Re: [PATCH v1 5/5] tty: serial: 8250: add DFL bus driver for Altera 16550.

Andy Shevchenko
2022-09-06T20:24:57Z

On Tue, Sep 06, 2022 at 12:04:26PM -0700, matthew.gerlach@linux.intel.com wrote:
> From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
>
> Add a Device Feature List (DFL) bus driver for the Altera
> 16550 implementation of UART.

...

> +#include <linux/dfl.h>

> +#include <linux/version.h>

Hmm... Do we need this?

> +#include <linux/serial.h>
> +#include <linux/serial_8250.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/bitfield.h>
> +#include <linux/io-64-nonatomic-lo-hi.h>

Can this block be sorted alphabetically?

...

> +int feature_uart_walk(struct dfl_uart *dfluart, resource_size_t max)
> +{
> + void __iomem *param_base;
> + int off;
> + u64 v;
> +
> + v = readq(dfluart->csr_base + DFHv1_CSR_ADDR);
> + dfluart->csr_addr = FIELD_GET(DFHv1_CSR_ADDR_MASK, v);
> +
> + v = readq(dfluart->csr_base + DFHv1_CSR_SIZE_GRP);
> + dfluart->csr_size = FIELD_GET(DFHv1_CSR_SIZE_GRP_SIZE, v);
> +
> + if (dfluart->csr_addr == 0 || dfluart->csr_size == 0) {
> + dev_err(dfluart->dev, "FIXME bad dfh address and size\n");

DFH ?

> + return -EINVAL;
> + }
> +
> + if (!FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS, v)) {
> + dev_err(dfluart->dev, "missing required parameters\n");

Not sure I understood what parameters are here. FPGA VHDL? Configuration? RTL?

> + return -EINVAL;
> + }
> +
> + param_base = dfluart->csr_base + DFHv1_PARAM_HDR;
> +
> + off = dfl_find_param(param_base, max, DFHv1_PARAM_ID_CLK_FRQ);
> + if (off < 0) {
> + dev_err(dfluart->dev, "missing CLK_FRQ param\n");
> + return -EINVAL;
> + }
> +
> + dfluart->uart_clk = readq(param_base + off + DFHv1_PARAM_DATA);

> + dev_dbg(dfluart->dev, "UART_CLK_ID %llu Hz\n", dfluart->uart_clk);

Isn't this available via normal interfaces to user?

> + off = dfl_find_param(param_base, max, DFHv1_PARAM_ID_FIFO_LEN);
> + if (off < 0) {
> + dev_err(dfluart->dev, "missing FIFO_LEN param\n");
> + return -EINVAL;
> + }
> +
> + dfluart->fifo_len = readq(param_base + off + DFHv1_PARAM_DATA);
> + dev_dbg(dfluart->dev, "UART_FIFO_ID fifo_len %llu\n", dfluart->fifo_len);
> +
> + off = dfl_find_param(param_base, max, DFHv1_PARAM_ID_REG_LAYOUT);
> + if (off < 0) {
> + dev_err(dfluart->dev, "missing REG_LAYOUT param\n");
> + return -EINVAL;
> + }
> +
> + v = readq(param_base + off + DFHv1_PARAM_DATA);
> + dfluart->fifo_size = FIELD_GET(DFHv1_PARAM_ID_REG_WIDTH, v);
> + dfluart->reg_shift = FIELD_GET(DFHv1_PARAM_ID_REG_SHIFT, v);
> + dev_dbg(dfluart->dev, "UART_LAYOUT_ID width %d shift %d\n",
> + dfluart->fifo_size, dfluart->reg_shift);
> +
> + return 0;
> +}
> +
> +static int dfl_uart_probe(struct dfl_device *dfl_dev)
> +{
> + struct device *dev = &dfl_dev->dev;
> + struct uart_8250_port uart;
> + struct dfl_uart *dfluart;
> + int ret;
> +
> + memset(&uart, 0, sizeof(uart));
> +
> + dfluart = devm_kzalloc(dev, sizeof(*dfluart), GFP_KERNEL);
> + if (!dfluart)
> + return -ENOMEM;
> +
> + dfluart->csr_base = devm_ioremap_resource(dev, &dfl_dev->mmio_res);
> + if (IS_ERR(dfluart->csr_base)) {

> + dev_err(dev, "failed to get mem resource!\n");

The above call have a few different messages depending on error code.
No need to repeat this.

> + return PTR_ERR(dfluart->csr_base);
> + }
> +
> + dfluart->dev = dev;
> +
> + ret = feature_uart_walk(dfluart, resource_size(&dfl_dev->mmio_res));
> + if (ret < 0) {
> + dev_err(dev, "failed to uart feature walk %d\n", ret);

> + return -EINVAL;

Why shadowing error code?
What about

return dev_err_probe(dev, ret, ...);
?

> + }
> +
> + dev_dbg(dev, "nr_irqs %d %p\n", dfl_dev->num_irqs, dfl_dev->irqs);
> +
> + if (dfl_dev->num_irqs == 1)
> + uart.port.irq = dfl_dev->irqs[0];
> +
> + switch (dfluart->fifo_len) {
> + case 32:
> + uart.port.type = PORT_ALTR_16550_F32;
> + break;
> +
> + case 64:
> + uart.port.type = PORT_ALTR_16550_F64;
> + break;
> +
> + case 128:
> + uart.port.type = PORT_ALTR_16550_F128;
> + break;
> +
> + default:
> + dev_err(dev, "bad fifo_len %llu\n", dfluart->fifo_len);
> + return -EINVAL;
> + }
> +
> + uart.port.iotype = UPIO_MEM32;
> + uart.port.membase = dfluart->csr_base + dfluart->csr_addr;
> + uart.port.mapsize = dfluart->csr_size;
> + uart.port.regshift = dfluart->reg_shift;
> + uart.port.uartclk = dfluart->uart_clk;
> +
> + /* register the port */
> + ret = serial8250_register_8250_port(&uart);
> + if (ret < 0) {
> + dev_err(dev, "unable to register 8250 port %d.\n", ret);
> + return -EINVAL;
> + }
> + dev_info(dev, "serial8250_register_8250_port %d\n", ret);
> + dfluart->line = ret;
> + dev_set_drvdata(dev, dfluart);
> +
> + return 0;
> +}
> +
> +static void dfl_uart_remove(struct dfl_device *dfl_dev)
> +{
> + struct dfl_uart *dfluart = dev_get_drvdata(&dfl_dev->dev);
> +
> + if (dfluart->line > 0)
> + serial8250_unregister_port(dfluart->line);
> +}

...

> +#define FME_FEATURE_ID_UART 0x24

Purpose of this definition? For me with or without is still an ID.

> +static const struct dfl_device_id dfl_uart_ids[] = {
> + { FME_ID, FME_FEATURE_ID_UART },
> + { }
> +};

...

> +static struct dfl_driver dfl_uart_driver = {
> + .drv = {
> + .name = "dfl-uart",
> + },
> + .id_table = dfl_uart_ids,
> + .probe = dfl_uart_probe,
> + .remove = dfl_uart_remove,
> +};

> +

No need to have this blank line.

> +module_dfl_driver(dfl_uart_driver);

...

> +MODULE_DEVICE_TABLE(dfl, dfl_uart_ids);

Move this closer to the definition. That's how other drivers do in the kernel.

...

> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig

> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile

I know that the records in those files are not sorted, but can you try hard
to find the best place for them in those files from sorting point of view?

--
With Best Regards,
Andy Shevchenko