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[222.224.229.1]) by smtp.gmail.com with ESMTPSA id z16sm10746737pjq.42.2021.05.15.01.45.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 15 May 2021 01:45:39 -0700 (PDT) From: Stafford Horne To: LKML Cc: Stafford Horne , Florent Kermarrec , Mateusz Holenko , Joel Stanley , "Gabriel L . Somlo" , Jonathan Corbet , Greg Kroah-Hartman , Jiri Slaby , Karol Gugala , "Paul E. McKenney" , Randy Dunlap , Andrew Morton , Thomas Gleixner , Viresh Kumar , Mike Kravetz , Peter Zijlstra , linux-doc@vger.kernel.org, linux-serial@vger.kernel.org Subject: [PATCH] serial/liteuart; Add support for earlycon Date: Sat, 15 May 2021 17:45:18 +0900 Message-Id: <20210515084519.167343-1-shorne@gmail.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Most litex boards using RISC-V soft cores us the sbi earlycon, however this is not available for non RISC-V litex SoC. This patch enables earlycon for liteuart which is available on all Litex SoC's making support for earycon debugging more widely available. Signed-off-by: Stafford Horne Cc: Florent Kermarrec Cc: Mateusz Holenko Cc: Joel Stanley Cc: Gabriel L. Somlo --- .../admin-guide/kernel-parameters.txt | 5 +++ drivers/tty/serial/Kconfig | 1 + drivers/tty/serial/liteuart.c | 31 +++++++++++++++++++ 3 files changed, 37 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 04545725f187..2d4a43af8de2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1084,6 +1084,11 @@ the driver will use only 32-bit accessors to read/write the device registers. + liteuart, + Start an early console on a litex serial port at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + meson, Start an early, polled-mode console on a meson serial port at the specified address. The serial port must diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig index 0c4cd4a348f4..9ceffe6ab6fd 100644 --- a/drivers/tty/serial/Kconfig +++ b/drivers/tty/serial/Kconfig @@ -1531,6 +1531,7 @@ config SERIAL_LITEUART depends on OF || COMPILE_TEST depends on LITEX select SERIAL_CORE + select SERIAL_EARLYCON help This driver is for the FPGA-based LiteUART serial controller from LiteX SoC builder. diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c index 64842f3539e1..38c472487e68 100644 --- a/drivers/tty/serial/liteuart.c +++ b/drivers/tty/serial/liteuart.c @@ -372,6 +372,37 @@ static int __init liteuart_console_init(void) console_initcall(liteuart_console_init); #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */ +#ifdef CONFIG_SERIAL_EARLYCON +static void early_liteuart_putc(struct uart_port *port, int c) +{ + while (litex_read8(port->membase + OFF_TXFULL)) + cpu_relax(); + + litex_write8(port->membase + OFF_RXTX, c); +} + +static void early_liteuart_write(struct console *console, const char *s, + unsigned int count) +{ + struct earlycon_device *device = console->data; + struct uart_port *port = &device->port; + + uart_console_write(port, s, count, early_liteuart_putc); +} + +static int __init early_liteuart_setup(struct earlycon_device *device, + const char *options) +{ + if (!device->port.membase) + return -ENODEV; + + device->con->write = early_liteuart_write; + return 0; +} + +OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup); +#endif /* CONFIG_SERIAL_EARLYCON */ + static int __init liteuart_init(void) { int res;