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Fix macOS mount bug (#424) - #448
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Read every whole sector of a READ10 chunk with one disk_read (CMD18) instead of one command per sector. On a Cardputer ADV with macOS 27 this takes a 16 MB read from 537 to 637 KB/s and the FSKit mount of a 62 GB card from 14.4 s to 13.2 s. Buffer MSC debug lines in RAM and write them to Launcher_error.log after USB mode ends and the card is remounted, instead of appending to the FAT volume while the host has it mounted. Refs bmorcelli#424
therezor
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Refs #424
USB mode now reads the SD card faster. The debug log no longer writes to the card while a computer is using it.
Tested on a Cardputer ADV, macOS 27.0.1, 62 GB SD card.
Why
macOS reads the whole FAT table before it mounts a card. If that takes too long, it gives up. That is what happened in #424, when the SD card ran at 4 MHz.
#439 and cd392f2 raised the SD clock, and main now mounts. But it is still close. After the card was unplugged without ejecting, macOS took about 30 s to check and mount it. The failed test in #424 gave up at about 24 s.
How
Faster reads. The computer asks for 8 sectors at a time. Launcher read them with 8 separate SD commands. Now it uses one command (CMD18).
Safer log. The debug log wrote to
Launcher_error.logwhile the computer had the card open, which can corrupt the card. Now the log stays in RAM and is saved after USB mode ends.Cost: +160 bytes flash, +1 KB RAM.
Tested
diskutil verifyVolumefound no errors.