Re: [PATCH v2 6/6] tty: serial: 8250: add DFL bus driver for Altera 16550.

[Xu Yilun <yilun.xu@intel.com>]

On 2022-09-23 at 05:17:45 -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.
> 
> Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> Reported-by: kernel test robot <lkp@intel.com>
> ---
> 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 +
>  include/linux/dfl.h                |   7 ++
>  4 files changed, 194 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..539ca6138eda
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_dfl.c
> @@ -0,0 +1,177 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for FPGA UART
> + *
> + * Copyright (C) 2022 Intel Corporation, Inc.
> + *
> + * Authors:
> + *   Ananda Ravuri <ananda.ravuri@intel.com>
> + *   Matthew Gerlach <matthew.gerlach@linux.intel.com>
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/dfl.h>
> +#include <linux/io-64-nonatomic-lo-hi.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/serial.h>
> +#include <linux/serial_8250.h>
> +
> +struct dfl_uart {
> +	void __iomem   *csr_base;
> +	struct device  *dev;
> +	u64             uart_clk;
> +	u64             fifo_len;
> +	unsigned int    fifo_size;
> +	unsigned int    reg_shift;
> +	unsigned int    line;
> +};
> +
> +static 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_SIZE_GRP);
> +
> +	if (!FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS, v)) {
> +		dev_err(dfluart->dev, "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);

I think the parameters of dfl_find_param are too complicated to be used
outside dfl framework (It is OK for dfl internal use).

How about:

  dfl_find_param(struct dfl_device *ddev, int param_id)

Thanks,
Yilun