From owner-svn-src-all@freebsd.org Sun Sep 29 02:55:57 2019 Return-Path: Delivered-To: svn-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id B78DEED60C; Sun, 29 Sep 2019 02:55:57 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 46gqsn4V1mz3yyg; Sun, 29 Sep 2019 02:55:57 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 7EB5FB61F; Sun, 29 Sep 2019 02:55:57 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id x8T2tvZS082190; Sun, 29 Sep 2019 02:55:57 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x8T2tvMh082189; Sun, 29 Sep 2019 02:55:57 GMT (envelope-from mav@FreeBSD.org) Message-Id: <201909290255.x8T2tvMh082189@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Sun, 29 Sep 2019 02:55:57 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r352861 - stable/12/sys/dev/uart X-SVN-Group: stable-12 X-SVN-Commit-Author: mav X-SVN-Commit-Paths: stable/12/sys/dev/uart X-SVN-Commit-Revision: 352861 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 29 Sep 2019 02:55:57 -0000 Author: mav Date: Sun Sep 29 02:55:57 2019 New Revision: 352861 URL: https://svnweb.freebsd.org/changeset/base/352861 Log: MFC r352369: Relax TX draining in ns8250_bus_transmit(). Since TX interrupt is generated when THRE is set, wait for TEMT set means wait for full character transmission time. At low speeds that may take awhile, burning CPU time while holding sc_hwmtx lock, also congested. This is partial revert of r317659. Modified: stable/12/sys/dev/uart/uart_dev_ns8250.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/dev/uart/uart_dev_ns8250.c ============================================================================== --- stable/12/sys/dev/uart/uart_dev_ns8250.c Sat Sep 28 23:08:19 2019 (r352860) +++ stable/12/sys/dev/uart/uart_dev_ns8250.c Sun Sep 29 02:55:57 2019 (r352861) @@ -1026,13 +1026,8 @@ ns8250_bus_transmit(struct uart_softc *sc) bas = &sc->sc_bas; uart_lock(sc->sc_hwmtx); - if (sc->sc_txdatasz > 1) { - if ((uart_getreg(bas, REG_LSR) & LSR_TEMT) == 0) - ns8250_drain(bas, UART_DRAIN_TRANSMITTER); - } else { - while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0) - DELAY(4); - } + while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0) + DELAY(4); for (i = 0; i < sc->sc_txdatasz; i++) { uart_setreg(bas, REG_DATA, sc->sc_txbuf[i]); uart_barrier(bas);