From: Carlos Sanchez Date: Tue, 31 Jul 2007 07:38:59 +0000 (-0700) Subject: serial: MPSC: Remove race between Rx stop & restart X-Git-Tag: v2.6.23-rc2~71 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6c1ead5e77c4e41d58ae6e6c3285ad38275df4a8;p=linux-2.6 serial: MPSC: Remove race between Rx stop & restart The patch in commit ID f7232056bff5fe2d3bfeab35252a66ebaeb5bbde stops (aborts) the MPSC's receive engine just before restarting it. Unfortunately, it doesn't wait for the abort to complete before restarting it which creates a race between the abort and the restart. If the restart occurs first, the in-progress abort stops it again and the rx engine remains stopped. Instead, do the abort when the SDMA engine is being stopped. Make sure to wait for the abort to complete before continuing. Signed-off-by: Carlos Sanchez Signed-off-by: Mark A. Greer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c index 00924feaf6..567fa789c5 100644 --- a/drivers/serial/mpsc.c +++ b/drivers/serial/mpsc.c @@ -1363,8 +1363,6 @@ mpsc_start_rx(struct mpsc_port_info *pi) { pr_debug("mpsc_start_rx[%d]: Starting...\n", pi->port.line); - /* Issue a Receive Abort to clear any receive errors */ - writel(MPSC_CHR_2_RA, pi->mpsc_base + MPSC_CHR_2); if (pi->rcv_data) { mpsc_enter_hunt(pi); mpsc_sdma_cmd(pi, SDMA_SDCM_ERD); @@ -1379,6 +1377,20 @@ mpsc_stop_rx(struct uart_port *port) pr_debug("mpsc_stop_rx[%d]: Stopping...\n", port->line); + if (pi->mirror_regs) { + writel(pi->MPSC_CHR_2_m | MPSC_CHR_2_RA, + pi->mpsc_base + MPSC_CHR_2); + /* Erratum prevents reading CHR_2 so just delay for a while */ + udelay(100); + } + else { + writel(readl(pi->mpsc_base + MPSC_CHR_2) | MPSC_CHR_2_RA, + pi->mpsc_base + MPSC_CHR_2); + + while (readl(pi->mpsc_base + MPSC_CHR_2) & MPSC_CHR_2_RA) + udelay(10); + } + mpsc_sdma_cmd(pi, SDMA_SDCM_AR); return; }