Re: [PATCH v1 5/5] tty: serial: 8250: add DFL bus driver for Altera 16550.
From: matthew . gerlach
Date: Thu Sep 08 2022 - 14:27:00 EST
On Tue, 6 Sep 2022, Andy Shevchenko wrote:
On Tue, Sep 06, 2022 at 12:04:26PM -0700, 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.
...
+#include <linux/dfl.h>
+#include <linux/version.h>
Hmm... Do we need this?
We do not 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?
Yes, they can and should 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 ?
Yes,"DFH" is better than "dfh" in the message.
+ 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?
How about "missing required DFH parameters\n"?
+ 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?
I am not sure what "normal interfaces to user" you are referring to. The
code is just trying to read the frequency of the input clock to the uart
from a DFH paramter.
+ 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.
I will remove the call to dev_err().
+ 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, ...);
?
Using dev_err_probe seems like the way to go.
+ }
+
+ 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.
I don't think I understand the question. Is the name of the macro unclear,
or do you think it is not necessary?
+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.
I will remove the 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.
Thanks for the suggestion.
...
--- 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?
I will try to find a better place from sorting porint of view.
--
With Best Regards,
Andy Shevchenko