linux-kernel - [PATCH 2/4] serial: 8250_lpss: Configure DMA also w/o DMA filter

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Date:   Mon,  7 Nov 2022 13:07:06 +0200
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     stable <stable@...nel.org>
Subject: [PATCH 2/4] serial: 8250_lpss: Configure DMA also w/o DMA filter

If the platform doesn't use DMA device filter (as is the case with
Elkhart Lake), whole lpss8250_dma_setup() setup is skipped. This
results in skipping also *_maxburst setup which is undesirable.
Refactor lpss8250_dma_setup() to configure DMA even if filter is not
setup.

Cc: stable <stable@...nel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/tty/serial/8250/8250_lpss.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 44cc755b1a29..ed281445a97d 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -277,8 +277,10 @@ static int lpss8250_dma_setup(struct lpss8250 *lpss, struct uart_8250_port *port
 	struct dw_dma_slave *rx_param, *tx_param;
 	struct device *dev = port->port.dev;
 
-	if (!lpss->dma_param.dma_dev)
-		return 0;
+	if (!lpss->dma_param.dma_dev) {
+		dma = port->dma;
+		goto confonly;
+	}
 
 	rx_param = devm_kzalloc(dev, sizeof(*rx_param), GFP_KERNEL);
 	if (!rx_param)
@@ -289,16 +291,20 @@ static int lpss8250_dma_setup(struct lpss8250 *lpss, struct uart_8250_port *port
 		return -ENOMEM;
 
 	*rx_param = lpss->dma_param;
-	dma->rxconf.src_maxburst = lpss->dma_maxburst;
-
 	*tx_param = lpss->dma_param;
-	dma->txconf.dst_maxburst = lpss->dma_maxburst;
 
 	dma->fn = lpss8250_dma_filter;
 	dma->rx_param = rx_param;
 	dma->tx_param = tx_param;
 
 	port->dma = dma;
+
+confonly:
+	if (dma) {
+		dma->rxconf.src_maxburst = lpss->dma_maxburst;
+		dma->txconf.dst_maxburst = lpss->dma_maxburst;
+	}
+
 	return 0;
 }
 
-- 
2.30.2