Re: [PATCH] usb: dwc3: core: leave default DMA if the controller does not support 64-bit DMA

[wuliangfeng]

On 2022/9/2 上午1:38, Sven Peter wrote:
> On Thu, Sep 1, 2022, at 10:34, William Wu wrote:
> > On some DWC3 controllers (e.g. Rockchip SoCs), the DWC3 core
> > doesn't support 64-bit DMA address width. In this case, this
> > driver should use the default 32-bit mask. Otherwise, the DWC3
> > controller will break if it runs on above 4GB physical memory
> > environment.
> >
> > This patch reads the DWC_USB3_AWIDTH bits of GHWPARAMS0 which
> > used for the DMA address width, and only configure 64-bit DMA
> > mask if the DWC_USB3_AWIDTH is 64.
> >
> > Fixes: 45d39448b4d0 ("usb: dwc3: support 64 bit DMA in platform driver")
> > Signed-off-by: William Wu <william.wu@xxxxxxxxxxxxxx>
>
> Reviewed-by: Sven Peter <sven@xxxxxxxxxxxxx>
>
> > ---
> >   drivers/usb/dwc3/core.c | 13 +++++++------
> >   1 file changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index c5c238ab3083..2fcbd05b2af1 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1751,12 +1751,6 @@ static int dwc3_probe(struct platform_device *pdev)
> >
> >   	dwc3_get_properties(dwc);
> >
> > -	if (!dwc->sysdev_is_parent) {
> > -		ret = dma_set_mask_and_coherent(dwc->sysdev, DMA_BIT_MASK(64));
> > -		if (ret)
> > -			return ret;
> > -	}
> > -
> >   	dwc->reset = devm_reset_control_array_get_optional_shared(dev);
> >   	if (IS_ERR(dwc->reset))
> >   		return PTR_ERR(dwc->reset);
> > @@ -1823,6 +1817,13 @@ static int dwc3_probe(struct platform_device
> > *pdev)
> >   	dwc3_cache_hwparams(dwc);
> >   	device_init_wakeup(&pdev->dev, of_property_read_bool(dev->of_node,
> > "wakeup-source"));
> >
> > +	if (!dwc->sysdev_is_parent &&
> > +	    DWC3_GHWPARAMS0_AWIDTH(dwc->hwparams.hwparams0) == 64) {
> > +		ret = dma_set_mask_and_coherent(dwc->sysdev, DMA_BIT_MASK(64));
> > +		if (ret)
> > +			goto disable_clks;
> > +	}
>
> I guess you could also create the mask from DWC3_GHWPARAMS0_AWIDTH(dwc->hwparams.hwparams0)
> directly instead of hardcoding it to 64bit here. Probably doesn't matter though unless
> there are some weird systems where dwc3 can only do 48bit DMA but there's actually memory
> above that.
Refer to the DWC3 databook "Table 4-1 Basic Config Parameters", it 
describe that "If your system address bus width for example is 40bits, 
select 64 and tie the address bits[63:40] of the DWC3_usb3 to 0", so it 
seems that "DWC3_GHWPARAMS0_AWIDTH(dwc->hwparams.hwparams0) == 64" can 
cover 40-bit DMA or 48-bit DMA.