linux-kernel - [PATCH v2 3/4] serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake

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Date:   Tue,  8 Nov 2022 14:19:51 +0200
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     linux-serial@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Cc:     Gilles BULOZ <gilles.buloz@...tron.com>, stable@...r.kernel.org,
        Wentong Wu <wentong.wu@...el.com>
Subject: [PATCH v2 3/4] serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake

Configure DMA to use 16B burst size with Elkhart Lake. This makes the
bus use more efficient and works around an issue which occurs with the
previously used 1B.

The fix was initially developed by Srikanth Thokala and Aman Kumar.
This together with the previous config change is the cleaned up version
of the original fix.

Fixes: 0a9410b981e9 ("serial: 8250_lpss: Enable DMA on Intel Elkhart Lake")
Cc: <stable@...r.kernel.org> # serial: 8250_lpss: Configure DMA also w/o DMA filter
Reported-by: Wentong Wu <wentong.wu@...el.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/tty/serial/8250/8250_lpss.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 7d9cddbfef40..0e43bdfb7459 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -174,6 +174,8 @@ static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
 	 */
 	up->dma = dma;
 
+	lpss->dma_maxburst = 16;
+
 	port->set_termios = dw8250_do_set_termios;
 
 	return 0;
-- 
2.30.2