[PATCH v3] lib: utils: Add LiteX UART support
Jessica Clarke
jrtc27 at jrtc27.com
Sat Nov 13 14:12:48 PST 2021
On 13 Nov 2021, at 22:07, Gabriel L. Somlo <gsomlo at gmail.com> wrote:
>
> Hi Xiang,
>
> On Sat, 13 Nov 2021 13:57:03 +0800, wxjstz at 126.com wrote:
>> 在 2021-11-12星期五的 10:03 -0500，Gabriel Somlo写道：
>>> This patch adds support for the UART provided by the LiteX
>>> SoC framework (https://github.com/enjoy-digital/litex),
>>> based its FDT info described in the Linux sources at
>>> Documentation/devicetree/bindings/serial/litex,liteuart.yaml).
>>>
>>> Signed-off-by: Gabriel Somlo <gsomlo at gmail.com>
>>> ---
>>>
>>> New in v3:
>>> - less verbose / more concise commit blurb :)
>>> - fixed serial_litex_init() alignment
>>> - fixed `uart_base` pointer arithmetic
>>> - treat single-bit registers as Boolean
>>> - removed access to `event` (irq-related) register
>>> (not needed since UART is operated in polling mode)
>>>
>>>> New in v2:
>>>> - remove properties (and parameters) not actually used by the
>>>> LiteX UART
>>>> - remove redundant parentheses from pointer arithmetic
>>>> (thanks jrtc27!)
>>>>
>>>>> See https://github.com/litex-hub/linux-on-litex-rocket for instructions
>>>>> on how to build a LiteX+Rocket bitstream for e.g. the nexys4ddr (Xilinx
>>>>> Artix7 FPGA dev board), and https://pastebin.com/nu1dSE16 for a demo of
>>>>> the board booting a linux payload via opensbi, using this patch.
>>>
>>> include/sbi_utils/fdt/fdt_helper.h | 3 ++
>>> include/sbi_utils/serial/litex-uart.h | 17 ++++++++
>>> lib/utils/fdt/fdt_helper.c | 19 ++++++++
>>> lib/utils/serial/fdt_serial.c | 2 +
>>> lib/utils/serial/fdt_serial_litex.c | 35 +++++++++++++++
>>> lib/utils/serial/litex-uart.c | 62 +++++++++++++++++++++++++++
>>> lib/utils/serial/objects.mk | 2 +
>>> 7 files changed, 140 insertions(+)
>>> create mode 100644 include/sbi_utils/serial/litex-uart.h
>>> create mode 100644 lib/utils/serial/fdt_serial_litex.c
>>> create mode 100644 lib/utils/serial/litex-uart.c
>>>
>>> diff --git a/include/sbi_utils/fdt/fdt_helper.h b/include/sbi_utils/fdt/fdt_helper.h
>>> index 24fee7a..5f75f07 100644
>>> --- a/include/sbi_utils/fdt/fdt_helper.h
>>> +++ b/include/sbi_utils/fdt/fdt_helper.h
>>> @@ -62,6 +62,9 @@ int fdt_parse_shakti_uart_node(void *fdt, int nodeoffset,
>>> int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
>>> struct platform_uart_data *uart);
>>>
>>> +int fdt_parse_litex_uart_node(void *fdt, int nodeoffset,
>>> + struct platform_uart_data *uart);
>>> +
>>> int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
>>> struct platform_uart_data *uart);
>>>
>>> diff --git a/include/sbi_utils/serial/litex-uart.h b/include/sbi_utils/serial/litex-uart.h
>>> new file mode 100644
>>> index 0000000..91ab644
>>> --- /dev/null
>>> +++ b/include/sbi_utils/serial/litex-uart.h
>>> @@ -0,0 +1,17 @@
>>> +/*
>>> + * SPDX-License-Identifier: BSD-2-Clause
>>> + *
>>> + * Copyright (c) 2021 Gabriel Somlo
>>> + *
>>> + * Authors:
>>> + * Gabriel Somlo <gsomlo at gmail.com>
>>> + */
>>> +
>>> +#ifndef __SERIAL_LITEX_UART_H__
>>> +#define __SERIAL_LITEX_UART_H__
>>> +
>>> +#include <sbi/sbi_types.h>
>>> +
>>> +int litex_uart_init(unsigned long base);
>>> +
>>> +#endif
>>> diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
>>> index 5bf4021..a42f53b 100644
>>> --- a/lib/utils/fdt/fdt_helper.c
>>> +++ b/lib/utils/fdt/fdt_helper.c
>>> @@ -403,6 +403,25 @@ int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
>>> return 0;
>>> }
>>>
>>> +int fdt_parse_litex_uart_node(void *fdt, int nodeoffset,
>>> + struct platform_uart_data *uart)
>>> +{
>>> + int rc;
>>> + uint64_t reg_addr, reg_size;
>>> +
>>> + if (nodeoffset < 0 || !uart || !fdt)
>>> + return SBI_ENODEV;
>>> +
>>> + rc = fdt_get_node_addr_size(fdt, nodeoffset, 0, ®_addr, ®_size);
>>> + if (rc < 0 || !reg_addr || !reg_size)
>>> + return SBI_ENODEV;
>>> + uart->addr = reg_addr;
>>> +
>>> + /* LiteX UART has no further configurable properties */
>>> +
>>> + return 0;
>>> +}
>>> +
>>> int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
>>> struct platform_uart_data *uart)
>>> {
>>> diff --git a/lib/utils/serial/fdt_serial.c b/lib/utils/serial/fdt_serial.c
>>> index cedda04..f73d26a 100644
>>> --- a/lib/utils/serial/fdt_serial.c
>>> +++ b/lib/utils/serial/fdt_serial.c
>>> @@ -15,6 +15,7 @@
>>>
>>> extern struct fdt_serial fdt_serial_uart8250;
>>> extern struct fdt_serial fdt_serial_sifive;
>>> +extern struct fdt_serial fdt_serial_litex;
>>> extern struct fdt_serial fdt_serial_htif;
>>> extern struct fdt_serial fdt_serial_shakti;
>>> extern struct fdt_serial fdt_serial_gaisler;
>>> @@ -22,6 +23,7 @@ extern struct fdt_serial fdt_serial_gaisler;
>>> static struct fdt_serial *serial_drivers[] = {
>>> &fdt_serial_uart8250,
>>> &fdt_serial_sifive,
>>> + &fdt_serial_litex,
>>> &fdt_serial_htif,
>>> &fdt_serial_shakti,
>>> &fdt_serial_gaisler
>>> diff --git a/lib/utils/serial/fdt_serial_litex.c b/lib/utils/serial/fdt_serial_litex.c
>>> new file mode 100644
>>> index 0000000..0fa5777
>>> --- /dev/null
>>> +++ b/lib/utils/serial/fdt_serial_litex.c
>>> @@ -0,0 +1,35 @@
>>> +/*
>>> + * SPDX-License-Identifier: BSD-2-Clause
>>> + *
>>> + * Copyright (c) 2021 Gabriel Somlo
>>> + *
>>> + * Authors:
>>> + * Gabriel Somlo <gsomlo at gmail.com>
>>> + */
>>> +
>>> +#include <sbi_utils/fdt/fdt_helper.h>
>>> +#include <sbi_utils/serial/fdt_serial.h>
>>> +#include <sbi_utils/serial/litex-uart.h>
>>> +
>>> +static int serial_litex_init(void *fdt, int nodeoff,
>>> + const struct fdt_match *match)
>>> +{
>>> + int rc;
>>> + struct platform_uart_data uart;
>>> +
>>> + rc = fdt_parse_litex_uart_node(fdt, nodeoff, &uart);
>>> + if (rc)
>>> + return rc;
>>> +
>>> + return litex_uart_init(uart.addr);
>>> +}
>>> +
>>> +static const struct fdt_match serial_litex_match[] = {
>>> + { .compatible = "litex,liteuart" },
>>> + { },
>>> +};
>>> +
>>> +struct fdt_serial fdt_serial_litex = {
>>> + .match_table = serial_litex_match,
>>> + .init = serial_litex_init
>>> +};
>>> diff --git a/lib/utils/serial/litex-uart.c b/lib/utils/serial/litex-uart.c
>>> new file mode 100644
>>> index 0000000..e35fbe8
>>> --- /dev/null
>>> +++ b/lib/utils/serial/litex-uart.c
>>> @@ -0,0 +1,62 @@
>>> +/*
>>> + * SPDX-License-Identifier: BSD-2-Clause
>>> + *
>>> + * Copyright (c) 2021 Gabriel Somlo
>>> + *
>>> + * Authors:
>>> + * Gabriel Somlo <gsomlo at gmail.com>
>>> + */
>>> +
>>> +#include <sbi/riscv_io.h>
>>> +#include <sbi/sbi_console.h>
>>> +#include <sbi_utils/serial/litex-uart.h>
>>> +
>>> +/* clang-format off */
>>> +
>>> +#define UART_REG_RXTX 0
>>> +#define UART_REG_TXFULL 1
>>> +#define UART_REG_RXEMPTY 2
>>> +#define UART_REG_EV_STATUS 3
>>> +#define UART_REG_EV_PENDING 4
>>> +#define UART_REG_EV_ENABLE 5
>>> +
>>> +/* clang-format on */
>>> +
>>> +static volatile u32 *uart_base;
>>> +
>>> +static u8 get_reg(u8 reg)
>>> +{
>>> + return readb(uart_base + reg);
>>> +}
>>> +
>>> +static void set_reg(u8 reg, u8 val)
>>> +{
>>> + writeb(val, uart_base + reg);
>>> +}
>>> +
>>> +static void litex_uart_putc(char ch)
>>> +{
>>> + while (get_reg(UART_REG_TXFULL));
>>> + set_reg(UART_REG_RXTX, ch);
>>> +}
>>> +
>>> +static int litex_uart_getc(void)
>>> +{
>> We should wait here before reading
>
> Wait for what condition, and/or for how long?
>
> Are you perhaps referring to your recently submitted patch at
> https://lists.infradead.org/pipermail/opensbi/2021-November/002174.html ?
> (where you suggest we should loop or block until a character becomes
> available, instead of returning -1)?
>
> If that's the case, I should probably wait until your patch is applied
> upstream (hopefully soon :) ), before re-submitting a v4 of LiteX UART
> with similar modifications.
>
> Otherwise, please clarify.
Ignore that patch, it’s a bad idea and breaks things.
Jess
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