linux-kernel - Re: [PATCH] Revert "of/device: Really only set bus DMA mask when appropriate"

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Date:   Thu, 28 Feb 2019 14:39:47 -0800 (PST)
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     Alistair Francis <Alistair.Francis@....com>
cc:     "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alistair23@...il.com" <alistair23@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "of/device: Really only set bus DMA mask when
 appropriate"

Hello Alistair,

On Thu, 28 Feb 2019, Alistair Francis wrote:

> This reverts commit 6778be4e520959659b27a441c06a84c9cb009085.
> 
> Reverting the commit fixes these error messages and an non-functioning
> USB bus when attaching a USB to PCIe card to a RISC-V board:
>     xhci_hcd 0000:03:00.0: Host took too long to start, waited 16000 microseconds.
>     xhci_hcd 0000:03:00.0: startup error -19
>     xhci_hcd 0000:03:00.0: USB bus 2 deregistered
>     xhci_hcd 0000:03:00.0: WARNING: Host System Error
>     xhci_hcd 0000:03:00.0: remove, state 1
> 
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> ---
> I'm not sure if this is the correct fix, it's possible something else is
> wrong, but I wanted to get some feedback.
> 
> drivers/of/device.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index 3717f2a20d0d..8299f8055da7 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -149,11 +149,9 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
>  	 * set by the driver.
>  	 */
>  	mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1);
> +	dev->bus_dma_mask = mask;
>  	dev->coherent_dma_mask &= mask;
>  	*dev->dma_mask &= mask;
> -	/* ...but only set bus mask if we found valid dma-ranges earlier */

Does the DT data for the PCIe controller that you're using contain a 
dma-ranges node?

> -	if (!ret)
> -		dev->bus_dma_mask = mask;
>  
>  	coherent = of_dma_is_coherent(np);
>  	dev_dbg(dev, "device is%sdma coherent\n",


- Paul