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Date: Mon, 7 Feb 2022 18:29:32 -0500
From: Adrien Thierry <athierry@...hat.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
"linux-rpi-kernel@...ts.infradead.org"
<linux-rpi-kernel@...ts.infradead.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Jeremy Linton <jeremy.linton@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
Nicolas Saenz Julienne <nsaenz@...nel.org>,
Florian Fainelli <f.fainelli@...il.com>,
Ray Jui <rjui@...adcom.com>,
Scott Branden <sbranden@...adcom.com>,
"bcm-kernel-feedback-list@...adcom.com"
<bcm-kernel-feedback-list@...adcom.com>
Subject: 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 <athierry@...hat.com> 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.
> >
> > Signed-off-by: Adrien Thierry <athierry@...hat.com>
> > ---
> > 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()?
>
>
>
> > #include <linux/clk.h>
> > #include <linux/io.h>
> > #include <linux/module.h>
>
>
> property.h?
>
>
> > @@ -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?
>
>
>
> >
> > /* 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).
>
>
> > +
> > + /* 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;
>
>
>
>
> > + }
> > +
> > + 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.
>
>
> > 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
>
>
> +};
> > +
> > 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.
>
>
> > +};
> > +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
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