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SubjectRe: [PATCH] usb: dwc3: core: leave default DMA if the controller does not support 64-bit DMA
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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@rock-chips.com>
>
> Reviewed-by: Sven Peter <sven@svenpeter.dev>
>
>> ---
>> 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.

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