linux-kernel - [PATCH v4] serial: 8250_bcm7271: improve bcm7271 8250 port

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Date:   Mon, 21 Aug 2023 11:52:51 -0700
From:   Justin Chen <justin.chen@...adcom.com>
To:     linux-serial@...r.kernel.org
Cc:     Justin Chen <justin.chen@...adcom.com>,
        Al Cooper <alcooperx@...il.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        John Ogness <john.ogness@...utronix.de>,
        Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>,
        linux-kernel@...r.kernel.org (open list:TTY LAYER)
Subject: [PATCH v4] serial: 8250_bcm7271: improve bcm7271 8250 port

The 8250 BCM7271 UART is not a direct match to PORT_16550A and other
generic ports do not match its hardware capabilities. PORT_ALTR matches
the rx trigger levels, but its vendor configurations are not compatible.
Unfortunately this means we need to create another port to fully capture
the hardware capabilities of the BCM7271 UART.

To alleviate some latency pressures, we default the rx trigger level to 8.

Signed-off-by: Justin Chen <justin.chen@...adcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
Acked-by: Doug Berger <opendmb@...il.com>
---
v4
	- Switch PORT_BCM7271 back to 76

v3
	- Switch PORT_BCM7271 to 13
	- Added trailing comma to struct declaration

v2
	- Switch PORT_BCM7271 to 76
	- Elaborated commit message
	- Renamed port name

 drivers/tty/serial/8250/8250_bcm7271.c | 4 +---
 drivers/tty/serial/8250/8250_port.c    | 8 ++++++++
 include/uapi/linux/serial_core.h       | 3 +++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index d4b05d7ad9e8..aa5aff046756 100644
--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -1042,7 +1042,7 @@ static int brcmuart_probe(struct platform_device *pdev)
 	dev_dbg(dev, "DMA is %senabled\n", priv->dma_enabled ? "" : "not ");
 
 	memset(&up, 0, sizeof(up));
-	up.port.type = PORT_16550A;
+	up.port.type = PORT_BCM7271;
 	up.port.uartclk = clk_rate;
 	up.port.dev = dev;
 	up.port.mapbase = mapbase;
@@ -1056,8 +1056,6 @@ static int brcmuart_probe(struct platform_device *pdev)
 		| UPF_FIXED_PORT | UPF_FIXED_TYPE;
 	up.port.dev = dev;
 	up.port.private_data = priv;
-	up.capabilities = UART_CAP_FIFO | UART_CAP_AFE;
-	up.port.fifosize = 32;
 
 	/* Check for a fixed line number */
 	ret = of_alias_get_id(np, "serial");
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 16aeb1420137..7fb1d7c00001 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -322,6 +322,14 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes   = {2, 66, 130, 194},
 		.flags          = UART_CAP_FIFO,
 	},
+	[PORT_BCM7271] = {
+		.name		= "Broadcom BCM7271 UART",
+		.fifo_size	= 32,
+		.tx_loadsz	= 32,
+		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01,
+		.rxtrig_bytes	= {1, 8, 16, 30},
+		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
+	},
 };
 
 /* Uart divisor latch read */
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index 281fa286555c..7e66067b6c06 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -144,6 +144,9 @@
 /* Blackfin bf5xx */
 #define PORT_BFIN	75
 
+/* Broadcom BCM7271 UART */
+#define PORT_BCM7271	76
+
 /* Broadcom SB1250, etc. SOC */
 #define PORT_SB1250_DUART	77
 
-- 
2.7.4


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