Hi Mark, > -----Original Message----- > From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Langsdorf > Sent: Wednesday, November 26, 2014 6:19 AM > To: linux-usb@xxxxxxxxxxxxxxx; mathias.nyman@xxxxxxxxx > Cc: mlangsdo@xxxxxxxxxx > Subject: [PATCH v3 1/2] make xhci platform driver use 64 bit or 32 bit DMA > > The xhci platform driver needs to work on systems that either only > support 64-bit DMA or only support 32-bit DMA. Attempt to set a > coherent dma mask for 64-bit DMA, and attempt again with 32-bit > DMA if that fails. I'm afraid but I have a comment about this patch. Since my environment (It's R-Car Gen2. It has ARM/CA15 and LPAE) has a restriction about DMA coherent, I intend to send some patches to avoid the restriction. And then, I found this patch. About my environment restriction is: - R-Car Gen2 can use LAPE. - So, dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)); will not fail. - AXI address bus width of R-Car Gen2 xHCI controller is 32 bit. - However, The HCCPARAMS.AC64 is set to 1. So, in this environment, I think the xHCI driver should call dma_set_coherent(dev, DMA_BIT_MASK(32)) because AXI address bus width is 32 bit. However, in this case, the xHCI driver will call dma_set_coherent_mask(dev, DMA_BIT_MASK(64)) in line 4900 of drivers/usb/host/xhci.c: /* Set dma_mask and coherent_dma_mask to 64-bits, * if xHC supports 64-bit addressing */ if (HCC_64BIT_ADDR(xhci->hcc_params) && !dma_set_mask(dev, DMA_BIT_MASK(64))) { xhci_dbg(xhci, "Enabling 64-bit DMA addresses.\n"); dma_set_coherent_mask(dev, DMA_BIT_MASK(64)); } So, I intend to send some patches to add a quirk to this condition. However, if this patch is applied, I also need more patch for xhci-plat.c. Or, I misunderstand about the DMA-API? Best regards, Yoshihiro Shimoda > Signed-off-by: Mark Langsdorf <mlangsdo@xxxxxxxxxx> > Tested-by: Mark Salter <msalter@xxxxxxxxxx> > --- > Changes from v2: > None > Changes from v1: > Consolidated to use dma_set_mask_and_coherent > Got rid of the check against sizeof(dma_addr_t) > > drivers/usb/host/xhci-plat.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c > index 3d78b0c..34cbf65 100644 > --- a/drivers/usb/host/xhci-plat.c > +++ b/drivers/usb/host/xhci-plat.c > @@ -96,14 +96,14 @@ static int xhci_plat_probe(struct platform_device *pdev) > return ret; > } > > - /* Initialize dma_mask and coherent_dma_mask to 32-bits */ > - ret = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32)); > - if (ret) > - return ret; > - if (!pdev->dev.dma_mask) > - pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask; > - else > - dma_set_mask(&pdev->dev, DMA_BIT_MASK(32)); > + /* Try setting the coherent_dma_mask to 64 bits, then try 32 bits */ > + ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)); > + if (ret) { > + ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)); > + if (ret) > + return ret; > + } > + > > hcd = usb_create_hcd(driver, &pdev->dev, dev_name(&pdev->dev)); > if (!hcd) > -- > 1.9.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-usb" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
