Re: [PATCH 2/2] usb-storage: revert from scsi_add_host_with_dma() to scsi_add_host()

[Tom Yan <tom.ty89@gmail.com>]

It's merely a moving of comment moving for/and a no-behavioral-change
adaptation for the reversion. Similar has been done in the equivalent
patch for the UAS driver (and the reason is stated there).

On Mon, 30 Nov 2020 at 17:50, Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi,
>
> On 11/28/20 4:48 PM, Tom Yan wrote:
> > While the change only seemed to have caused issue on uas drives, we
> > probably want to avoid it in the usb-storage driver as well, until
> > we are sure it is the right thing to do.
> >
> > Signed-off-by: Tom Yan <tom.ty89@gmail.com>
>
> This seems to do a whole lot more then just dropping back from
>  scsi_add_host_with_dma() to scsi_add_host(). This has way more
> lines then the orginal commit.
>
> IMHO it would be best to just revert commit 0154012f8018bba4d9971d1007c12ffd48539ddb
> and then submit these changes as a separate patch (which would be
> 5.11 material then).
>
> That separate patch could then also have a proper commit message
> explaining the other changes you are making, which is also not
> unimportant.
>
> Regards,
>
> Hans
>
>
>
>
> > ---
> >  drivers/usb/storage/scsiglue.c | 40 +++++++++++++++++-----------------
> >  drivers/usb/storage/usb.c      |  3 +--
> >  2 files changed, 21 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
> > index 560efd1479ba..6539bae1c188 100644
> > --- a/drivers/usb/storage/scsiglue.c
> > +++ b/drivers/usb/storage/scsiglue.c
> > @@ -92,7 +92,7 @@ static int slave_alloc (struct scsi_device *sdev)
> >  static int slave_configure(struct scsi_device *sdev)
> >  {
> >       struct us_data *us = host_to_us(sdev->host);
> > -     struct device *dev = sdev->host->dma_dev;
> > +     struct device *dev = us->pusb_dev->bus->sysdev;
> >
> >       /*
> >        * Many devices have trouble transferring more than 32KB at a time,
> > @@ -120,6 +120,25 @@ static int slave_configure(struct scsi_device *sdev)
> >                * better throughput on most devices.
> >                */
> >               blk_queue_max_hw_sectors(sdev->request_queue, 2048);
> > +     } else {
> > +             /*
> > +              * Limit the total size of a transfer to 120 KB.
> > +              *
> > +              * Some devices are known to choke with anything larger. It seems like
> > +              * the problem stems from the fact that original IDE controllers had
> > +              * only an 8-bit register to hold the number of sectors in one transfer
> > +              * and even those couldn't handle a full 256 sectors.
> > +              *
> > +              * Because we want to make sure we interoperate with as many devices as
> > +              * possible, we will maintain a 240 sector transfer size limit for USB
> > +              * Mass Storage devices.
> > +              *
> > +              * Tests show that other operating have similar limits with Microsoft
> > +              * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
> > +              * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
> > +              * and 2048 for USB3 devices.
> > +              */
> > +             blk_queue_max_hw_sectors(sdev->request_queue, 240);
> >       }
> >
> >       /*
> > @@ -627,25 +646,6 @@ static const struct scsi_host_template usb_stor_host_template = {
> >       .sg_tablesize =                 SG_MAX_SEGMENTS,
> >
> >
> > -     /*
> > -      * Limit the total size of a transfer to 120 KB.
> > -      *
> > -      * Some devices are known to choke with anything larger. It seems like
> > -      * the problem stems from the fact that original IDE controllers had
> > -      * only an 8-bit register to hold the number of sectors in one transfer
> > -      * and even those couldn't handle a full 256 sectors.
> > -      *
> > -      * Because we want to make sure we interoperate with as many devices as
> > -      * possible, we will maintain a 240 sector transfer size limit for USB
> > -      * Mass Storage devices.
> > -      *
> > -      * Tests show that other operating have similar limits with Microsoft
> > -      * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
> > -      * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
> > -      * and 2048 for USB3 devices.
> > -      */
> > -     .max_sectors =                  240,
> > -
> >       /* emulated HBA */
> >       .emulated =                     1,
> >
> > diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
> > index c2ef367cf257..f177da4ff1bc 100644
> > --- a/drivers/usb/storage/usb.c
> > +++ b/drivers/usb/storage/usb.c
> > @@ -1050,8 +1050,7 @@ int usb_stor_probe2(struct us_data *us)
> >       usb_autopm_get_interface_no_resume(us->pusb_intf);
> >       snprintf(us->scsi_name, sizeof(us->scsi_name), "usb-storage %s",
> >                                       dev_name(dev));
> > -     result = scsi_add_host_with_dma(us_to_host(us), dev,
> > -                                     us->pusb_dev->bus->sysdev);
> > +     result = scsi_add_host(us_to_host(us), dev);
> >       if (result) {
> >               dev_warn(dev,
> >                               "Unable to add the scsi host\n");
> >
>