From owner-svn-src-head@freebsd.org Sun Sep 15 23:56:40 2019 Return-Path: Delivered-To: svn-src-head@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 964C7EBE92; Sun, 15 Sep 2019 23:56:40 +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 46WmVw3VX1z3NYf; Sun, 15 Sep 2019 23:56:40 +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 5B321FEB7; Sun, 15 Sep 2019 23:56:40 +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 x8FNueld070713; Sun, 15 Sep 2019 23:56:40 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x8FNuen4070712; Sun, 15 Sep 2019 23:56:40 GMT (envelope-from mav@FreeBSD.org) Message-Id: <201909152356.x8FNuen4070712@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Sun, 15 Sep 2019 23:56:40 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r352369 - head/sys/dev/uart X-SVN-Group: head X-SVN-Commit-Author: mav X-SVN-Commit-Paths: head/sys/dev/uart X-SVN-Commit-Revision: 352369 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 15 Sep 2019 23:56:40 -0000 Author: mav Date: Sun Sep 15 23:56:39 2019 New Revision: 352369 URL: https://svnweb.freebsd.org/changeset/base/352369 Log: 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. PR: 240121 MFC after: 2 weeks Modified: head/sys/dev/uart/uart_dev_ns8250.c Modified: head/sys/dev/uart/uart_dev_ns8250.c ============================================================================== --- head/sys/dev/uart/uart_dev_ns8250.c Sun Sep 15 21:32:19 2019 (r352368) +++ head/sys/dev/uart/uart_dev_ns8250.c Sun Sep 15 23:56:39 2019 (r352369) @@ -1029,13 +1029,8 @@ 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);