :
> From: Guanhua Gao <guanhua.gao@....com>
> 
> Set DMA mask and coherent DMA mask to enable 64-bit addressing.
> 
> Signed-off-by: Guanhua Gao <guanhua.gao@....com>
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
>   drivers/pci/controller/dwc/pci-layerscape-ep.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-layerscape-ep.c b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> index de4c1758a6c33..6fd0dea38a32c 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape-ep.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> @@ -249,6 +249,11 @@ static int __init ls_pcie_ep_probe(struct platform_device *pdev)
>   
>   	pcie->big_endian = of_property_read_bool(dev->of_node, "big-endian");
>   
> +	/* set 64-bit DMA mask and coherent DMA mask */
> +	if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)))
> +		if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)))

As stated in [1], dma_set_mask() with a 64-bit mask will never
fail if dev->dma_mask is non-NULL.

So, if it fails, the 32 bits case will also fail for the same reason.
There is no need for the 2nd test.


See [1] for Christoph Hellwig comment about it.

CJ


[1]: https://lkml.org/lkml/2021/6/7/398

> +			return -EIO;
> +
>   	platform_set_drvdata(pdev, pcie);
>   
>   	ret = dw_pcie_ep_init(&pci->ep);