On Tue, Aug 12, 2014 at 04:02:59PM +0200, Johan Hovold wrote: > On Sat, Aug 09, 2014 at 02:46:56AM +0800, Wang YanQing wrote: > > On Fri, Aug 08, 2014 at 09:54:42AM +0200, Johan Hovold wrote: > > > On Fri, Aug 08, 2014 at 03:10:34AM +0800, Wang YanQing wrote: > > > > On Tue, Aug 05, 2014 at 03:54:08PM +0200, Johan Hovold wrote: > > > > > > > I noticed that setting direction to output and setting the gpio > > > > > > > high has > > > > > > > no effect on the read-back value (i.e. I still read back 0) for my > > > > > > > pl2303hx (note that my device has no easily accessible gpios so I > > > > > > > haven't verified the actual state of the output pin). > > > > > > > > > > > > > > What happens on your system? Is the read-back value still 0, even > > > > > > > when > > > > > > > the GPIO output is actually high? Should we return the cached > > > > > > > value in > > > > > > > this case? > > > > > > > > > > > > If i set direction to output, then I could control gpio high and low > > > > > > by set 1 or 0, and the read-back value is 1 or 0 according to high > > > > > > and > > > > > > low(I test high and low by oscillscope) > > > > > > > > > > > > I test it with my pl2303hx with only two gpios. > > > > > > > > > > > > Could you use usbmon to see whether the traffic is right according > > > > > > to comment in struct pl2303_gpio? > > > > > > > > > > The traffic appears correct judging from the debug output (which I > > > > > trust). Output-enable is reflected in register 0x81, but the value > > > > > isn't. > > > > > > > > > > What is the lsusb -v output for your device? > > > > > > > > Bus 001 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 > > > > Serial Port. > > > > > > You forgot the verbose flag (-v). > > Sorry, below is output with -v: > > Bus 002 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial > > Port > > Device Descriptor: > > bLength 18 > > bDescriptorType 1 > > bcdUSB 1.10 > > bDeviceClass 0 (Defined at Interface level) > > bDeviceSubClass 0 > > bDeviceProtocol 0 > > bMaxPacketSize0 64 > > idVendor 0x067b Prolific Technology, Inc. > > idProduct 0x2303 PL2303 Serial Port > > bcdDevice 3.00 > > You seem to have an HX device, whereas mine is an HXD (rev D) with > bcdDevice 4.00. That could account for the different behaviour of the > GPIO state/value register. > > How did you figure out which registers to use? Were you sniffing the > traffic of some driver for some other OS? And does your device only have > two GPIOs and not four like the HX rev D?
After I found I need to use GPIOs in pl2303, I found below patch in Internet firstly: http://comments.gmane.org/gmane.linux.usb.general/65066 Then I verified the protocol by sniffing the traffic of some driver for some other OS running in virtualbox, and host OS is linux:) Prolific has pl2303 gpio test program (.exe) for windows, maybe you could find it from Internet. It support HXA and HXD, I use it to test two gpios in my pl2303HXA, and analyze output of usbmon. Yes, my device only have two GPIOs. > <snip> > > > > > It is strange your device doesn't work, I verify the control method by > > > > analyze usbmon output from linux host which has VirtualBox running > > > > gpio test program, but I don't have right to distribute the gpio test > > > > program I think, so I can't help you to figure out why it doesn't work > > > > for your device. > > > > > > What do you use the gpio test program for? I thought you verified the > > > gpios with a scope? > > > > Yes, I verified gpios with a scope. > > > > " > > You must allocate the buffer dynamically as some platforms cannot do > > DMA to the stack. > > " > > Thanks very much for point out it, could you clarify it? > > I want to know the reason. > > The memory where the stack resides might not be available for DMA, and > even if it is, there could still be problems with cache coherency. It is still vague: stack memory maybe resident higher place than normal memory, but I don't think kmalloc could be immune from this problem, unless we use GFP_DMA? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
