serial: MPSC: Remove race between Rx stop & restart (6c1ead5e) · Commits · 戴 / test

The patch in commit ID 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 <carlos.sanchez@gecoinc.com> Signed-off-by:

Mark A. Greer <mgreer@mvista.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/mpsc.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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