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From: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
To: linux-serial@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jirislaby@kernel.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	linux-kernel@vger.kernel.org
Cc: "Gilles BULOZ" <gilles.buloz@kontron.com>,
	"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>,
	stable@vger.kernel.org
Subject: [PATCH v2 4/4] serial: 8250: Flush DMA Rx on RLSI
Date: Tue,  8 Nov 2022 14:19:52 +0200	[thread overview]
Message-ID: <20221108121952.5497-5-ilpo.jarvinen@linux.intel.com> (raw)
In-Reply-To: <20221108121952.5497-1-ilpo.jarvinen@linux.intel.com>

Returning true from handle_rx_dma() without flushing DMA first creates
a data ordering hazard. If DMA Rx has handled any character at the
point when RLSI occurs, the non-DMA path handles any pending characters
jumping them ahead of those characters that are pending under DMA.

Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/tty/serial/8250/8250_port.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 92dd18716169..388172289627 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1901,10 +1901,9 @@ static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
 		if (!up->dma->rx_running)
 			break;
 		fallthrough;
+	case UART_IIR_RLSI:
 	case UART_IIR_RX_TIMEOUT:
 		serial8250_rx_dma_flush(up);
-		fallthrough;
-	case UART_IIR_RLSI:
 		return true;
 	}
 	return up->dma->rx_dma(up);
-- 
2.30.2


  parent reply	other threads:[~2022-11-08 12:20 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-08 12:19 [PATCH v2 0/4] 8250: DMA Fixes Ilpo Järvinen
2022-11-08 12:19 ` [PATCH v2 1/4] serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs Ilpo Järvinen
2022-11-08 12:19 ` [PATCH v2 2/4] serial: 8250_lpss: Configure DMA also w/o DMA filter Ilpo Järvinen
2022-11-08 12:19 ` [PATCH v2 3/4] serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake Ilpo Järvinen
2022-11-08 12:19 ` Ilpo Järvinen [this message]
2022-11-08 12:47 ` [PATCH v2 0/4] 8250: DMA Fixes Andy Shevchenko

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