From: sashiko-bot@kernel.org
To: Biju <biju.das.au@gmail.com>
Cc: linux-serial@vger.kernel.org
Subject: Re: [PATCH 4/4] serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI
Date: Mon, 19 Oct 2026 17:08:20 +0000 [thread overview]
Message-ID: <sashiko-outbox-177999@kernel.org> (raw)
In-Reply-To: <20261019170139.473808-5-biju.das.jz@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/20261019170139.473808-1-biju.das.jz@bp.renesas.com?part=4
prev parent reply other threads:[~2026-10-19 17:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-19 17:01 [PATCH 0/4] Fix transmit handling on SCI/RSCI ports Biju
2026-10-19 17:01 ` [PATCH 1/4] serial: sh-sci: Drop TE disable at end of transmission on SCI Biju
2026-10-19 17:07 ` sashiko-bot
2026-10-19 17:01 ` [PATCH 2/4] serial: sh-sci: Don’t disable TX on TEI while the xmit kfifo still holds data Biju
2026-10-19 17:17 ` sashiko-bot
2026-10-20 15:23 ` Biju Das
2026-10-19 17:01 ` [PATCH 3/4] serial: sh-sci: Skip TDxE status clear for PORT_SCI Biju
2026-10-19 17:19 ` sashiko-bot
2026-10-20 15:28 ` Biju Das
2026-10-20 8:36 ` Geert Uytterhoeven
2026-10-20 9:40 ` Biju Das
2026-10-19 17:01 ` [PATCH 4/4] serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI Biju
2026-10-19 17:08 ` sashiko-bot [this message]
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