From: sashiko-bot@kernel.org
To: "Biju Das" <biju.das.au@gmail.com>
Cc: linux-serial@vger.kernel.org
Subject: Re: [PATCH v2 4/4] serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI
Date: Wed, 21 Oct 2026 13:19:18 +0000 [thread overview]
Message-ID: <sashiko-outbox-180294@kernel.org> (raw)
In-Reply-To: <20261021-g2ul_sci-v2-4-b4e038220018@bp.renesas.com>
> From: Au Dang <au.dang.jx@renesas.com>
>
> When SCI0 (PORT_SCI) is the system console on RZ/G2UL, the board can
> hang at the serial console output stage during boot.
>
> ftrace shows the following sequence:
>
> 1. sci_transmit_chars() is draining the TX kfifo through TXI
> interrupts with SCSCR=0xf0 (TE=1, TIE=1, RE=1, RIE=1).
>
> 2. serial_console_write() runs in the middle of that drain. It saves
> SCSCR=0xf0, switches to polling by writing SCSCR=0x30 (TE=1, TIE=0)
> and outputs the characters with sci_poll_put_char().
>
> 3. It then restores SCSCR=0xf0 in a single write. TE is 1 both before
> [ ... ]
> TIE is being re-enabled, so TXI fires and the interrupted drain
> resumes.
>
> Signed-off-by: Au Dang <au.dang.jx@renesas.com>
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261021-g2ul_sci-v2-0-b4e038220018@bp.renesas.com?part=4
prev parent reply other threads:[~2026-10-21 13:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 13:13 [PATCH v2 0/4] Fix transmit handling on SCI/RSCI ports Biju Das
2026-10-21 13:13 ` [PATCH v2 1/4] serial: sh-sci: Drop TE disable at end of transmission on SCI Biju Das
2026-10-21 13:18 ` sashiko-bot
2026-10-21 13:13 ` [PATCH v2 2/4] serial: sh-sci: Keep TX enabled on TEI while data is pending Biju Das
2026-10-21 13:38 ` sashiko-bot
2026-10-22 10:28 ` Biju Das
2026-10-21 13:13 ` [PATCH v2 3/4] serial: sh-sci: Skip TDxE clear when hardware clears it automatically Biju Das
2026-10-21 13:22 ` sashiko-bot
2026-10-22 10:29 ` Biju Das
2026-10-21 13:13 ` [PATCH v2 4/4] serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI Biju Das
2026-10-21 13:19 ` sashiko-bot [this message]
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