DVDInterface: Translate and align offsets for timing purposes #1900

JosJuice · 2015-01-17T12:04:54Z

This is a fairly large timing change for decrypted reads and a smaller timing change for non-decrypted reads.

Source/Core/Core/HW/DVDInterface.cpp

@@ -1291,7 +1343,7 @@ u64 SimulateDiscReadTime(u64 offset, u32 length)
 		}
 	}

-	g_last_read_offset = (offset + length - 2048) & ~2047;
+	g_last_read_offset = end_offset;


JosJuice · 2015-01-17T21:09:10Z

I've added a fix for buffered decrypted reads. Not sure how good it is.

delroth · 2015-01-17T21:10:11Z

@dolphin-emu-bot rebuild (sorry, was doing some buildbot maintenance at the same time)

Buddybenj · 2015-03-16T13:08:52Z

Ping?

skidau · 2015-03-18T02:58:51Z

How did you test this? How did you tell that this is more accurate?

JosJuice · 2015-03-18T08:21:32Z

I don't have a good way to test this, really... :/ I guess it would be possible to compare the loading times in some Wii game, but if we want something less approximate, writing custom homebrew software would probably be needed. CleanRip won't help with this, because it doesn't decrypt and it reads everything using big, aligned requests. But while I don't know how accurate things are with this PR, I know that the old way of completely ignoring decryption can't be right. It would require the disc drive to magically read faster whenever IOS wants to decrypt data.

shuffle2 · 2015-05-08T02:00:33Z

It's hard to say if this is more accurate or not. My guess is that overall it's not really more accurate, since the proper simulation would be having our IOS HLE simulate IOS' dvd read strategy when files are accessed (in addition to something similar to what this commit does).

So, I'm not really in favor of the commit. However, if it is going to be committed, please make all the magic sizes be constant variables so that they have names.

JosJuice · 2015-05-09T15:44:46Z

The constants from VolumeWiiCrypted are now used, along with a SECTOR_SIZE constant.

JosJuice · 2016-03-01T22:19:02Z

A hardware test by @mmastrac showed that disc drive reads are aligned to 32 KiB, the size of an ECC block, which makes sense. Because of that, I've changed this PR from aligning to 2 KiB to aligning to 32 KiB. Also, I removed the - 2048 because it didn't exist in the test results as far as I understood them. There is still code that ensures that small sequential reads will be covered by the buffered code path.

This is a fairly large timing change for decrypted reads and a smaller timing change for non-decrypted reads.

It only roughly matches the last read offset. What we actually use it for is determining where the buffer got its data from.

JosJuice · 2017-02-10T14:53:27Z

PR #4829 makes half of this PR obsolete. The other half needs to be more or less rewritten. I'll open a new PR for that later.

magumagu reviewed Jan 17, 2015
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JosJuice force-pushed the dvd-timing-address-translation branch 3 times, most recently from 9cd445b to 33ef393 Compare January 17, 2015 21:08

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JosJuice force-pushed the dvd-timing-address-translation branch from 2596b32 to fe85daf Compare February 26, 2015 11:53

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JosJuice added 2 commits June 27, 2016 15:50

DVDInterface: Translate and align offsets for timing purposes

0848b88

This is a fairly large timing change for decrypted reads and a smaller timing change for non-decrypted reads.

DVDInterface: Rename s_last_read_offset for clarity

d786e88

It only roughly matches the last read offset. What we actually use it for is determining where the buffer got its data from.

JosJuice force-pushed the dvd-timing-address-translation branch from b605eed to d786e88 Compare June 27, 2016 13:53

JosJuice mentioned this pull request Jun 27, 2016

[WIP] Experimental DVD chunking #3701

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JosJuice closed this Feb 10, 2017

JosJuice deleted the dvd-timing-address-translation branch February 15, 2017 20:17

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DVDInterface: Translate and align offsets for timing purposes #1900

DVDInterface: Translate and align offsets for timing purposes #1900

JosJuice commented Jan 17, 2015

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JosJuice commented Jan 17, 2015

delroth commented Jan 17, 2015

Buddybenj commented Mar 16, 2015

skidau commented Mar 18, 2015

JosJuice commented Mar 18, 2015

shuffle2 commented May 8, 2015

JosJuice commented May 9, 2015

JosJuice commented Mar 1, 2016

JosJuice commented Feb 10, 2017

DVDInterface: Translate and align offsets for timing purposes #1900

DVDInterface: Translate and align offsets for timing purposes #1900

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JosJuice commented Jan 17, 2015

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JosJuice commented Jan 17, 2015

delroth commented Jan 17, 2015

Buddybenj commented Mar 16, 2015

skidau commented Mar 18, 2015

JosJuice commented Mar 18, 2015

shuffle2 commented May 8, 2015

JosJuice commented May 9, 2015

JosJuice commented Mar 1, 2016

JosJuice commented Feb 10, 2017