Fixed behaviour of get_mctrl() serial driver function as documented in: https://www.kernel.org/doc/Documentation/serial/driver Added device-tree property 'msr-override' specific to the Synopsis 8250 DesignWare UART driver. Allows one to force Data Carrier Detect, Clear To Send, and Data Set Ready signals to permanently be reported as active. The Ring indicator can be forced to be reported as inactive. It is possible that if modem control signalling is enabled on a port that doesn't have these pins (e.g. - a simple two wire Tx/Rx port), the driver can hang indefinitely waiting for the state to change. The new DT properties allow the driver to ignore the state of these pins on serial ports that don't support them, as recommended in the kernel documentation. Reviewed-by: JD (Jiandong) Zheng <jdzheng@xxxxxxxxxxxx> Reviewed-by: Jonathan Richardson <jonathar@xxxxxxxxxxxx> Reviewed-by: Scott Branden <sbranden@xxxxxxxxxxxx> Tested-by: Scott Branden <sbranden@xxxxxxxxxxxx> Tested-by: Jonathan Richardson <jonathar@xxxxxxxxxxxx> Signed-off-by: Jonathan Richardson <jonathar@xxxxxxxxxxxx> --- .../bindings/serial/snps-dw-apb-uart.txt | 7 ++++ drivers/tty/serial/8250/8250_dw.c | 41 ++++++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt index 7f76214..010e52b 100644 --- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt +++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt @@ -21,6 +21,12 @@ Optional properties: - reg-io-width : the size (in bytes) of the IO accesses that should be performed on the device. If this property is not present then single byte accesses are used. +- msr-override : array of strings to be used to override the individual + modem status signals for DCD, DSR, CTS, and RI. If the property is not + present, the individual signals are obtained from the modem status register. + Strings accepted are "dcd", "dsr", "cts", and "ri". If "dcd", "dsr", or + "cts" are present, these signals will always be reported as active. If + "ri" is present, this signal will always be reported as inactive. Example: @@ -31,6 +37,7 @@ Example: interrupts = <10>; reg-shift = <2>; reg-io-width = <4>; + msr-override = "dcd", "dsr", cts", "ri" }; Example with one clock: diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 555de07..06dc873 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -59,6 +59,8 @@ struct dw8250_data { u8 usr_reg; int last_mcr; int line; + int msr_mask_on; + int msr_mask_off; struct clk *clk; struct clk *pclk; struct reset_control *rst; @@ -81,6 +83,12 @@ static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value) value &= ~UART_MSR_DCTS; } + /* Override any modem control signals if needed */ + if (offset == UART_MSR) { + value |= d->msr_mask_on; + value &= ~d->msr_mask_off; + } + return value; } @@ -290,6 +298,8 @@ static int dw8250_probe_of(struct uart_port *p, u32 val; bool has_ucv = true; int id; + int msr_cnt, i; + const char *inp_name; #ifdef CONFIG_64BIT if (of_device_is_compatible(np, "cavium,octeon-3860-uart")) { @@ -334,6 +344,37 @@ static int dw8250_probe_of(struct uart_port *p, if (id >= 0) p->line = id; + msr_cnt = of_property_count_strings(np, "msr-override"); + + if (msr_cnt > 0) { + for (i = 0; i < msr_cnt; i++) { + of_property_read_string_index(np, "msr-override", i, + &inp_name); + + if (!strcmp("dcd", inp_name)) { + /* Always report DCD as active */ + data->msr_mask_on |= UART_MSR_DCD; + data->msr_mask_off |= UART_MSR_DDCD; + } else if (!strcmp("dsr", inp_name)) { + /* Always report DSR as active */ + data->msr_mask_on |= UART_MSR_DSR; + data->msr_mask_off |= UART_MSR_DDSR; + } else if (!strcmp("cts", inp_name)) { + /* Always report CTS as active */ + data->msr_mask_on |= UART_MSR_CTS; + data->msr_mask_off |= UART_MSR_DCTS; + } else if (!strcmp("ri", inp_name)) { + /* Always report Ring indicator as inactive */ + data->msr_mask_off |= UART_MSR_RI; + data->msr_mask_off |= UART_MSR_TERI; + } else { + dev_err(p->dev, + "Ignore unknown msr-override %s\n", + inp_name); + } + } + } + /* clock got configured through clk api, all done */ if (p->uartclk) return 0; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
