linux-kernel - [PATCH 1/2] uas: revert from scsi_add_host_with_dma() to scsi_add

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Message-Id: <20201128154849.3193-1-tom.ty89@gmail.com>
Date:   Sat, 28 Nov 2020 23:48:48 +0800
From:   Tom Yan <tom.ty89@...il.com>
To:     hdegoede@...hat.com, hch@....de, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org
Cc:     mathias.nyman@...el.com, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, baolu.lu@...ux.intel.com,
        Tom Yan <tom.ty89@...il.com>
Subject: [PATCH 1/2] uas: revert from scsi_add_host_with_dma() to scsi_add_host()

Apparently the former (with the chosen dma_dev) may cause problem in certain
case (e.g. where thunderbolt dock and intel iommu are involved). The error
observed was:

XHCI swiotlb buffer is full / DMAR: Device bounce map failed

For now we retain the clamp for hw_max_sectors against the dma_max_mapping_size.
Since the device/size for the clamp that is applied when the scsi request queue
is initialized/allocated is different than the one used here, we invalidate the
early clamping by making a fallback blk_queue_max_hw_sectors() call.

Signed-off-by: Tom Yan <tom.ty89@...il.com>
---
 drivers/usb/storage/uas.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index c8a577309e8f..5db1325cea20 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -843,18 +843,21 @@ static int uas_slave_alloc(struct scsi_device *sdev)
 static int uas_slave_configure(struct scsi_device *sdev)
 {
 	struct uas_dev_info *devinfo = sdev->hostdata;
-	struct device *dev = sdev->host->dma_dev;
+	struct usb_device *udev = devinfo->udev;
 
 	if (devinfo->flags & US_FL_MAX_SECTORS_64)
 		blk_queue_max_hw_sectors(sdev->request_queue, 64);
 	else if (devinfo->flags & US_FL_MAX_SECTORS_240)
 		blk_queue_max_hw_sectors(sdev->request_queue, 240);
-	else if (devinfo->udev->speed >= USB_SPEED_SUPER)
+	else if (udev->speed >= USB_SPEED_SUPER)
 		blk_queue_max_hw_sectors(sdev->request_queue, 2048);
+	else
+		blk_queue_max_hw_sectors(sdev->request_queue,
+					 SCSI_DEFAULT_MAX_SECTORS);
 
 	blk_queue_max_hw_sectors(sdev->request_queue,
 		min_t(size_t, queue_max_hw_sectors(sdev->request_queue),
-		      dma_max_mapping_size(dev) >> SECTOR_SHIFT));
+		      dma_max_mapping_size(udev->bus->sysdev) >> SECTOR_SHIFT));
 
 	if (devinfo->flags & US_FL_NO_REPORT_OPCODES)
 		sdev->no_report_opcodes = 1;
@@ -1040,7 +1043,7 @@ static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	shost->can_queue = devinfo->qdepth - 2;
 
 	usb_set_intfdata(intf, shost);
-	result = scsi_add_host_with_dma(shost, &intf->dev, udev->bus->sysdev);
+	result = scsi_add_host(shost, &intf->dev);
 	if (result)
 		goto free_streams;
 
-- 
2.29.2