On Mon, Dec 06, 2010 at 03:28:23PM +0100, Joerg Hohwieler wrote: > Please cc me as I'm not subscribed ... > > > I have some issues with the Pyramid USB LCD display which is equipped > with an ftdi_chip. > > The relevant dmesg output: > usb 5-2: new full speed USB device using ohci_hcd and address 3 > usb 5-2: New USB device found, idVendor=0403, idProduct=e6c8 > usb 5-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0 > usb 5-2: Product: KBS USB LCD Display > usb 5-2: Manufacturer: KBS > usbcore: registered new interface driver usbserial > USB Serial support registered for generic > usbcore: registered new interface driver usbserial_generic > usbserial: USB Serial Driver core > USB Serial support registered for FTDI USB Serial Device > ftdi_sio 5-2:1.0: FTDI USB Serial Device converter detected > usb 5-2: Detected FT232BM > usb 5-2: Number of endpoints 2 > usb 5-2: Endpoint 1 MaxPacketSize 64 > usb 5-2: Endpoint 2 MaxPacketSize 64 > usb 5-2: Setting MaxPacketSize 64 > usb 5-2: FTDI USB Serial Device converter now attached to ttyUSB0 > usbcore: registered new interface driver ftdi_sio > ftdi_sio: v1.6.0:USB FTDI Serial Converters Driver > > > With recent kernels the display text ouput is very slow and it seems to > be some kind of luck if the server screen of lcdproc comes up. Even > recognition of keypress is delayed. > > The workaround I've found is: > > - make sure CONFIG_HZ is <= 250 > - disable highres timers > > > While using highres=off on kernel command line is quite easy, it's very > problematic to force users to build a new kernel if CONFIG_HZ is set to > 1000. > > And to me it seems that more and more distributions step forward using > CONFIG_HZ=1000. > > > I think the problem is somehow related to delayed interrupt handling of > the display driver. But I don't know where to look at. I think > ftdi_sio.c and usb-serial.c are involved. Do you see the data being sent to the device slowly across the serial part of the connection? It would be good for you to try to narrow down the part that causes the slowdowns, as you have a lot of different things combined all at once here. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
