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SubjectRe: [PATCH 2/2] drivers/serial: Add driver for Aspeed virtual UART
On Tue, Mar 28, 2017 at 8:44 AM, Joel Stanley <joel@jms.id.au> wrote:
> This change adds a driver for the 16550-based Aspeed virtual UART
> device. We use a similar process to the of_serial driver for device
> probe, but expose some VUART-specific functions through sysfs too.
>
> OpenPOWER host firmware doesn't like it when the host-side of the
> VUART's FIFO is not drained. This driver only disables host TX discard
> mode when the port is in use. We set the VUART enabled bit when we bind
> to the device, and clear it on unbind.
>
> We don't want to do this on open/release, as the host may be using this
> bit to configure serial output modes, which is independent of whether
> the devices has been opened by BMC userspace.

> Documentation/devicetree/bindings/serial/8250.txt | 2 +
> drivers/tty/serial/Kconfig | 10 +
> drivers/tty/serial/Makefile | 1 +
> drivers/tty/serial/aspeed-vuart.c | 335 ++++++++++++++++++++++

And why it's not under 8250 folder?

> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_platform.h>
> +#include <linux/clk.h>
> +
> +#include "8250/8250.h"
> +
> +#define AST_VUART_GCRA 0x20

> +#define AST_VUART_GCRA_VUART_EN 0x01
> +#define AST_VUART_GCRA_HOST_TX_DISCARD 0x20

BIT(x) ?

> +#define AST_VUART_GCRB 0x24

> +#define AST_VUART_GCRB_HOST_SIRQ_MASK 0xf0

GENMASK() ?

> +#define AST_VUART_GCRB_HOST_SIRQ_SHIFT 4
> +#define AST_VUART_ADDRL 0x28
> +#define AST_VUART_ADDRH 0x2c
> +
> +struct ast_vuart {

> + struct platform_device *pdev;

Ususally there is no need to keep pointer to sturct platform_device,
rahter we need struct device *dev.

> + void __iomem *regs;
> + struct clk *clk;
> + int line;
> +};
> +
> +static ssize_t ast_vuart_show_addr(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct ast_vuart *vuart = dev_get_drvdata(dev);
> + u16 addr;
> +

> + addr = (readb(vuart->regs + AST_VUART_ADDRH) << 8) |
> + (readb(vuart->regs + AST_VUART_ADDRL));

It looks like you have register shift 2 bits and byte accessors. We
have some helpers for that (serial_in() / serial_out() or alike).

> +
> + return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
> +}
> +
> +static ssize_t ast_vuart_set_addr(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct ast_vuart *vuart = dev_get_drvdata(dev);
> + unsigned long val;
> + int err;
> +
> + err = kstrtoul(buf, 0, &val);
> + if (err)
> + return err;
> +

> + writeb((val >> 8) & 0xff, vuart->regs + AST_VUART_ADDRH);
> + writeb((val >> 0) & 0xff, vuart->regs + AST_VUART_ADDRL);

Useless & 0xff.

> +
> + return count;
> +}

> +}
> +
> +

Extra empty line.

> +/**

If you are going to use kernel doc do it in accordance with howto.

> + * The device tree parsing code here is heavily based on that of the of_serial
> + * driver, but we have a few core differences, as we need to use our own
> + * ioremapping for extra register support
> + */

> +static int ast_vuart_probe(struct platform_device *pdev)
> +{
> + struct uart_8250_port port;
> + struct resource resource;
> + struct ast_vuart *vuart;
> + struct device_node *np;
> + u32 clk, prop;
> + int rc;
> +

> + np = pdev->dev.of_node;

And if np == NULL?

> +
> + vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);
> + if (!vuart)
> + return -ENOMEM;
> +
> + vuart->pdev = pdev;


> + rc = of_address_to_resource(np, 0, &resource);
> + if (rc) {
> + dev_warn(&pdev->dev, "invalid address\n");
> + return rc;
> + }
> +
> + /* create our own mapping for VUART-specific registers */
> + vuart->regs = devm_ioremap_resource(&pdev->dev, &resource);
> + if (IS_ERR(vuart->regs)) {
> + dev_warn(&pdev->dev, "failed to map registers\n");
> + return PTR_ERR(vuart->regs);
> + }

Can you use platform_get-resource() + devm_ioremap_resource() ?
If no, why?

> +
> + memset(&port, 0, sizeof(port));
> + port.port.private_data = vuart;
> + port.port.membase = vuart->regs;
> + port.port.mapbase = resource.start;
> + port.port.mapsize = resource_size(&resource);
> + port.port.startup = ast_vuart_startup;
> + port.port.shutdown = ast_vuart_shutdown;
> +
> + if (of_property_read_u32(np, "clock-frequency", &clk)) {
> + vuart->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(vuart->clk)) {
> + dev_warn(&pdev->dev,
> + "clk or clock-frequency not defined\n");
> + return PTR_ERR(vuart->clk);
> + }
> +
> + rc = clk_prepare_enable(vuart->clk);
> + if (rc < 0)
> + return rc;
> +
> + clk = clk_get_rate(vuart->clk);
> + }
> +

> + /* If current-speed was set, then try not to change it. */
> + if (of_property_read_u32(np, "current-speed", &prop) == 0)
> + port.port.custom_divisor = clk / (16 * prop);
> +
> + /* Check for shifted address mapping */
> + if (of_property_read_u32(np, "reg-offset", &prop) == 0)
> + port.port.mapbase += prop;
> +
> + /* Check for registers offset within the devices address range */
> + if (of_property_read_u32(np, "reg-shift", &prop) == 0)
> + port.port.regshift = prop;
> +
> + /* Check for fifo size */
> + if (of_property_read_u32(np, "fifo-size", &prop) == 0)
> + port.port.fifosize = prop;

Perhaps you need other way around, check for error and supply a
default in such case.

> +
> + /* Check for a fixed line number */
> + rc = of_alias_get_id(np, "serial");
> + if (rc >= 0)
> + port.port.line = rc;
> +
> + port.port.irq = irq_of_parse_and_map(np, 0);

> + port.port.irqflags = IRQF_SHARED;

This is set by core. You already supplied correct flag for that below.

> + port.port.iotype = UPIO_MEM;
> + if (of_property_read_u32(np, "reg-io-width", &prop) == 0) {

You hide an error code from of_property_read_u32() here. Why?

And if there is an error you are continuing with what? 0?

> + switch (prop) {
> + case 1:
> + port.port.iotype = UPIO_MEM;
> + break;
> + case 4:
> + port.port.iotype = of_device_is_big_endian(np) ?
> + UPIO_MEM32BE : UPIO_MEM32;
> + break;
> + default:
> + dev_warn(&pdev->dev, "unsupported reg-io-width (%d)\n",
> + prop);
> + rc = -EINVAL;
> + goto err_clk_disable;
> + }
> + }
> +
> + port.port.type = PORT_16550A;
> + port.port.uartclk = clk;
> + port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
> + | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST;
> +

> + if (of_find_property(np, "no-loopback-test", NULL))
> + port.port.flags |= UPF_SKIP_TEST;

You perhaps meant _read_bool() for sake of consistency.

> +
> + port.port.dev = &pdev->dev;
> +
> + if (port.port.fifosize)
> + port.capabilities = UART_CAP_FIFO;
> +

> + if (of_property_read_bool(pdev->dev.of_node,
> + "auto-flow-control"))

One line?

> + port.capabilities |= UART_CAP_AFE;
> +
> + rc = serial8250_register_8250_port(&port);
> + if (rc < 0)
> + goto err_clk_disable;
> +
> +
> + vuart->line = rc;
> + ast_vuart_set_enabled(vuart, true);
> + ast_vuart_set_host_tx_discard(vuart, true);
> + platform_set_drvdata(pdev, vuart);
> +
> + /* extra sysfs control */
> + rc = device_create_file(&pdev->dev, &dev_attr_lpc_address);
> + if (rc)
> + dev_warn(&pdev->dev, "can't create lpc_address file\n");
> + rc = device_create_file(&pdev->dev, &dev_attr_sirq);
> + if (rc)
> + dev_warn(&pdev->dev, "can't create sirq file\n");
> +
> + return 0;
> +
> +err_clk_disable:
> + if (vuart->clk)
> + clk_disable_unprepare(vuart->clk);
> +
> + irq_dispose_mapping(port.port.irq);
> + return rc;
> +}
> +
> +static int ast_vuart_remove(struct platform_device *pdev)
> +{
> + struct ast_vuart *vuart = platform_get_drvdata(pdev);
> +
> + ast_vuart_set_enabled(vuart, false);
> +
> + if (vuart->clk)
> + clk_disable_unprepare(vuart->clk);
> + return 0;
> +}

--
With Best Regards,
Andy Shevchenk

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