Re: [PATCH v3] serial: 8250_bcm2835aux: Add ACPI support

[Jeremy Linton]

Hi,

On 2/7/22 17:21, Adrien Thierry wrote:
> 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.

I merged this to 5.17rc3, switched the console to this device and it now 
works in linux! Thanks for doing this!

Tested-by: Jeremy Linton <jeremy.linton@xxxxxxx>

> Signed-off-by: Adrien Thierry <athierry@xxxxxxxxxx>
> ---
> V1 -> V2: Refactored code to remove unnecessary conditional paths and
> intermediate variables
> V2 -> V3: Cleaned up coding style and addressed review comments
>
>   drivers/tty/serial/8250/8250_bcm2835aux.c | 52 ++++++++++++++++++++---
>   1 file changed, 46 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
> index fd95860cd661..2a1226a78a0c 100644
> --- 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,
>
> base-commit: 2ade8eef993c37a2a43e51a9b1f6c25509a2acce