On Tue, 1 Nov 2022, matthew.gerlach@xxxxxxxxxxxxxxx wrote: > > > On Tue, 1 Nov 2022, Xu Yilun wrote: > > > On 2022-10-31 at 17:34:39 -0700, matthew.gerlach@xxxxxxxxxxxxxxx wrote: > > > > > > > > > On Sat, 29 Oct 2022, Xu Yilun wrote: > > > > > > > On 2022-10-20 at 14:26:10 -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. > > > > > > > > > > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx> > > > > > --- > > > > > v4: use dev_err_probe() everywhere that is appropriate > > > > > clean up noise > > > > > change error messages to use the word, unsupported > > > > > tried again to sort Makefile and KConfig better > > > > > reorder probe function for easier error handling > > > > > use new dfh_find_param API > > > > > > > > > > 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 | 149 > > > > > +++++++++++++++++++++++++++++ > > > > > drivers/tty/serial/8250/Kconfig | 12 +++ > > > > > drivers/tty/serial/8250/Makefile | 1 + > > > > > 3 files changed, 162 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..f02f0ba2a565 > > > > > --- /dev/null > > > > > +++ b/drivers/tty/serial/8250/8250_dfl.c > > > > > @@ -0,0 +1,149 @@ > > > > > +// SPDX-License-Identifier: GPL-2.0 > > > > > +/* > > > > > + * Driver for FPGA UART > > > > > + * > > > > > + * Copyright (C) 2022 Intel Corporation, Inc. > > > > > + * > > > > > + * Authors: > > > > > + * Ananda Ravuri <ananda.ravuri@xxxxxxxxx> > > > > > + * Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx> > > > > > + */ > > > > > + > > > > > +#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 { > > > > > + int line; > > > > > +}; > > > > > + > > > > > +static int dfl_uart_get_params(struct dfl_device *dfl_dev, struct > > > > > uart_8250_port *uart) > > > > > +{ > > > > > + struct device *dev = &dfl_dev->dev; > > > > > + u64 v, fifo_len, reg_width; > > > > > + u64 *p; > > > > > + > > > > > + p = dfh_find_param(dfl_dev, DFHv1_PARAM_ID_CLK_FRQ); > > > > > + if (!p) > > > > > + return dev_err_probe(dev, -EINVAL, "missing CLK_FRQ > > > > > param\n"); > > > > > + > > > > > + uart->port.uartclk = *p; > > > > > + dev_dbg(dev, "UART_CLK_ID %u Hz\n", uart->port.uartclk); > > > > > + > > > > > + p = dfh_find_param(dfl_dev, DFHv1_PARAM_ID_FIFO_LEN); > > > > > + if (!p) > > > > > + return dev_err_probe(dev, -EINVAL, "missing FIFO_LEN > > > > > param\n"); > > > > > + > > > > > + fifo_len = *p; > > > > > + 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: > > > > > + return dev_err_probe(dev, -EINVAL, "unsupported > > > > > fifo_len %llu\n", fifo_len); > > > > > + } > > > > > + > > > > > + p = dfh_find_param(dfl_dev, DFHv1_PARAM_ID_REG_LAYOUT); > > > > > + if (!p) > > > > > + return dev_err_probe(dev, -EINVAL, "missing REG_LAYOUT > > > > > param\n"); > > > > > + > > > > > + v = *p; > > > > > + uart->port.regshift = FIELD_GET(DFHv1_PARAM_ID_REG_SHIFT, v); > > > > > + reg_width = FIELD_GET(DFHv1_PARAM_ID_REG_WIDTH, v); > > > > > > > > I have concern that the raw layout inside the parameter block is > > > > still exposed to drivers and need to be parsed by each driver. > > > > > > Raw parameter block will always have to be passed to the driver because HW > > > specific properties can be defined that will need to be parsed by the > > > specific driver. > > > > So there is a question about the scope of the definitions of these parameter > > blocks. MSIX seems globally used across all dfl devices. REG_LAYOUT > > seems specific to uart? > > There are definitely two classes of parameter blocks. One class is HW > agnostic parameters where the parameters are relevant to many different kinds > of HW components. MSI-X, and input clock-frequency are certainly HW agnostic, > and it turns out that REG_LAYOUT is not specific to uart. You can see > reg_bits and reg_stride in struct regmap_config. There are also device tree > bindings for reg-shift and reg-io-width. The second class of parameters would > be specific to HW component. In the case of this uart driver, all parameters > would be considered HW agnostic parameters. > > > > > If a parameter block is widely used in dfl drivers, duplicate the parsing > > from HW layout in each driver may not be a good idea. While for device > > specific parameter block, it's OK. > > It sounds like we are in agreement. > > > > > Another concern is the indexing of the parameter IDs. If some parameter > > blocks should be device specific, then no need to have globally indexed > > parameter IDs. Index them locally in device is OK. So put the definitions > > of ID values, HW layout and their parsing operation in each driver. > > It may be confusing for two drivers to use the same parameter id that have > different meanings and data layout. Since all the parameters for this driver > would be considered HW agnostic, we'd don't need to address this issue with > this patchset. > > > > > How about we define HW agnostic IDs for parameter specific fields like: > > > > > > > > PARAM_ID FIELD_ID > > > > ================================ > > > > MSIX STARTV > > > > NUMV > > > > -------------------------------- > > > > CLK FREQ > > > > -------------------------------- > > > > FIFO LEN > > > > -------------------------------- > > > > REG_LAYOUT WIDTH > > > > SHIFT > > > > > > > > And define like u64 dfl_find_param(struct dfl_device *, int param_id, > > > > int field_id) > > > > > > I don't think dfl_find_param as defined above adds much value. > > > > > > > > > > > Think further, if we have to define HW agnostic property - value pairs, > > > > why don't we just use "Software nodes for the firmware node", see > > > > drivers/base/swnode.c. I think this may be a better choice. > > > > > > I am looking into "Software nodes for the firmware node", and it can be > > > used > > > for HW agnostic properties. Each dfl driver will still have to make a > > > function call to fetch each HW agnostice property value as well as a > > > function call to find the HW specific parameters and then parse those > > > parameters. Btw, another aspect this discussion has completely overlooked is the presence of parameter version and how it impacts data layout. Is v1 always going be a subset of v2 or can a later version remove something v1 had? -- i.