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serial: apple-dockchannel: don't stall boot when no debug host reads the console - #943
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DjDeveloperr
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Approved.
The J714sAP console DT has set apple,tx-never-wait on the DockChannel console since 11-08, with this exact code. That covers every M5 Pro RAM boot and the M5's default boot from its internal SSD. Console input and output work with the debug host attached, including long dmesg dumps.
Not tested: a boot with nothing reading the debug port.
Merges cleanly into current integration/aurora.
…r-wait The DockChannel console drains only while a debug USB host reads the channel. With none attached, as on an M5 Ultra Mac Studio (J775D) that boots unattended, the TX FIFO stays full: the write loops spun up to 10000 reads of TX_FREE per character and every close waited for output that could not drain, so boot and every console write stalled. With apple,tx-never-wait, console writes (the driver's and the early console's) send what TX_FREE says fits and drop the rest, tty output is sent from the drain timer and dropped after two ticks without room, a close does not wait, and tx_empty reports empty. Without the property, every other DockChannel Mac's driver and early console behave as before. Testing: J775D boots unattended to its login with nothing reading the channel (the property set), and with a reader attached the console carries the whole boot log. Signed-off-by: Jeff Queisser <funkzy@users.noreply.github.com> Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Erik Bourget <erik@ebourget.net>
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Rebased onto integration/aurora (8d98b7a). The old head 8eda590 is kept as Why: the first CI run on this branch failed dt-checks with 42 new warnings ( So 29ccbef is dropped, and integration's description stays ("Transmit completes without waiting for a reader to drain the channel, so a console with nobody attached does not stall"). The driver commit is unchanged by the rebase (now 923e129, same author). integration had the property but no driver support, so this PR still adds the behaviour. The three driver files are byte-identical to the DockChannel console the M5 Pro boots with. CI is running on the new head. 🤖 Generated with Claude Code |
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Retested before merging on the M5 Pro (J714sAP, bare metal, SSD boot), kernel 7.3.0-m5-merge: the M5's integration kernel with this round's rebased heads in place of the old ones (every PR's own patch identical to what is merged; logs in work/m5-pr-merge-20261109). CI green. Before merging, this round (these 14 PRs, #1323 and the rebased #1254/#1306/#938/#1316/#1199) was test-merged in order onto integration/aurora f9cf6f9 with no conflicts:
🤖 Generated with Claude Code |
A DockChannel UART drains only while a debug USB host reads it. On a Mac that boots unattended with nothing attached, the TX FIFO stays full: every console character spun up to 10000 times and every close waited for output that never drained, so boot stalled.
apple,tx-never-waitmakes console writes send what fits and drop the rest, and tty output drop after two drain ticks without room. Boards without the property are unchanged.Commits by Jeff Queisser, for J775D, which boots unattended with nothing on its debug port.
Created with Claude Opus 5.5 in Claude Code.