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  9. <title>EHCI debugging on the BeagleBone Black</title>
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  12. <div class="section">
  13. <h1 id="pagetop">EHCI debugging on the BeagleBone Black</h1>
  14. <p><a href="index.html">Back to previous index</a></p>
  15. </div>
  16. <div class="section">
  17. <h1>EHCI debugging</h1>
  18. <ol class="toc">
  19. <li><a href="#FindUSBportonthetargetthatsupportsEHCIdebug">Find
  20. USB port on the target that supports EHCI debug</a></li>
  21. <li><a href="#InitialsetupofBBBtoactasEHCIdebugdongle">Initial
  22. setup of BBB to act as EHCI debug dongle</a></li>
  23. <li><a href="#PatchBBBsgdbgpmoduleoptionalbuthighlyrecommended">Patch
  24. BBB's <tt>g_dbgp</tt> module (optional, but highly recommended)</a></li>
  25. <li><a href="#ConfigurelibrebootwithEHCIdebug">Configure
  26. libreboot with EHCI debug</a>
  27. <ol>
  28. <li><a href="#SelectingHCDIndexandUSBDebugport">Selecting
  29. <tt>HCD Index</tt> and <tt>USB Debug port</tt></a></li>
  30. </ol></li>
  31. <li><a href="#Howtogetthedebuglogs">How to get the debug
  32. logs</a></li>
  33. <li><a
  34. href="#EnebleEHCIDebugonthetargetskerneloptionalrecommended">Eneble
  35. EHCI Debug on the target's kernel (optional, recommended)</a></li>
  36. <li><a href="#References">References</a></li>
  37. </ol>
  38. <p>If your computer does not boot after installing libreboot, it is
  39. very useful to get debug logs from it, from the payload (grub) and/or
  40. the kernel (if gets to there). All of them stream debug logs on the
  41. available serial (RS-232) by default. However, most of todays laptops
  42. lack RS-232 port. The other option is to stream the logs to USB EHCI
  43. debug port.</p>
  44. <p>This section explains step-by-step how to setup BBB as a
  45. &#8220;USB EHCI debug dongle&#8221; and configure libreboot and the
  46. linux kernel to stream logs to it (TODO: grub).</p>
  47. <p>I will refer to three computers:</p>
  48. <ul>
  49. <li><b>host</b> - this is the computer you use, have
  50. tools, compiler, Internet, etc</li>
  51. <li><b>BBB</b> - Beaglebone Black (rev. B or higher, i
  52. use rev. C)</li>
  53. <li><b>target</b> - the computer you are trying to
  54. install liberboot</li>
  55. </ul>
  56. <h3 id="FindUSBportonthetargetthatsupportsEHCIdebug">Find USB port
  57. on the target that supports EHCI debug</h3>
  58. <p>
  59. Not all USB controllers support EHCI debug (see: <a
  60. href="http://www.coreboot.org/EHCI_Debug_Port#Hardware_capability">EHCI
  61. Debug Port</a> ). Even more, if a USB controller supports EHCI debug, it
  62. is available only <b>on a single port</b> that might or might
  63. not be exposed externally.
  64. </p>
  65. <ul>
  66. <li>You need running OS (GNU/Linux) on your target for this step
  67. (If you&#8217;ve flashed libreboot and it does not boot, you have to
  68. flush back the stock bios)</li>
  69. <li>You need USB memory stick (the data on it will not be
  70. touched).</li>
  71. <li>The EHCI debugging can not be done through external hub, BBB
  72. must be connected directly to the debug port of the controller (so, no
  73. hubs)</li>
  74. </ul>
  75. <ul>
  76. <li>Download<sup class="footnote"><a href="#___fn1">1</a></sup> <a
  77. href="http://www.coreboot.org/pipermail/coreboot/attachments/20080909/ae11c291/attachment.sh">this</a>
  78. shell script.
  79. </li>
  80. </ul>
  81. <ol>
  82. <li>Plug the usb stick in the first available usb port</li>
  83. <li>Run the script, you will get output similar to following:</li>
  84. <pre>The following PCI devices support a USB debug port (says lspci): 0000:00:1a.0 0000:00:1d.0
  85. The following PCI devices support a USB debug port (says the kernel): 0000:00:1a.0 0000:00:1d.0
  86. *PCI device 0000:00:1a.0, USB bus 3, USB physical port 1*
  87. *PCI device 0000:00:1d.0, USB bus 4, USB physical port 2*
  88. Currently connected high-speed devices:
  89. /: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
  90. |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/8p, 480M
  91. |__ Port 7: Dev 14, If 0, Class=Hub, Driver=hub/4p, 480M
  92. |__ Port 1: Dev 15, If 0, Class=Hub, Driver=hub/4p, 480M
  93. |__ Port 3: Dev 17, If 0, Class=Hub, Driver=hub/2p, 480M
  94. |__ Port 4: Dev 18, If 0, Class=Hub, Driver=hub/4p, 480M
  95. /: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
  96. |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/6p, 480M
  97. /: *Bus 01*.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 480M
  98. |__ *Port 3: Dev 31, If 0, Class=Mass Storage, Driver=usb-storage, 480M*
  99. </pre>
  100. <li>The buses the support debug are Bus 3 (0000:00:1a.0) on Port 1
  101. and Bus 4 (0000:00:1d.0) on port 2. Your usb stick is plugged on Bus
  102. 1, Port 3</li>
  103. <li>Repeat the steps, plugging the USB stick in the next available
  104. port</li>
  105. <li>Go through all available ports and remember(write down) those
  106. for which bus/port of the usb stick matches one of the bus/port that
  107. support debug (bold).</li>
  108. </ol>
  109. <p>Remember (write down) for each port (external plug) you found
  110. that supports debug: <b>PCI device id, the bus id, the port number, and
  111. the physical location of the usb plug.</b></p>
  112. <p>If you do not find a match, you can not get debug over EHCI.
  113. Sorry.</p>
  114. <p id="___fn1" class="footnote">
  115. <sup>1</sup> The guys from coreboot were talking about including the
  116. script in coreboot distribution (check the status).
  117. </p>
  118. <h3 id="InitialsetupofBBBtoactasEHCIdebugdongle">Initial setup of
  119. BBB to act as EHCI debug dongle</h3>
  120. <p>BBB must be powered with a barrel power connector since the
  121. mini-B USB plug will be used for the EHCI debug stream. So you will
  122. need:</p>
  123. <ul>
  124. <li>power supply (5V, 2A(10W) is sufficient).</li>
  125. <li>an extra usb cable: A to mini-B</li>
  126. </ul>
  127. <p>
  128. (On BBB) The linux kernel includes module (g_dbgp that enables one of the usb ports on a computer to behave as EHCI
  129. debug dongle. Make sure you have this module available on your BBB
  130. (Debian 7.8 that comes with BBB should have it), if not, you should
  131. compile it yourself (see next section):
  132. </p>
  133. <pre>ls /lib/modules/3.8.13-bone70/kernel/drivers/usb/gadget/g_dbgp.ko</pre>
  134. <p>
  135. Unload all other
  136. g_*
  137. modules:
  138. </p>
  139. <pre># lsmod
  140. # rmmod g_multi
  141. ...
  142. </pre>
  143. <p>
  144. Then load
  145. g_dbgp
  146. :
  147. </p>
  148. <pre># modprobe g_dbgp
  149. # lsmod # should show that g_dbgp is loaded, and no other g_*
  150. </pre>
  151. <p>
  152. Plug the mini-B side of the USB cable in your BBB and the A side in
  153. your target. Then one of the usb devices on your target (with
  154. lsusb
  155. ) should be:
  156. </p>
  157. <pre>Bus 001 Device 024: ID 0525:c0de Netchip Technology, Inc.</pre>
  158. <p>If you see the device on the target, you are good to continue to
  159. the next step.</p>
  160. <h3 id="PatchBBBsgdbgpmoduleoptionalbuthighlyrecommended">
  161. Patch BBB&#8217;s
  162. g_dbgp
  163. module (optional, but highly recommended)
  164. </h3>
  165. <p>
  166. For the reasons why you need this, see: <a
  167. href="http://www.coreboot.org/EHCI_Gadget_Debug">EHCI Gadget Debug</a>.<br />Make
  168. sure that you have cross compiling environment for
  169. arm-linux-gnueabihf
  170. setup on your <em>host</em>.
  171. </p>
  172. <ul>
  173. <li>On BBB: uname -r - this will give you version
  174. number like 3.8.13-bone70 (I will refer to this as: $mav.$miv-$lv:
  175. where mav=3.8, miv=13, lv=bone70
  176. </li>
  177. <li>Get the BBB kernel ready on your host for cross-compiling:</li>
  178. </ul>
  179. <pre>$ cd $work_dir
  180. $ git clone https://github.com/beagleboard/kernel.git
  181. $ cd kernel
  182. $ git checkout $mav (see above)
  183. $ ./patch.sh
  184. $ wget http://arago-project.org/git/projects/?p=am33x-cm3.git\;a=blob_plain\;f=bin/am335x-pm-firmware.bin\;hb=HEAD -O kernel/firmware/am335x-pm-firmware.bin
  185. $ cp configs/beaglebone kernel/arch/arm/configs/beaglebone_defconfig
  186. </pre>
  187. <ul>
  188. <li>Download the patch from <a
  189. href="http://www.coreboot.org/images/8/88/Ehci-debug-gadget-patches.tar.gz">here</a></li>
  190. <li>tar -xf Ehci-debug-gadget-patches.tar.gz (will
  191. create dir: usbdebug-gadget)</li>
  192. <li>Note that there are two patches (patch_1 and patch_2) for each
  193. of the two different version of the kernel (3.8 and 3.10). I will use
  194. 3.8. (If using kernel 3.12 patch_1 is not needed)</li>
  195. <li>cd kernel (note that this is one more level: you
  196. should be in $work_dir/kernel/kernel)</li>
  197. <li>Apply the patches:</li>
  198. </ul>
  199. <pre>
  200. git apply ../usbdebug-gadget/v3.8-debug-gadget/0001-usb-dbgp-gadget-Fix-re-connecting-after-USB-disconne.patch
  201. git apply ../usbdebug-gadget/v3.8-debug-gadget/0002-usb-serial-gadget-no-TTY-hangup-on-USB-disconnect-WI.patch
  202. ;
  203. make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- beaglebone_defconfig -j4@
  204. </pre>
  205. <ul>
  206. <li>
  207. You should also apply the linux-libre <i>deblob</i> script to turn it into linux-libre
  208. (deletes all the blobs from the linux kernel).
  209. <a href="http://www.fsfla.org/ikiwiki/selibre/linux-libre/">fsfla website</a>
  210. - see <a href="http://www.fsfla.org/svn/fsfla/software/linux-libre/scripts/">scripts</a>.
  211. </li>
  212. <li>Get your current BBB kernel config (from: /boot/config-&lt;ver&gt;)
  213. and copy it to your host as $work_dir/kernel/kernel/.config</li>
  214. <pre>
  215. make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- oldconfig - all default answers</pre>
  216. <li>Set proper version number:
  217. <ul>
  218. <li>On your host, edit $work_dir/kernel/kernel/.config
  219. (the one you&#8217;ve just copied from BBB), find the line CONFIG_LOCALVERSION="&lt;something
  220. or empty&gt;" and change it to CONFIG_LOCALVERSION="-$lv",
  221. so it will look something like: CONFIG_LOCALVERSION="-bone70"</li>
  222. </ul>
  223. </li>
  224. <li>Also, make sure that: CONFIG_USB_G_DBGP=m (If
  225. not, make menuconfig, and set @Device Drivers-&gt; USB
  226. Support -&gt; USB Gadget Support -&gt; EHCI Debug Device Gadget=m</li>
  227. <li>Build the module:</li>
  228. </ul>
  229. <pre>
  230. $ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j4 (is it possoble to build only the gadget modules)
  231. $ mkdir ../tmp &amp;&amp; make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- INSTALL_MOD_PATH=../tmp modules_install
  232. </pre>
  233. <ul>
  234. <li>on BBB, backup /lib/modules/3.8.13-bone70/kernel/drivers/usb/gadget
  235. (i.e. mv
  236. /lib/modules/3.8.13-bone70/kernel/drivers/usb/gadget $HOME)
  237. </li>
  238. <li>copy the freshly compiled usb/gadget dir to /lib/modules/3.8.13-bone70/kernel/drivers/usb</li>
  239. <li>restart BBB</li>
  240. <li>Remove all g_* modules (rmmod
  241. g_&lt;&gt;)
  242. </li>
  243. <li>modprobpe g_dbgp</li>
  244. </ul>
  245. <h3 id="ConfigurelibrebootwithEHCIdebug">Configure libreboot with
  246. EHCI debug</h3>
  247. <p>
  248. Libreboot(coreboot) should be configured with debug turned on and to
  249. push debug messages to the EHCI debug port.<br />If you&#8217;ve
  250. downloaded the binary distribution, you can check if it is properly
  251. configured in the following way:
  252. </p>
  253. <ul>
  254. <li>Go to the libreboot dist root directory cd
  255. $libreboot_bin</li>
  256. <li>Locate the rom image for your target (I will call it: $img_path)
  257. </li>
  258. <li>Running the following command will extract the config in a
  259. file ./my_config:
  260. </li>
  261. </ul>
  262. <pre>
  263. ./cbfstool/i686/cbfstool $img_path extract -n config -f ./my_config
  264. </pre>
  265. <ul>
  266. <li>Make sure that the following params in the config are set as
  267. following:</li>
  268. </ul>
  269. <pre>
  270. CONFIG_USBDEBUG=y (Generic Drivers -&gt; USB 2.0 EHCI debug dongle support)
  271. CONFIG_USBDEBUG_IN_ROMSTAGE=y (Generic Drivers -&gt; Enable early (pre-RAM) usbdebug)
  272. CONFIG_USBDEBUG_HCD_INDEX=&lt;HCD Index of usb controller - see below&gt; (Generic Drivers -&gt; Index for EHCI controller to use with usbdebug)
  273. CONFIG_USBDEBUG_DEFAULT_PORT=&lt;USB Debug port - see below&gt; (Generic Drivers -&gt; Default USB port to use as Debug Port)
  274. </pre>
  275. <p>
  276. The following three are behind radio button in the menu. Only the first
  277. one<sup class="footnote"><a href="#___fn2">2</a></sup> should be = y
  278. </p>
  279. <pre>
  280. USBDEBUG_DONGLE_STD=y (Generic Drivers -&gt; Type of dongle (Net20DC or compatible) -&gt; Net20DC or compatible)
  281. CONFIG_USBDEBUG_DONGLE_BEAGLEBONE=n (Generic Drivers -&gt; Type of dongle (Net20DC or compatible) -&gt; BeagleBone)
  282. CONFIG_USBDEBUG_DONGLE_BEAGLEBONE_BLACK=n (Generic Drivers -&gt; Type of dongle (Net20DC or compatible) -&gt; BeagleBone Black)
  283. </pre>
  284. <p id="___fn2" class="footnote">
  285. <sup>2</sup> The g_dbgp module on BeagleBone Black (Rev. C) reports it self as Net20DC, the
  286. other options are for older BB(B) - ver1. This is documented <a
  287. href="https://johnlewis.ie/coreboot-ehci-debug-gadget-demonstration/">here</a>
  288. (also tested/verified).
  289. </p>
  290. <p>
  291. Then:<br />
  292. <pre>
  293. CONFIG_CONSOLE_USB=y (Console -&gt; USB dongle console output)
  294. </pre>
  295. </p>
  296. <p>
  297. Also
  298. Debugging ---&gt; Output verbose XYZ
  299. ) (<b>FIXME</b> somebody verify these):
  300. </p>
  301. <pre>
  302. CONFIG_DEBUG_CBFS=y (Output verbose CBFS debug messages )
  303. CONFIG_HAVE_DEBUG_RAM_SETUP=y (??? What/where is this)
  304. CONFIG_DEBUG_RAM_SETUP=y (Output verbose RAM init debug messages)
  305. CONFIG_DEBUG_SMI=y (Output verbose SMI debug messages)
  306. CONFIG_DEBUG_ACPI=y (Output verbose ACPI debug messages )
  307. CONFIG_DEBUG_USBDEBUG=y (Output verbose USB 2.0 EHCI debug dongle messages)
  308. </pre>
  309. <p>If some of the above mentioned configuration options are not as
  310. specified, you have to configure and compile libreboot yourself. Please
  311. refer to the doc(<b>FIXME: link</b> about compiling libreboot.</p>
  312. <h4 id="SelectingHCDIndexandUSBDebugport">
  313. Selecting
  314. HCD Index
  315. and
  316. USB Debug port
  317. </h4>
  318. <p>
  319. This applies (and works) only if the USB controller that supports debug
  320. (found in the first section) is from Intel.<br />If the PCI ID of the
  321. port you found in the first section is
  322. 0000:00:1a.0
  323. or
  324. 0000:00:1d.0
  325. , you are ok. Otherwise you have to try without guarantee that will
  326. work.
  327. </p>
  328. <p>
  329. If the externally exposed port is on a bus with
  330. PCI ID == 0000:00:1a.0
  331. then for
  332. CONFIG_USBDEBUG_HCD_INDEX
  333. choose 2, otherwise choose 0
  334. .
  335. </p>
  336. <p>
  337. For
  338. CONFIG_USBDEBUG_DEFAULT_PORT
  339. choose the port from the first section that correspond to the
  340. PCI ID
  341. </p>
  342. <p>
  343. Notes:<br />The above is based on the implementation of
  344. coreboot/src/southbridge/intel/common/usb_debug.c : pci_ehci_dbg_dev()
  345. .<br />This is enough as it applies for the supported GM45/G45
  346. Thinkpads. coreboot support some other contollers too, but they are
  347. irellevent for libreboot (for now).
  348. </p>
  349. <ul>
  350. <li>On T500 (with switchable GPU) the debug ports for both intel
  351. controllers is exposed.</li>
  352. <li>On x200t the debug ports for both intel controllers is
  353. exposed.</li>
  354. </ul>
  355. <h3 id="Howtogetthedebuglogs">How to get the debug logs</h3>
  356. <ul>
  357. <li>Plug the USB cable in the target&#8217;s debug port (the one
  358. you found in step 1) and BBB&#8217;s mini-B USB</li>
  359. <li>Make sure no other then g_dbgp of the g_*
  360. modules is loaded on your BBB
  361. </li>
  362. <li>On the BBB:</li>
  363. </ul>
  364. <pre>
  365. stty -icrnl -inlcr -F /dev/ttyGS0
  366. cat /dev/ttyGS0
  367. </pre>
  368. <ul>
  369. <li>Power on the target with libreboot</li>
  370. <li>You should see debug logs comming on your BBB console</li>
  371. </ul>
  372. <p>
  373. Note that this is not permanent on BBB, if you reboot it, you have to
  374. rmmod g_*
  375. and
  376. modprobe g_dbgp
  377. </p>
  378. <h3 id="EnebleEHCIDebugonthetargetskerneloptionalrecommended">Eneble
  379. EHCI Debug on the target&#8217;s kernel (optional, recommended)</h3>
  380. <p>You have to know how to compile kernel for your target.</p>
  381. <ol>
  382. <li>Check if early debugging is already enabled: grep
  383. CONFIG_EARLY_PRINTK_DBGP /boot/config-&lt;ver&gt;</li>
  384. <li>If enabled, you do not have to compile the kernel (skip this
  385. step). Otherwise, prepare kernel source for your distribution and
  386. select (Kernel hacking -&gt; Early printk via EHCI debug
  387. port). Compile and install the new kernel.
  388. </li>
  389. <li>Edit your grub configuration and add following to the kenel
  390. parameters<sup class="footnote"><a href="#___fn20">20</a></sup><sup
  391. class="footnote"><a href="#___fn21">21</a></sup>: earlyprintk=dbgp,keep.
  392. Also, try: earlyprintk=dbgp&lt;N&gt;,keep where N
  393. is the debug port id if the first does not work.
  394. </li>
  395. </ol>
  396. <h3 id="References">References</h3>
  397. <p id="___fn10" class="footnote">
  398. <sup>10</sup> <a href="http://www.coreboot.org/EHCI_Debug_Port">EHCI
  399. Debug Port</a>
  400. </p>
  401. <p id="___fn11" class="footnote">
  402. <sup>11</sup> <a
  403. href="https://johnlewis.ie/coreboot-ehci-debug-gadget-demonstration/">coreboot
  404. EHCI debug gadget demonstration</a>
  405. </p>
  406. <p id="___fn12" class="footnote">
  407. <sup>12</sup> <a href="http://www.coreboot.org/EHCI_Gadget_Debug">EHCI
  408. Gadget Debug</a>
  409. </p>
  410. <p id="___fn13" class="footnote">
  411. <sup>13</sup> <a
  412. href="http://www.coreboot.org/images/8/88/Ehci-debug-gadget-patches.tar.gz">Ehci-debug-gadget-patches.tar.gz</a>
  413. </p>
  414. <p id="___fn14" class="footnote">
  415. <sup>14</sup> <a
  416. href="http://wiki.beyondlogic.org/index.php/BeagleBoneBlack_Building_Kernel">Compiling
  417. the BeagleBone Black Kernel</a>
  418. </p>
  419. <p id="___fn15" class="footnote">
  420. <sup>15</sup>
  421. http://dumb-looks-free.blogspot.ca/2014/06/beaglebone-black-bbb-compile-kernel.html
  422. </p>
  423. <p id="___fn16" class="footnote">
  424. <sup>16</sup>
  425. http://dumb-looks-free.blogspot.fr/2014/06/beaglebone-black-bbb-kernal-headers.html
  426. </p>
  427. <p id="___fn17" class="footnote">
  428. <sup>17</sup> <a href="http://elinux.org/Building_BBB_Kernel">Building
  429. BBB Kernel</a>
  430. </p>
  431. <p id="___fn18" class="footnote">
  432. <sup>18</sup>
  433. http://komposter.com.ua/documents/USB-2.0-Debug-Port%28John-Keys%29.pdf
  434. </p>
  435. <p id="___fn19" class="footnote">
  436. <sup>19</sup> <a href="http://cs.usfca.edu/~cruse/cs698s10/">Exploring
  437. USB at the Hardware/Software Interface</a>
  438. </p>
  439. <p id="___fn20" class="footnote">
  440. <sup>20</sup>
  441. https://www.kernel.org/doc/Documentation/x86/earlyprintk.txt
  442. </p>
  443. <p id="___fn21" class="footnote">
  444. <sup>21</sup> https://wiki.ubuntu.com/Kernel/Debugging/USBearlyprintk
  445. </p>
  446. <p>
  447. <b>TODO</b>:
  448. </p>
  449. <ol>
  450. <li>grub does not send messages to EHCI debug. Investigate.</li>
  451. <li>The section &#8220;Configure libreboot with EHCI debug&#8221;
  452. can be skipped/simplified if a common configuration works for all
  453. relevant targets is selected as defualt</li>
  454. <li>Patch and compule g_dbgp on BBB instead cross-compile</li>
  455. <li>Find a simple way to send debug messages from targets userland</li>
  456. </ol>
  457. </div>
  458. <div class="section">
  459. <p>
  460. Copyright &copy; 2015 Alex David &lt;opdecirkel@gmail.com&gt;<br/>
  461. Permission is granted to copy, distribute and/or modify this document
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  463. or any later version published by the Free Software Foundation;
  464. with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
  465. A copy of the license can be found at <a href="../gfdl-1.3.txt">../gfdl-1.3.txt</a>
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