[U-Boot] [PATCH v2 5/7] usb: dwc2-otg: fix warnings for ep->dma_buf for LP64 builds

[Dr. Philipp Tomsich]

Marek,

> On 06 Jun 2017, at 16:35, Marek Vasut <marex at denx.de> wrote:
> 
> On 06/06/2017 03:42 PM, Philipp Tomsich wrote:
>> For LP64 build w/ GCC 6.3, the handling of the ep->dma_buf variable
>> when (truncating and) writing into the controller's registers is
>> unsafe and triggers the following compiler warning (thus failing by
>> buildman tests):
>>  ../drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c: In function 'setdma_rx':
>>  ../drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c:116:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>>    writel((unsigned int) ep->dma_buf, &reg->out_endp[ep_num].doepdma);
>>           ^
>> 
>> This change fixes the warning and makes the code a bit more robust by
>> doing the following:
>> - we check whether ep->dma_buf can be safely truncated to 32 bits
>>  (i.e. whether dma_buf is the same value when masked to 32 bits) and
>>  emit an error message if that is not the case
>> - we cast to a uintptr_t and let the writel macro truncate the
>>  uintptr_t (potentially a 64bit value) to 32bits
>> 
>> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
>> 
>> ---
>> 
>> Changes in v2:
>> - (new patch) fix warnings and add some robustness for the truncation
>>  of ep->dma_buf in dwc2-otg for LP64 builds to fix a buildman failure
>>  for u-boot-rockchip/master at 2b19b2f
>> 
>> drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c b/drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c
>> index 0d6d2fb..f5c926c 100644
>> --- a/drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c
>> +++ b/drivers/usb/gadget/dwc2_udc_otg_xfer_dma.c
>> @@ -113,7 +113,11 @@ static int setdma_rx(struct dwc2_ep *ep, struct dwc2_request *req)
>> 	invalidate_dcache_range((unsigned long) ep->dma_buf,
>> 				(unsigned long) ep->dma_buf + ep->len);
>> 
>> -	writel((unsigned int) ep->dma_buf, &reg->out_endp[ep_num].doepdma);
>> +	/* ensure that ep->dma_buf fits into 32 bits */
>> +	if (((uintptr_t)ep->dma_buf & 0xffffffff) != (uintptr_t)ep->dma_buf)
>> +		error("ep->dma_buf does not fit into a 32 bits");
> 
> You print an error, but still continue with the function ? That'll
> probably lead to a crash, you should rather abort. In fact, I suspect
> you can use bounce-buffer to assure the dma buffer is in 32bit space.

This tries to stay close to the current behaviour (we have no hardware to test this,
but I wanted to get it out of the way as it caused buildman-failures) and to provide
diagnostics for whoever first encounters an issue here.

Note that I would only expect a DMA error, if someone really hit this issue ...

Regards,
Philipp.

>> +	writel((uintptr_t)ep->dma_buf, &reg->out_endp[ep_num].doepdma);
>> 	writel(DOEPT_SIZ_PKT_CNT(pktcnt) | DOEPT_SIZ_XFER_SIZE(length),
>> 	       &reg->out_endp[ep_num].doeptsiz);
>> 	writel(DEPCTL_EPENA|DEPCTL_CNAK|ctrl, &reg->out_endp[ep_num].doepctl);
>> 
> 
> 
> -- 
> Best regards,
> Marek Vasut