Re: [PATCH v2] serial: 8250_bcm2835aux: Add ACPI support

On Sat, Feb 05, 2022 at 01:58:43AM +0200, Andy Shevchenko wrote:

On Thursday, February 3, 2022, Adrien Thierry [off-list ref] wrote:

quoted

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.

Signed-off-by: Adrien Thierry <redacted>
---
V1 -> V2: Refactored code to remove unnecessary conditional paths and
intermediate variables

 drivers/tty/serial/8250/8250_bcm2835aux.c | 87 ++++++++++++++++++-----
 1 file changed, 69 insertions(+), 18 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c

b/drivers/tty/serial/8250/8250_bcm2835aux.c
index fd95860cd661..b7cec2a3b5f7 100644

--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c

@@ -12,6 +12,7 @@
  * simultaneously to rs485.
  */

+#include <linux/acpi.h>

For what purposes?
Can’t you use device_get_match_data()?

quoted

 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/module.h>

property.h?

quoted

@@ -44,6 +45,10 @@ struct bcm2835aux_data {
        u32 cntl;
 };

+struct bcm2835_aux_serial_acpi_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)) {

@@ -82,8 +87,11 @@ static int bcm2835aux_serial_probe(struct

platform_device *pdev)
 {
        struct uart_8250_port up = { };
        struct bcm2835aux_data *data;
+       struct bcm2835_aux_serial_acpi_driver_data *acpi_data;
        struct resource *res;
        int ret;
+       resource_size_t offset = 0;
+       unsigned int uartclk;

Keep reversed Xmas tree order?

quoted

        /* allocate the custom structure */
        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);

@@ -110,8 +118,11 @@ static int bcm2835aux_serial_probe(struct

platform_device *pdev)

        /* 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");
+       if (IS_ERR(data->clk)) {
+               ret = device_property_read_u32(&pdev->dev,
"clock-frequency", &uartclk);
+               if (ret)
+                       return dev_err_probe(&pdev->dev, ret, "could not
get clk\n");
+       }

        /* get the interrupt */
        ret = platform_get_irq(pdev, 0);

@@ -125,20 +136,47 @@ 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);
-
-       /* Check for a fixed line number */
-       ret = of_alias_get_id(pdev->dev.of_node, "serial");
-       if (ret >= 0)
-               up.port.line = ret;
-
-       /* enable the clock as a last step */
-       ret = clk_prepare_enable(data->clk);
-       if (ret) {
-               dev_err(&pdev->dev, "unable to enable uart clock - %d\n",
-                       ret);
-               return ret;
+
+       if (has_acpi_companion(&pdev->dev)) {
+               const struct acpi_device_id *match;
+
+               match = acpi_match_device(pdev->dev.driver->acpi_match_table,
&pdev->dev);
+               if (!match)
+                       return -ENODEV;
+
+               acpi_data = (struct bcm2835_aux_serial_acpi_driver_data
*)match->driver_data;

acpi_data naming is fragile. Use something with local namespace or without
it completely (bcm_data, data, ddata, etc).

quoted

+
+               /* 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.
+                */
+               offset = acpi_data->offset;

quoted

+       }
+
+       up.port.mapbase = res->start + offset;
+       up.port.mapsize = resource_size(res) - offset;
+
+       if (dev_of_node(&pdev->dev)) {
+               /* Check for a fixed line number */
+               ret = of_alias_get_id(pdev->dev.of_node, "serial");
+               if (ret >= 0)
+                       up.port.line = ret;
+
+               /* enable the clock as a last step */
+               ret = clk_prepare_enable(data->clk);
+               if (ret) {
+                       dev_err(&pdev->dev, "unable to enable uart clock -
%d\n",
+                               ret);
+                       return ret;
+               }
+
+               uartclk = clk_get_rate(data->clk);
        }

        /* the HW-clock divider for bcm2835aux is 8,

@@ -146,7 +184,7 @@ static int bcm2835aux_serial_probe(struct

platform_device *pdev)
         * 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);

@@ -159,7 +197,9 @@ static int bcm2835aux_serial_probe(struct

platform_device *pdev)
        return 0;

 dis_clk:
-       clk_disable_unprepare(data->clk);
+       if (dev_of_node(&pdev->dev))
+               clk_disable_unprepare(data->clk);
+

Why do you change this? CCF is null-aware.

quoted

        return ret;
 }

@@ -173,16 +213,27 @@ static int bcm2835aux_serial_remove(struct

platform_device *pdev)
        return 0;
 }

+static const struct bcm2835_aux_serial_acpi_driver_data
bcm2835_acpi_data = {
+       .offset = 0x40

 + comma


+};

quoted

+
 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 },
+       { },

No comma for terminator entry.

quoted

+};
+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,

base-commit: 1f2cfdd349b7647f438c1e552dc1b983da86d830
--
2.34.1

-- 
With Best Regards,
Andy Shevchenko

Thanks for your feedback! I've submitted a v3 addressing your comments.

Adrien