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

matthew.gerlach
2022-09-08T18:26:56Z

On Tue, 6 Sep 2022, Andy Shevchenko wrote:

> 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?

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
>
>
>