serial: 8250_bcm2835aux: Add ACPI support

Add ACPI support to 8250_bcm2835aux driver. This makes it possible to
use the miniuart on the Raspberry Pi with the tianocore/edk2 UEFI
firmware.

Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Adrien Thierry <athierry@redhat.com>
Link: https://lore.kernel.org/r/20220207232129.402882-1-athierry@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
index fd95860cd6611e042f13d51dbc4567eee3c51047..2a1226a78a0c26492ce26ada9e8e36c49b56da7c 100644 (file)
--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -17,6 +17,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 
 #include "8250.h"
 
@@ -44,6 +45,10 @@ struct bcm2835aux_data {
        u32 cntl;
 };
 
+struct bcm2835_aux_serial_driver_data {
+       resource_size_t offset;
+};
+
 static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up)
 {
        if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
@@ -80,9 +85,12 @@ static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up)
 
 static int bcm2835aux_serial_probe(struct platform_device *pdev)
 {
+       const struct bcm2835_aux_serial_driver_data *bcm_data;
        struct uart_8250_port up = { };
        struct bcm2835aux_data *data;
+       resource_size_t offset = 0;
        struct resource *res;
+       unsigned int uartclk;
        int ret;
 
        /* allocate the custom structure */
@@ -109,9 +117,7 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
        platform_set_drvdata(pdev, data);
 
        /* get the clock - this also enables the HW */
-       data->clk = devm_clk_get(&pdev->dev, NULL);
-       if (IS_ERR(data->clk))
-               return dev_err_probe(&pdev->dev, PTR_ERR(data->clk), "could not get clk\n");
+       data->clk = devm_clk_get_optional(&pdev->dev, NULL);
 
        /* get the interrupt */
        ret = platform_get_irq(pdev, 0);
@@ -125,8 +131,24 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
                dev_err(&pdev->dev, "memory resource not found");
                return -EINVAL;
        }
-       up.port.mapbase = res->start;
-       up.port.mapsize = resource_size(res);
+
+       bcm_data = device_get_match_data(&pdev->dev);
+
+       /* Some UEFI implementations (e.g. tianocore/edk2 for the Raspberry Pi)
+        * describe the miniuart with a base address that encompasses the auxiliary
+        * registers shared between the miniuart and spi.
+        *
+        * This is due to historical reasons, see discussion here :
+        * https://edk2.groups.io/g/devel/topic/87501357#84349
+        *
+        * We need to add the offset between the miniuart and auxiliary
+        * registers to get the real miniuart base address.
+        */
+       if (bcm_data)
+               offset = bcm_data->offset;
+
+       up.port.mapbase = res->start + offset;
+       up.port.mapsize = resource_size(res) - offset;
 
        /* Check for a fixed line number */
        ret = of_alias_get_id(pdev->dev.of_node, "serial");
@@ -141,12 +163,19 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
                return ret;
        }
 
+       uartclk = clk_get_rate(data->clk);
+       if (!uartclk) {
+               ret = device_property_read_u32(&pdev->dev, "clock-frequency", &uartclk);
+               if (ret)
+                       return dev_err_probe(&pdev->dev, ret, "could not get clk rate\n");
+       }
+
        /* the HW-clock divider for bcm2835aux is 8,
         * but 8250 expects a divider of 16,
         * so we have to multiply the actual clock by 2
         * to get identical baudrates.
         */
-       up.port.uartclk = clk_get_rate(data->clk) * 2;
+       up.port.uartclk = uartclk * 2;
 
        /* register the port */
        ret = serial8250_register_8250_port(&up);
@@ -173,16 +202,27 @@ static int bcm2835aux_serial_remove(struct platform_device *pdev)
        return 0;
 }
 
+static const struct bcm2835_aux_serial_driver_data bcm2835_acpi_data = {
+       .offset = 0x40,
+};
+
 static const struct of_device_id bcm2835aux_serial_match[] = {
        { .compatible = "brcm,bcm2835-aux-uart" },
        { },
 };
 MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match);
 
+static const struct acpi_device_id bcm2835aux_serial_acpi_match[] = {
+       { "BCM2836", (kernel_ulong_t)&bcm2835_acpi_data },
+       { }
+};
+MODULE_DEVICE_TABLE(acpi, bcm2835aux_serial_acpi_match);
+
 static struct platform_driver bcm2835aux_serial_driver = {
        .driver = {
                .name = "bcm2835-aux-uart",
                .of_match_table = bcm2835aux_serial_match,
+               .acpi_match_table = bcm2835aux_serial_acpi_match,
        },
        .probe  = bcm2835aux_serial_probe,
        .remove = bcm2835aux_serial_remove,