From cb2da74905c1cf6e0cc1d91f347030fa1e12cc81 Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Thu, 11 May 2023 14:03:51 -0600
Subject: [PATCH] stand: eficom: Don't preemtively assume flow control

Remove rtsdtr_off. It's basically unused. Expand its meaning, but put
changing flow control to under an ifdef. We shouldn't set it unless
we're sure we need to do so. UEFI normally initializes the device
correctly, and we should avoid needless changes that aren't user
requested.

Sponsored by:		Netflix
Reviewed by:		tsoome
Differential Revision:	https://reviews.freebsd.org/D40009
---
 stand/efi/libefi/eficom.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/stand/efi/libefi/eficom.c b/stand/efi/libefi/eficom.c
index 8d14209f8484..b0fc0d8fbf6a 100644
--- a/stand/efi/libefi/eficom.c
+++ b/stand/efi/libefi/eficom.c
@@ -47,7 +47,6 @@ struct serial {
 	uint32_t	databits;
 	EFI_PARITY_TYPE	parity;
 	EFI_STOP_BITS_TYPE stopbits;
-	uint32_t	rtsdtr_off;	/* boolean */
 	int		ioaddr;		/* index in handles array */
 	EFI_HANDLE	currdev;	/* current serial device */
 	EFI_HANDLE	condev;		/* EFI Console device */
@@ -275,7 +274,6 @@ comc_probe(struct console *sc)
 	comc_port->databits = 8;
 	comc_port->parity = DefaultParity;
 	comc_port->stopbits = DefaultStopBits;
-	comc_port->rtsdtr_off = 0;		/* rts-dtr is on */
 
 	handle = NULL;
 	env = getenv("efi_com_port");
@@ -515,7 +513,6 @@ static bool
 comc_setup(void)
 {
 	EFI_STATUS status;
-	UINT32 control;
 	char *ev;
 
 	/* port is not usable */
@@ -544,18 +541,17 @@ comc_setup(void)
 			return (false);
 	}
 
+#ifdef EFI_FORCE_RTS
 	if (comc_port->sio->GetControl != NULL && comc_port->sio->SetControl != NULL) {
+		UINT32 control;
+
 		status = comc_port->sio->GetControl(comc_port->sio, &control);
 		if (EFI_ERROR(status))
 			return (false);
-		if (comc_port->rtsdtr_off) {
-			control &= ~(EFI_SERIAL_REQUEST_TO_SEND |
-			    EFI_SERIAL_DATA_TERMINAL_READY);
-		} else {
-			control |= EFI_SERIAL_REQUEST_TO_SEND;
-		}
+		control |= EFI_SERIAL_REQUEST_TO_SEND;
 		(void) comc_port->sio->SetControl(comc_port->sio, control);
 	}
+#endif
 	/* Mark this port usable. */
 	eficom.c_flags |= (C_PRESENTIN | C_PRESENTOUT);
 	return (true);