Messages in this thread | | | Date | Tue, 01 Sep 2015 14:54:17 +0300 | From | Mathias Nyman <> | Subject | Re: [PATCH v7 1/2] usb: make xhci platform driver use 64 bit or 32 bit DMA |
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On 31.08.2015 21:58, Duc Dang wrote: > On Thu, Aug 20, 2015 at 12:38 PM, Duc Dang <dhdang@apm.com> wrote: >> 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. >> >> [dhdang: regenerate the patch over 4.2-rc5 and address new comments] >> Signed-off-by: Mark Langsdorf <mlangsdo@redhat.com> >> Tested-by: Mark Salter <msalter@redhat.com> >> Signed-off-by: Duc Dang <dhdang@apm.com> >> >> --- >> Changes from v6: >> -Add WARN_ON if dma_mask is NULL >> -Use dma_coerce_mask_and_coherent to assign >> dma_mask and coherent_dma_mask >> >> Changes from v5: >> -Change comment >> -Assign dma_mask to coherent_dma_mask if dma_mask is NULL >> to make sure dma_set_mask_and_coherent does not fail prematurely. >> >> Changes from v4: >> -None >> >> Changes from v3: >> -Re-generate the patch over 4.2-rc5 >> -No code change. >> >> 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 | 21 +++++++++++++-------- >> 1 file changed, 13 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c >> index 890ad9d..e4c7f9d 100644 >> --- a/drivers/usb/host/xhci-plat.c >> +++ b/drivers/usb/host/xhci-plat.c >> @@ -93,14 +93,19 @@ static int xhci_plat_probe(struct platform_device *pdev) >> if (irq < 0) >> return -ENODEV; >> >> - /* 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)); >> + /* Throw a waring if broken platform code didn't initialize dma_mask */ >> + WARN_ON(!pdev->dev.dma_mask); >> + /* >> + * Try setting dma_mask and coherent_dma_mask to 64 bits, >> + * then try 32 bits >> + */ >> + ret = dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)); >> + if (ret) { >> + ret = dma_coerce_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) >> -- >> 1.9.1 >> > > Hi Greg, Arnd, Russell, > > Do you have any more comment about this patch set? >
I'm not sure I fully understand why we need to try the 64 bit DMA mask in platform probe.
As I understood it we just want to have some DMA mask set before calling usb_create_hcd() to make sure USB core gets the "uses_dma" flag set and dma_set_mask() won't fail because of missing dev->dma_mask.
The correct DMA mask is set later in xhci_gen_setup()
We also need to make sure the controller supports 64bit addressing capability before setting a 64 bit DMA mask. (bit 0 in HCCPARAMS)
So for platform devices it goes look go this:
xhci_plat_probe() usb_create_hcd() usb_create_shared_hcd() hcd->self.uses_dma = (dev->dma_mask != NULL); usb_add_hcd() hcd->driver->reset() (.reset = xhci_plat_setup) xhci_plat_setup() xhci_gen_setup() 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)); }
or do we end up with dev->dma_mask = NULL on 64-bit DMA only after trying to set it to 32 in xhci_plat_probe(), and thus also failing the dma_set_mask() in xhci_gen_setup()?
-Mathias
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