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Message-ID: <CAHp75VckYiBccVN+_K+Tm38kcdC10=sekQZg7Uz_HwS4xyW2UA@mail.gmail.com>
Date: Wed, 5 Apr 2017 13:54:20 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Joel Stanley <joel@....id.au>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.com>,
Mark Rutland <mark.rutland@....com>,
Rob Herring <robh+dt@...nel.org>, Jeremy Kerr <jk@...abs.org>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
devicetree <devicetree@...r.kernel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
openbmc@...ts.ozlabs.org
Subject: Re: [PATCH v2 2/2] drivers/serial: Add driver for Aspeed virtual UART
On Wed, Apr 5, 2017 at 7:03 AM, Joel Stanley <joel@....id.au> wrote:
> From: Jeremy Kerr <jk@...abs.org>
>
> 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.
I would go with vUART abbreviation, but it's up to you.
>
> The VUART is two UART 'front ends' connected by their FIFO (no actual
> serial line in between). One is on the BMC side (management controller)
> and one is on the host CPU side.
>
> This driver is for the BMC side. The sysfs files allow the BMC
> userspace, which owns the system configuration policy, to specify at
> what IO port and interrupt number the host side will appear to the host
> on the Host <-> BMC LPC bus. It could be different on a different system
> (though most of them use 3f8/4).
>
> 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.
> - Move to 8250 directory
> - Rename ast -> aspeed to match other Aspeed drivers
> drivers/tty/serial/8250/aspeed-vuart.c | 341 +++++++++++++++++++++
There is a pattern 8250_x[_y].c
So, I would go with 8250_aspeed_virt.c or 8250_aspeed_vuart.c or alike.
> +config SERIAL_8250_ASPEED_VUART
> + tristate "Aspeed Virtual UART"
> + depends on SERIAL_8250
> + depends on OF
> + * 2 of the License, or (at your option) any later version.
> + *
Redundant line.
> + */
> +#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>
> +static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,
> + bool discard)
> +{
> + u8 reg;
> +
> + reg = readb(vuart->regs + ASPEED_VUART_GCRA);
> +
> + /* if the HOST_TX_DISCARD bit is set, discard is *disabled* */
Perhaps "disabled" for better readability?
> + reg &= ~ASPEED_VUART_GCRA_HOST_TX_DISCARD;
> + if (!discard)
> + reg |= ASPEED_VUART_GCRA_HOST_TX_DISCARD;
> +
> + writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
> +}
> +static int aspeed_vuart_probe(struct platform_device *pdev)
> +{
> + struct uart_8250_port port;
> + struct resource *res;
> + struct aspeed_vuart *vuart;
> + struct device_node *np;
Longest line upper.
> + u32 clk, prop;
> + int rc;
> +
> + np = pdev->dev.of_node;
> +
> + vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);
> + if (!vuart)
> + return -ENOMEM;
> +
> + vuart->dev = &pdev->dev;
> +
> + /* The 8510 core creates the mapping, which we grab a reference to
> + * for VUART-specific registers */
/*
* Multi-line comments.
* Look like this.
*/
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + vuart->regs = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(vuart->regs))
> + return PTR_ERR(vuart->regs);
> +
> + memset(&port, 0, sizeof(port));
> + port.port.private_data = vuart;
> + port.port.membase = vuart->regs;
> + port.port.mapbase = res->start;
> + port.port.mapsize = resource_size(res);
> + port.port.startup = aspeed_vuart_startup;
> + port.port.shutdown = aspeed_vuart_shutdown;
> + port.port.dev = &pdev->dev;
> +
> + rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
> + if (rc < 0)
> + return rc;
> +
> + 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;
> +
> + /* 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);
Isn't better to get this via platform_get_irq() ?
> + port.port.irqflags = IRQF_SHARED;
> + port.port.iotype = UPIO_MEM;
> + if (of_property_read_u32(np, "reg-io-width", &prop) == 0) {
I would still go with usual pattern.
> + 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;
Hmm... And this one is not in align with IO accessors used in this
driver. (readx()/writex() are little endian IO accessors).
> + 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_property_read_bool(np, "no-loopback-test"))
> + port.port.flags |= UPF_SKIP_TEST;
> +
> + if (port.port.fifosize)
> + port.capabilities = UART_CAP_FIFO;
> +
> + if (of_property_read_bool(np, "auto-flow-control"))
> + port.capabilities |= UART_CAP_AFE;
--
With Best Regards,
Andy Shevchenko
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