[PATCH v2 0/4] Fix transmit handling on SCI/RSCI ports

[Biju Das]

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.

To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
To: Jiri Slaby <jirislaby@xxxxxxxxxx>
To: Kiryl Shutsemau <kas@xxxxxxxxxx>
To: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
To: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-serial@xxxxxxxxxxxxxxx
CC: linux-renesas-soc@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: linux-coco@xxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx

---
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          |  2 ++
 drivers/tty/serial/sh-sci-common.h |  4 ++++
 drivers/tty/serial/sh-sci.c        | 45 +++++++++++++++++++++++++-------------
 3 files changed, 36 insertions(+), 15 deletions(-)
---
base-commit: 8f7df005a7564bd7ffa75da9c3085d5b996f1e16
change-id: 20261020-g2ul_sci-b610606ea5b5

Best regards,
-- 
Biju Das <biju.das.jz@xxxxxxxxxxxxxx>