[PATCH v3 0/4] Fix transmit handling on SCI/RSCI ports

[Biju Das <biju.das.au@gmail.com>]

Hi All,

This series fixes several transmit problems on the SCI (PORT_SCI) and
RSCI ports of the sh-sci driver, seen on Renesas RZ SoCs:

 - Patch 1 removes the code that disables TE at the end of a
   transmission on SCI, which the hardware manual does not describe.
 - Patch 2 stops the TEI handler from turning the transmitter off
   while the xmit kfifo still holds data, which could stall or lose
   output. It also covers the TE handling that patch 1 no longer does
   in sci_transmit_chars().
 - Patch 3 skips the software clear of the TDxE flag on SCI, since
   hardware clears it on a TDR write and the extra clear caused a
   spurious TXI and a duplicated last character.
 - Patch 4 forces a TE toggle when restoring SCSCR in the console
   write path on SCI, so the TXI that restarts an interrupted drain is
   generated. Without it the RZ/G2UL console can hang during boot.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
Changes in v3:
 * Updated commit description for patch#2
 * When the port is stopped with data still queued, the transmit_chars()
   paths (sci_transmit_chars() and rsci_transmit_chars()) now also swap
   TIE for TEIE, as they already did for an empty kfifo. Without this, TIE
   would keep firing with nothing the driver is allowed to send, and TEI
   would never be raised to complete the transmission.
 * Replaced sci_tx_interrupt() with port's transmit_chars() to avoid
   lock drop race in sci_tx_end_interrupt() before TX handoff.
 * Added missing has_tdxe_auto_clear init in scix_early_console_setup().
 * Replaced to_sci_port(port)->type with sci_port->type in
   serial_console_write().
- Link to v2: https://lore.kernel.org/r/20261021-g2ul_sci-v2-0-b4e038220018@bp.renesas.com
Changes in v2:
 * Updated commit header and description for patch#2 and #3.
 * Take the port lock before reading the control register, so the
   read-modify-write in sci_tx_end_interrupt() is protected.
 * Extended the pending-data check in sci_tx_end_interrupt() to cover
   x_char and a stopped port, not only a non-empty xmit kfifo.
 * Replaced the PORT_SCI check with a has_tdxe_auto_clear flag in
   struct sci_port, set from the new tdxe_auto_clear field in
   struct sci_of_data.
- Link to v1: https://lore.kernel.org/r/20261019170139.473808-1-biju.das.jz@bp.renesas.com

---
Au Dang (2):
      serial: sh-sci: Skip TDxE clear when hardware clears it automatically
      serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI

Biju Das (2):
      serial: sh-sci: Drop TE disable at end of transmission on SCI
      serial: sh-sci: Keep TX enabled on TEI while data is pending

 drivers/tty/serial/rsci.c          |  4 ++-
 drivers/tty/serial/sh-sci-common.h |  4 +++
 drivers/tty/serial/sh-sci.c        | 71 ++++++++++++++++++++++++++------------
 3 files changed, 56 insertions(+), 23 deletions(-)
---
base-commit: 8f7df005a7564bd7ffa75da9c3085d5b996f1e16
change-id: 20261020-g2ul_sci-b610606ea5b5

Best regards,
-- 
Biju Das <biju.das.jz@bp.renesas.com>