| Message ID | 1515110659-20145-4-git-send-email-brad@nextdimension.cc (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jan 4, 2018 at 7:04 PM, Brad Love <brad@nextdimension.cc> wrote: > Hauppauge em28xx bulk devices exhibit continuity errors and corrupted > packets, when run in VMWare virtual machines. Unknown if other > manufacturers bulk models exhibit the same issue. KVM/Qemu is unaffected. > > According to documentation the maximum packet multiplier for em28xx in bulk > transfer mode is 256 * 188 bytes. This changes the size of bulk transfers > to maximum supported value and have a bonus beneficial alignment. > > Before: > # 512 * 384 = 196608 > ## 196608 % 188 != 0 > > After: > # 512 * 47 * 2 = 48128 (188 * 128 * 2) > ## 48128 % 188 = 0 > > This sets up USB to expect just as many bytes as the em28xx is set to emit. > > Successful usage under load afterwards natively and in both VMWare > and KVM/Qemu virtual machines. > > Signed-off-by: Brad Love <brad@nextdimension.cc> :+1 Reviewed-by: Michael Ira Krufky <mkrufky@linuxtv.org> > --- > drivers/media/usb/em28xx/em28xx.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h > index c85292c..7be8ac9 100644 > --- a/drivers/media/usb/em28xx/em28xx.h > +++ b/drivers/media/usb/em28xx/em28xx.h > @@ -191,7 +191,7 @@ > USB 2.0 spec says bulk packet size is always 512 bytes > */ > #define EM28XX_BULK_PACKET_MULTIPLIER 384 > -#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 384 > +#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 94 > > #define EM28XX_INTERLACED_DEFAULT 1 > > -- > 2.7.4 >
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h index c85292c..7be8ac9 100644 --- a/drivers/media/usb/em28xx/em28xx.h +++ b/drivers/media/usb/em28xx/em28xx.h @@ -191,7 +191,7 @@ USB 2.0 spec says bulk packet size is always 512 bytes */ #define EM28XX_BULK_PACKET_MULTIPLIER 384 -#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 384 +#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 94 #define EM28XX_INTERLACED_DEFAULT 1
Hauppauge em28xx bulk devices exhibit continuity errors and corrupted packets, when run in VMWare virtual machines. Unknown if other manufacturers bulk models exhibit the same issue. KVM/Qemu is unaffected. According to documentation the maximum packet multiplier for em28xx in bulk transfer mode is 256 * 188 bytes. This changes the size of bulk transfers to maximum supported value and have a bonus beneficial alignment. Before: # 512 * 384 = 196608 ## 196608 % 188 != 0 After: # 512 * 47 * 2 = 48128 (188 * 128 * 2) ## 48128 % 188 = 0 This sets up USB to expect just as many bytes as the em28xx is set to emit. Successful usage under load afterwards natively and in both VMWare and KVM/Qemu virtual machines. Signed-off-by: Brad Love <brad@nextdimension.cc> --- drivers/media/usb/em28xx/em28xx.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)