Re: [PATCH v3 4/4] tty: serial: 8250: add DFL bus driver for Altera 16550.
From: Andy Shevchenko
Date: Tue Oct 04 2022 - 11:31:33 EST
On Tue, Oct 04, 2022 at 07:37:18AM -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.
...
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
https://docs.kernel.org/process/submitting-patches.html?highlight=reported#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes
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...
> + if (!dfhv1_has_params(dfh_base)) {
> + dev_err(dev, "missing required DFH parameters\n");
> + return -EINVAL;
> + }
Why not use dev_err_probe() everywhere since this is called only at ->probe()
stage?
...
> + 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;
Why error code is being shadowed?
> + }
...
> + 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;
Ditto.
> + }
...
> + 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;
> + }
Ditto.
...
> + dev_dbg(dev, "UART_LAYOUT_ID width %lld shift %d\n",
> + FIELD_GET(DFHv1_PARAM_ID_REG_WIDTH, v), (int)uart->port.regshift);
Casting in printf() in kernel in 99% shows the wrong specifier in use. Try to
select the best suitable one.
...
> + 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 it's temporary, may be you shouldn't even consider devm_ioremap_resource()
to begin with? The devm_* release type of functions in 99% of the cases
indicate of the abusing devm_.
> + if (ret < 0)
> + return dev_err_probe(dev, ret, "failed uart feature walk\n");
...
> + dev_info(dev, "serial8250_register_8250_port %d\n", dfluart->line);
Why do we need this noise?
...
> + if (dfluart->line >= 0)
When this can be false?
> + serial8250_unregister_port(dfluart->line);
...
> +config SERIAL_8250_DFL
> + tristate "DFL bus driver for Altera 16550 UART"
> + depends on SERIAL_8250 && FPGA_DFL
> + help
> + This option enables support for a Device Feature List (DFL) bus
> + driver for the Altera 16650 UART. One or more Altera 16650 UARTs
> + can be instantiated in a FPGA and then be discovered during
> + enumeration of the DFL bus.
When m, what be the module name?
...
> obj-$(CONFIG_SERIAL_8250_FOURPORT) += 8250_fourport.o
> obj-$(CONFIG_SERIAL_8250_ACCENT) += 8250_accent.o
> obj-$(CONFIG_SERIAL_8250_BOCA) += 8250_boca.o
> +obj-$(CONFIG_SERIAL_8250_DFL) += 8250_dfl.o
This group of drivers for the 4 UARTs on the board or so, does FPGA belong to
it? (Same Q, btw, for the Kconfig section. And yes, I know that some of the
entries are not properly placed there and in Makefile.)
> obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554) += 8250_exar_st16c554.o
> obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o
> obj-$(CONFIG_SERIAL_8250_FSL) += 8250_fsl.o
--
With Best Regards,
Andy Shevchenko