> From: Matthijs Kooijman [mailto:matthijs@xxxxxxxx] > Sent: Monday, April 29, 2013 7:33 AM > > Instead of just setting the dma_mask to the empty mask, the pointer to > the mask is cleared altogether. This is needed because > usb_create_shared_hcd sets hcd->self.uses_dma based on > dev->dma_mask != NULL, not by looking at the actual mask itself. > > This change thus makes hcd->self.uses_dma have the correct value when > not using dma even though a dma_mask was set up by the platform or pci > driver (which in practice should only occur when manually disabling > dma, assuming that a dma_mask is normally only setup when dma is > supported and enabled). This in turn prevents usb core from doing some > dma-specific stuff that isn't needed (though everything seemed to work > with the wrong value of uses_dma as well). > > Signed-off-by: Matthijs Kooijman <matthijs@xxxxxxxx> > --- > drivers/staging/dwc2/hcd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/staging/dwc2/hcd.c b/drivers/staging/dwc2/hcd.c > index 7727112..ac34d4a 100644 > --- a/drivers/staging/dwc2/hcd.c > +++ b/drivers/staging/dwc2/hcd.c > @@ -2810,7 +2810,7 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq, > dev_warn(hsotg->dev, > "can't enable workaround for >2GB RAM\n"); > } else { > - dma_set_mask(hsotg->dev, 0); > + hsotg->dev->dma_mask = NULL; > dma_set_coherent_mask(hsotg->dev, 0); > } Hi Matthijs, I see a problem after applying this patch. If I insert the driver modules with dwc2_module_params.dma_enable = 0, remove the modules, then insert them again with dwc2_module_params.dma_enable = 1, then the DMA does not get enabled. I see the message "dma_mask not set, disabling DMA" from the other patch. So setting the hsotg->dev->dma_mask pointer to NULL seems to be irreversible. It seems like this shouldn't happen. I think hsotg->dev should get deleted when the module is removed, and recreated when it is inserted again. But maybe I just don't understand the device model. -- Paul -- 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
