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

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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.


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