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dfd37668ea
Fixed behaviour of get_mctrl() serial driver function as documented in: https://www.kernel.org/doc/Documentation/serial/driver Added device-tree properties 'dcd-override', 'dsr-override', 'cts-override', and 'ri-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@broadcom.com> Signed-off-by: Jonathan Richardson <jonathar@broadcom.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
74 lines
2.4 KiB
Plaintext
74 lines
2.4 KiB
Plaintext
* Synopsys DesignWare ABP UART
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Required properties:
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- compatible : "snps,dw-apb-uart"
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- reg : offset and length of the register set for the device.
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- interrupts : should contain uart interrupt.
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Clock handling:
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The clock rate of the input clock needs to be supplied by one of
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- clock-frequency : the input clock frequency for the UART.
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- clocks : phandle to the input clock
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The supplying peripheral clock can also be handled, needing a second property
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- clock-names: tuple listing input clock names.
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Required elements: "baudclk", "apb_pclk"
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Optional properties:
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- resets : phandle to the parent reset controller.
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- reg-shift : quantity to shift the register offsets by. If this property is
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not present then the register offsets are not shifted.
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- reg-io-width : the size (in bytes) of the IO accesses that should be
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performed on the device. If this property is not present then single byte
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accesses are used.
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- dcd-override : Override the DCD modem status signal. This signal will always
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be reported as active instead of being obtained from the modem status
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register. Define this if your serial port does not use this pin.
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- dsr-override : Override the DTS modem status signal. This signal will always
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be reported as active instead of being obtained from the modem status
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register. Define this if your serial port does not use this pin.
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- cts-override : Override the CTS modem status signal. This signal will always
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be reported as active instead of being obtained from the modem status
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register. Define this if your serial port does not use this pin.
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- ri-override : Override the RI modem status signal. This signal will always be
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reported as inactive instead of being obtained from the modem status register.
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Define this if your serial port does not use this pin.
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Example:
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uart@80230000 {
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compatible = "snps,dw-apb-uart";
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reg = <0x80230000 0x100>;
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clock-frequency = <3686400>;
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interrupts = <10>;
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reg-shift = <2>;
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reg-io-width = <4>;
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dcd-override;
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dsr-override;
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cts-override;
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ri-override;
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};
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Example with one clock:
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uart@80230000 {
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compatible = "snps,dw-apb-uart";
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reg = <0x80230000 0x100>;
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clocks = <&baudclk>;
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interrupts = <10>;
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reg-shift = <2>;
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reg-io-width = <4>;
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};
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Example with two clocks:
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uart@80230000 {
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compatible = "snps,dw-apb-uart";
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reg = <0x80230000 0x100>;
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clocks = <&baudclk>, <&apb_pclk>;
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clock-names = "baudclk", "apb_pclk";
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interrupts = <10>;
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reg-shift = <2>;
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reg-io-width = <4>;
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};
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