Date: Mon, 13 Jan 2020 15:52:17 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Wojciech Puchar <wojtek@puchar.net> Cc: freebsd-hackers@freebsd.org Subject: Re: raspberry pi zero and SLOW USB HID Message-ID: <9a1a3901-ce03-d445-dd9e-bbd775f5288a@selasky.org> In-Reply-To: <alpine.BSF.2.20.2001131539550.36878@puchar.net> References: <alpine.BSF.2.20.2001131439440.2189@puchar.net> <9f8ae63f-abe5-27d9-e6bf-3d0cc1d3d4f3@selasky.org> <alpine.BSF.2.20.2001131539550.36878@puchar.net>
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On 2020-01-13 15:44, Wojciech Puchar wrote: >> >> Can you check the USB speed used between PC and RPI-zero ? Is one >> perhaps High-Speed, while the other is, Full-Speed? >> >> If yes, try to connect a high-speed USB hub in between. >> >> Output from: >> usbconfig >> >> >> You can also check using "usbdump -i usbus0 -s 65536" to see the >> actual timing of the commands. >> Hi, I think I understand now. > device is the same hardware with the same firmware. What causes larger > delays? What you see is likely a manifestion of: #define DWC_OTG_HOST_TIMER_RATE 10 /* ms */ Which is because we want save a little power polling the DWC OTG. To avoid this: USB transfers must be double buffered! That means you must submit two IN-endpoint jobs, instead of just one. Then the driver will understand there is more work to do, and not go to idlewait! --HPS
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