Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) ====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) Kernel driver ds2490
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) ====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) Supported chips:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7)   * Maxim DS2490 based
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) Description
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) -----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) The Maxim/Dallas Semiconductor DS2490 is a chip
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) which allows to build USB <-> W1 bridges.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) DS9490(R) is a USB <-> W1 bus master device
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) which has 0x81 family ID integrated chip and DS2490
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) low-level operational chip.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) Notes and limitations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) - The weak pullup current is a minimum of 0.9mA and maximum of 6.0mA.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) - The 5V strong pullup is supported with a minimum of 5.9mA and a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26)   maximum of 30.4 mA.  (From DS2490.pdf)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) - The hardware will detect when devices are attached to the bus on the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)   next bus (reset?) operation, however only a message is printed as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29)   the core w1 code doesn't make use of the information.  Connecting
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)   one device tends to give multiple new device notifications.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) - The number of USB bus transactions could be reduced if w1_reset_send
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)   was added to the API.  The name is just a suggestion.  It would take
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)   a write buffer and a read buffer (along with sizes) as arguments.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34)   The ds2490 block I/O command supports reset, write buffer, read
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35)   buffer, and strong pullup all in one command, instead of the current
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36)   1 reset bus, 2 write the match rom command and slave rom id, 3 block
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)   write and read data.  The write buffer needs to have the match rom
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)   command and slave rom id prepended to the front of the requested
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)   write buffer, both of which are known to the driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) - The hardware supports normal, flexible, and overdrive bus
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)   communication speeds, but only the normal is supported.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) - The registered w1_bus_master functions don't define error
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43)   conditions.  If a bus search is in progress and the ds2490 is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44)   removed it can produce a good amount of error output before the bus
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45)   search finishes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) - The hardware supports detecting some error conditions, such as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47)   short, alarming presence on reset, and no presence on reset, but the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)   driver doesn't query those values.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) - The ds2490 specification doesn't cover short bulk in reads in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)   detail, but my observation is if fewer bytes are requested than are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51)   available, the bulk read will return an error and the hardware will
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)   clear the entire bulk in buffer.  It would be possible to read the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53)   maximum buffer size to not run into this error condition, only extra
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54)   bytes in the buffer is a logic error in the driver.  The code should
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)   should match reads and writes as well as data sizes.  Reads and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56)   writes are serialized and the status verifies that the chip is idle
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)   (and data is available) before the read is executed, so it should
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)   not happen.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) - Running x86_64 2.6.24 UHCI under qemu 0.9.0 under x86_64 2.6.22-rc6
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)   with a OHCI controller, ds2490 running in the guest would operate
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61)   normally the first time the module was loaded after qemu attached
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)   the ds2490 hardware, but if the module was unloaded, then reloaded
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)   most of the time one of the bulk out or in, and usually the bulk in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64)   would fail.  qemu sets a 50ms timeout and the bulk in would timeout
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65)   even when the status shows data available.  A bulk out write would
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)   show a successful completion, but the ds2490 status register would
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67)   show 0 bytes written.  Detaching qemu from the ds2490 hardware and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68)   reattaching would clear the problem.  usbmon output in the guest and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)   host did not explain the problem.  My guess is a bug in either qemu
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70)   or the host OS and more likely the host OS.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) 03-06-2008 David Fries <David@Fries.net>