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Received-SPF: Pass (protection.outlook.com: domain of renesas.com designates 8.62.32.50 as permitted sender) receiver=protection.outlook.com; client-ip=8.62.32.50; helo=ejcrelay004p.adwin.renesas.com; pr=E Received: from ejcrelay004p.adwin.renesas.com (8.62.32.50) by TY2PEPF00005624.mail.protection.outlook.com (10.167.240.55) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.21.615.4 via Frontend Transport; Fri, 13 Nov 2026 18:30:47 +0000 Received: from [192.168.1.82] (DEU-5CG2204K0P.adwin.renesas.com [10.226.92.17]) by ejcrelay004p.adwin.renesas.com (Postfix) with ESMTP id F2596300022F; Sat, 14 Nov 2026 03:30:43 +0900 (JST) From: Diogo Ivo Date: Fri, 13 Nov 2026 18:26:31 +0000 Subject: [PATCH v4 6/7] serial: sh-sci: Toggle TE when restoring SCSCR in console write on SCI X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261113-g2ul_sci-v4-6-6815e41d90c5@renesas.com> References: <20261113-g2ul_sci-v4-0-6815e41d90c5@renesas.com> In-Reply-To: <20261113-g2ul_sci-v4-0-6815e41d90c5@renesas.com> To: Greg Kroah-Hartman , Jiri Slaby Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Biju Das , Au Dang , Geert Uytterhoeven , Wolfram Sang , Lad Prabhakar , Thierry Bultel , Diogo Ivo X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 1nyjP76bytSVbhC9frS/dCWFnUa6I/tjCrzgxuJ8ci9/BIdyr2U9gxyXkqxrsQWXw29gtqI7fteOI6KInLCXze1HxS4J8jluYLASdiW11q35GxYPm4xExcDGAk/TMwRXtQda6QX9hq0s6ybhexAA8oGVEfgXwcNXYlvW3OD8NcHNRxeXGfS+AgtAxYT9gtCXE5NKQy3pceD3KaZJ0g7F8IzI6beBD08Bh95cMqWp2SPw24DSTkNOk5zqvBDZl7zOL87iAwVQ7Qq5YILS8iA5sGfFaycmlzocx1MyuNM5ytKAkOkA/kJtJLWkyefgxyNNFNX74/osXobcnczPvmzZceU1d2OR5hIsGVoCnJGBvN4AJd4F2RQS63CeAogS6mz36gtvwL9CmhkhS7sqSL7zd14ymmAjGrB/N+Npann7xg3CHbDNWCQ3RIQNlIwB7gVV X-OriginatorOrg: renesas.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Nov 2026 18:30:47.9094 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9d4eba41-93ae-40e2-92f4-08df41b43cc8 X-MS-Exchange-CrossTenant-Id: 53d82571-da19-47e4-9cb4-625a166a4a2a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=53d82571-da19-47e4-9cb4-625a166a4a2a;Ip=[8.62.32.50];Helo=[ejcrelay004p.adwin.renesas.com] X-MS-Exchange-CrossTenant-AuthSource: TY2PEPF00005624.JPNP286.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: OS3PR01MB8459 From: Au Dang 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 and after, so there is no TE transition. 4. sci_start_tx() is then called repeatedly with SCSCR unchanged, but no TXI is ever raised again, so the drain never resumes and the console hangs. The RZ/G2UL User's Manual (section 23.3.6, "SCI Initialization") notes that changing SCR.TE from 1 to 0 or from 0 to 1 while SCR.TIE is 1 generates a TXI interrupt request. Without a TE transition, the TXI that would restart the drain is never generated. For PORT_SCI, restore SCSCR in two steps: first with TE cleared, then with the full saved value. This forces the TE 1->0->1 transition while TIE is being re-enabled, so TXI fires and the interrupted drain resumes. Signed-off-by: Au Dang Signed-off-by: Biju Das Signed-off-by: Diogo Ivo --- drivers/tty/serial/sh-sci.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index fc77536644ed..2d667086ec3a 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -3456,10 +3456,14 @@ static void serial_console_write(struct console *co, const char *s, cpu_relax(); /* restore the SCSCR */ - if (sci_port->ops->finish_console_write) + if (sci_port->ops->finish_console_write) { sci_port->ops->finish_console_write(port, ctrl); - else + } else { + if (sci_port->type == PORT_SCI) + sci_port->ops->write_reg(port, regs->control, ctrl & ~SCSCR_TE); + sci_port->ops->write_reg(port, regs->control, ctrl); + } if (locked) uart_port_unlock_irqrestore(port, flags); -- 2.56.0