Hi Christoph, I think we should continue to discuss on this email thread instead of the fixed DMA-API.txt patch [1]
[1] https://marc.info/?t=155989412200001&r=1&w=2 > From: Yoshihiro Shimoda, Sent: Monday, June 3, 2019 3:42 PM > > Hi linux-block and iommu mailing lists, > > I have an issue that a USB SSD with xHCI on R-Car H3 causes "swiotlb is full" > like below. > > [ 36.745286] xhci-hcd ee000000.usb: swiotlb buffer is full (sz: 524288 > bytes), total 32768 (slots), used 1338 (slots) > > I have investigated this issue by using git bisect, and then I found the > following commit: > > --- > commit 09324d32d2a0843e66652a087da6f77924358e62 > Author: Christoph Hellwig <h...@lst.de> > Date: Tue May 21 09:01:41 2019 +0200 > > block: force an unlimited segment size on queues with a virt boundary > --- Thank you for your comment on other email thread [2] like below: --- Turns out it isn't as simple as I thought, as there doesn't seem to be an easy way to get to the struct device used for DMA mapping from USB drivers. I'll need to think a bit more how to handle that best. --- [2] https://marc.info/?l=linux-doc&m=155989651620473&w=2 I'm not sure this is a correct way, but the issue disappears if I applied a patch below to USB storage driver. Especially, WARNING happened on blk_queue_max_segment_size(). Maybe we need to expand the argument "struct device *" of blk_queue_virt_boundary() to call dma_max_mapping_size()? --- diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c index 59190d8..fa37b39 100644 --- a/drivers/usb/storage/scsiglue.c +++ b/drivers/usb/storage/scsiglue.c @@ -28,6 +28,7 @@ * status of a command. */ +#include <linux/dma-mapping.h> #include <linux/module.h> #include <linux/mutex.h> @@ -83,6 +84,15 @@ static int slave_alloc (struct scsi_device *sdev) maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0); blk_queue_virt_boundary(sdev->request_queue, maxp - 1); +{ + struct device *dev = us->pusb_dev->bus->controller; + + dev_info(dev, "%s: size = %zu\n", __func__, dma_max_mapping_size(dev)); + blk_queue_max_segment_size(sdev->request_queue, + dma_max_mapping_size(dev)); +} + + /* * Some host controllers may have alignment requirements. * We'll play it safe by requiring 512-byte alignment always. --- Best regards, Yoshihiro Shimoda
