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backlight rework: Condat light driver accepts levels The present change is another intermediate step on the path toward new FreeCalypso backlight handling. At this intermediate step the Condat light driver accepts 0-255 backlight levels driven by MFW, and puts them out on PWL on Luna development boards. At the same time on C139 it is now possible to turn on the display backlight with or without the keypad bl - the lsb of the 0-255 backlight level controls the keypad bl. MFW presently drives only 0 and 255 backlight levels, thus there is no visible behavioral change yet - but the plan for subsequent stages of this backlight rework is to add a dimmed backlight state (no keypad bl on C139) during active calls.
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 24 Oct 2020 20:44:04 +0000
parents a1799f6d6aa7
children
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a1799f6d6aa7 doc/Nucleus-change article written
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1 The specific integration of ATI Nucleus PLUS RTOS in TI's stable TCS211 fw
a1799f6d6aa7 doc/Nucleus-change article written
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2 (which served as the baseline for several vendors' production fw) exhibits one
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3 hair-raising bug. While we don't know for sure where and how they maintained
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4 Nucleus library sources for compilation (the version we got has them censored
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5 out), we do see that Nucleus header files (nucleus.h and ??_defs.h) exist in
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6 two different locations in the source tree in two different versions:
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7
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8 * One version exists under chipsetsw/os/nucleus
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9 * The other version exists under gpf/inc/nuc & gpf/inc/nuc/arm7
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10
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11 The two versions of these header files under these two paths in TCS211 are not
a1799f6d6aa7 doc/Nucleus-change article written
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12 the same! The main nucleus.h header file is the same in both places, cs_defs.h
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13 and tm_defs.h versions differ only in comments, but tc_defs.h is the real
a1799f6d6aa7 doc/Nucleus-change article written
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14 kicker: the version under gpf/inc/nuc has an extra field added to the TC_HCB
a1799f6d6aa7 doc/Nucleus-change article written
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15 aka NU_HISR structure, making this structure one word longer than in the other
a1799f6d6aa7 doc/Nucleus-change article written
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16 version! More specifically, in ATI's original Nucleus this structure is 22
a1799f6d6aa7 doc/Nucleus-change article written
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17 words long with 4 unused dummy words at the end; TI's GPF version adds a fifth
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18 dummy word (thankfully toward the end, not shifting any actually-used members
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19 of the struct), putting the total struct size at 23 words.
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20
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21 It would be one thing if TI had made this change consistently, but they didn't:
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22 some modules were compiled with one version of the headers and got the 22-word
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23 version of the struct, while other modules were compiled with the other header
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24 file version and got the 23-word version of the struct. How can their fw work
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25 with this bug in it? Answer: TCS211 fw works despite this Nucleus integration
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26 bug because:
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28 * None of the actually-used members of the struct change offsets between the
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29 two versions;
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31 * Some places in the code have 22-word structs allocated in memory while other
a1799f6d6aa7 doc/Nucleus-change article written
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32 places have 23-word structs, but when they pass pointers to these structs to
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33 Nucleus API functions, those functions don't access past the actually-used
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34 part at the beginning (the part before dummy words), and they never do
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35 anything like zeroing out the full size of the expected struct.
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36
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37 * The only place in TCS211 fw where the total size of the struct matters is
a1799f6d6aa7 doc/Nucleus-change article written
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38 where NU_HISR is embedded in another structure, and there is one such place
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39 in GPF. Here breakage would result if different modules using these structs
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40 and arrays were compiled with different header file versions, but all modules
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41 that touch this part are compiled with the GPF version of nucleus.h, NU_DEBUG
a1799f6d6aa7 doc/Nucleus-change article written
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42 and tc_defs.h.
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43
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44 Needless to say, resolving this bogosity has been an important part of
a1799f6d6aa7 doc/Nucleus-change article written
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45 FreeCalypso firmware deblobbing. Naturally the most ideal solution would have
a1799f6d6aa7 doc/Nucleus-change article written
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46 been to remove the bogus extra word added by TI and consistently use the
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47 original 22-word struct everywhere, but there is one further complication: I
a1799f6d6aa7 doc/Nucleus-change article written
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48 (Mother Mychaela) don't feel comfortable with moving away from the original blob
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49 version of the OSL component of GPF, and these COFF objects have been compiled
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50 with the 23-word version of TC_HCB aka NU_HISR.
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51
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52 The following alternative approach has been implemented in FC Tourmaline:
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53
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54 * The new source version of Nucleus by Comrade XVilka has been checked in under
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55 src/nucleus, and this new source version is the one we are using instead of
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56 TI's binary object version.
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57
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58 * The new Nucleus header files src/nucleus/nucleus.h and src/nucleus/??_defs.h
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59 are the only ones used in Tourmaline - both old versions have been removed
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60 from active -I include paths.
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61
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62 * The new src/nucleus/tc_defs.h header file has been patched to replicate TI's
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63 23-word version of TC_HCB aka NU_HISR, and the NU_HISR_SIZE definition in
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64 src/nucleus/nucleus.h has also been adjusted to match.
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65
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66 Thus we are using the 23-word version of TC_HCB aka NU_HISR everywhere, with 5
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67 dummy words at the end rather than 4, adding 4 extra bytes of wasted RAM space
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68 to every instance of this struct throughout the firmware - but there are only a
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69 small number of these instances, thus the waste is negligible. In return we
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70 gain 100% consistency (the same version of the struct is used everywhere in our
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71 fw), and we retain the ability to keep the original OSL blobs which I am not
a1799f6d6aa7 doc/Nucleus-change article written
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72 ready to give up.