From cbf9172eb657d36140188acf55238cd630cd0f3c Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Fri, 29 Apr 2022 21:40:18 +0100 Subject: [PATCH] serial: sifive: Report actual baud base rather than fixed 115200 [ Upstream commit 0a7ff843d507ce2cca2c3b7e169ee56e28133530 ] The base baud value reported is supposed to be the highest baud rate that can be set for a serial port. The SiFive FU740-C000 SOC's on-chip UART supports baud rates of up to 1/16 of the input clock rate, which is the bus clock `tlclk'[1], often at 130MHz in the case of the HiFive Unmatched board. However the sifive UART driver reports a fixed value of 115200 instead: 10010000.serial: ttySIF0 at MMIO 0x10010000 (irq = 1, base_baud = 115200) is a SiFive UART v0 10011000.serial: ttySIF1 at MMIO 0x10011000 (irq = 2, base_baud = 115200) is a SiFive UART v0 even though we already support setting higher baud rates, e.g.: $ tty /dev/ttySIF1 $ stty speed 230400 The baud base value is computed by the serial core by dividing the UART clock recorded in `struct uart_port' by 16, which is also the minimum value of the clock divider supported, so correct the baud base value reported by setting the UART clock recorded to the input clock rate rather than 115200: 10010000.serial: ttySIF0 at MMIO 0x10010000 (irq = 1, base_baud = 8125000) is a SiFive UART v0 10011000.serial: ttySIF1 at MMIO 0x10011000 (irq = 2, base_baud = 8125000) is a SiFive UART v0 References: [1] "SiFive FU740-C000 Manual", v1p3, SiFive, Inc., August 13, 2021, Section 16.9 "Baud Rate Divisor Register (div)", pp.143-144 Signed-off-by: Maciej W. Rozycki Fixes: 1f1496a923b6 ("riscv: Fix sifive serial driver") Link: https://lore.kernel.org/r/alpine.DEB.2.21.2204291656280.9383@angie.orcam.me.uk Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/sifive.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c index 0ac0371f943b6..a579d46ed78c5 100644 --- a/drivers/tty/serial/sifive.c +++ b/drivers/tty/serial/sifive.c @@ -998,7 +998,7 @@ static int sifive_serial_probe(struct platform_device *pdev) /* Set up clock divider */ ssp->clkin_rate = clk_get_rate(ssp->clk); ssp->baud_rate = SIFIVE_DEFAULT_BAUD_RATE; - ssp->port.uartclk = ssp->baud_rate * 16; + ssp->port.uartclk = ssp->clkin_rate; __ssp_update_div(ssp); platform_set_drvdata(pdev, ssp);