Re: [PATCH v3 4/4] tty: serial: 8250: add DFL bus driver for Altera 16550.

[matthew . gerlach]

On Wed, 5 Oct 2022, Ilpo Järvinen wrote:

> On Tue, 4 Oct 2022, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
>
> > From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> >
> > Add a Device Feature List (DFL) bus driver for the Altera
> > 16550 implementation of UART.
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> > v3: use passed in location of registers
> >     use cleaned up functions for parsing parameters
> >
> > v2: clean up error messages
> >     alphabetize header files
> >     fix 'missing prototype' error by making function static
> >     tried to sort Makefile and Kconfig better
> > ---
> >  drivers/tty/serial/8250/8250_dfl.c | 177 +++++++++++++++++++++++++++++
> >  drivers/tty/serial/8250/Kconfig    |   9 ++
> >  drivers/tty/serial/8250/Makefile   |   1 +
> >  3 files changed, 187 insertions(+)
> >  create mode 100644 drivers/tty/serial/8250/8250_dfl.c
> >
> > diff --git a/drivers/tty/serial/8250/8250_dfl.c b/drivers/tty/serial/8250/8250_dfl.c
> > new file mode 100644
> > index 000000000000..110ad3a73459
> > --- /dev/null
> > +++ b/drivers/tty/serial/8250/8250_dfl.c
> > @@ -0,0 +1,177 @@
>
> > +static int dfl_uart_get_params(struct device *dev, void __iomem *dfh_base, resource_size_t max,
> > +			       struct uart_8250_port *uart)
> > +{
> > +	u64 v, fifo_len, reg_width;
> > +	int off;
> > +
> > +	if (!dfhv1_has_params(dfh_base)) {
> > +		dev_err(dev, "missing required DFH parameters\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	off = dfhv1_find_param(dfh_base, max, DFHv1_PARAM_ID_CLK_FRQ);
> > +	if (off < 0) {
> > +		dev_err(dev, "missing CLK_FRQ param\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	uart->port.uartclk = readq(dfh_base + off);
> > +	dev_dbg(dev, "UART_CLK_ID %u Hz\n", uart->port.uartclk);
> > +
> > +	off = dfhv1_find_param(dfh_base, max, DFHv1_PARAM_ID_FIFO_LEN);
> > +	if (off < 0) {
> > +		dev_err(dev, "missing FIFO_LEN param\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	fifo_len = readq(dfh_base + off);
> > +	dev_dbg(dev, "UART_FIFO_ID fifo_len %llu\n", fifo_len);
> > +
> > +	switch (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", fifo_len);
>
> I'd tell user "unsupported" rather than "bad".

The word, unsupported, sounds better.  I will change it in both places you 
suggested.

> > +		return -EINVAL;
> > +	}
> > +
> > +	off = dfhv1_find_param(dfh_base, max, DFHv1_PARAM_ID_REG_LAYOUT);
> > +	if (off < 0) {
> > +		dev_err(dev, "missing REG_LAYOUT param\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	v = readq(dfh_base + off);
> > +	uart->port.regshift = FIELD_GET(DFHv1_PARAM_ID_REG_SHIFT, v);
> > +	reg_width = FIELD_GET(DFHv1_PARAM_ID_REG_WIDTH, v);
> > +
> > +	dev_dbg(dev, "UART_LAYOUT_ID width %lld shift %d\n",
> > +		FIELD_GET(DFHv1_PARAM_ID_REG_WIDTH, v), (int)uart->port.regshift);
>
> Why not use reg_width directly?

Good catch.

> > +	switch (reg_width) {
> > +	case 4:
> > +		uart->port.iotype = UPIO_MEM32;
> > +		break;
> > +
> > +	case 2:
> > +		uart->port.iotype = UPIO_MEM16;
> > +		break;
> > +
> > +	default:
> > +		dev_err(dev, "invalid reg_width %lld\n", reg_width);
>
> unsupported ?
>
> > +		return -EINVAL;
> > +	}
> > +
> > +	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;
> > +	resource_size_t res_size;
> > +	void __iomem *dfh_base;
> > +	int ret;
> > +
> > +	memset(&uart, 0, sizeof(uart));
> > +	uart.port.flags = UPF_IOREMAP;
> > +	uart.port.mapbase = dfl_dev->csr_res.start;
> > +	uart.port.mapsize = resource_size(&dfl_dev->csr_res);
> > +
> > +	dfluart = devm_kzalloc(dev, sizeof(*dfluart), GFP_KERNEL);
> > +	if (!dfluart)
> > +		return -ENOMEM;
> > +
> > +	dfh_base = devm_ioremap_resource(dev, &dfl_dev->mmio_res);
> > +	if (IS_ERR(dfh_base))
> > +		return PTR_ERR(dfh_base);
> > +
> > +	res_size = resource_size(&dfl_dev->mmio_res);
> > +
> > +	ret = dfl_uart_get_params(dev, dfh_base, res_size, &uart);
> > +
> > +	devm_iounmap(dev, dfh_base);
> > +	devm_release_mem_region(dev, dfl_dev->mmio_res.start, res_size);
> > +
> > +	if (ret < 0)
> > +		return dev_err_probe(dev, ret, "failed uart feature walk\n");
> > +
> > +	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];
> > +
> > +	/* register the port */
>
> This comment is pretty useless. Just drop it.

Will drop this useless comment.

> > +	dfluart->line = serial8250_register_8250_port(&uart);
> > +	if (dfluart->line < 0)
> > +		return dev_err_probe(dev, dfluart->line, "unable to register 8250 port.\n");
> > +
> > +	dev_info(dev, "serial8250_register_8250_port %d\n", dfluart->line);
>
> This you want to drop too. It seems a debug thing rather than info level
> stuff.

It is actually redundant output because serial8250_register_8250_port() 
produces useful output.  I will drop the line.

> --
> i.