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Subject: [PATCH V5 2/2] virtio-gpio: Add support for interrupts
This patch adds support for interrupts to the virtio-gpio specification.
This uses the feature bit 0 for the same.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
virtio-gpio.tex | 153 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 150 insertions(+), 3 deletions(-)
diff --git a/virtio-gpio.tex b/virtio-gpio.tex
index 40020620d714..56e0bde4d986 100644
--- a/virtio-gpio.tex
+++ b/virtio-gpio.tex
@@ -20,7 +20,9 @@ \subsection{Virtqueues}\label{sec:Device Types / GPIO Device / Virtqueues}
\subsection{Feature bits}\label{sec:Device Types / GPIO Device / Feature bits}
-None currently defined.
+\begin{description}
+\item[VIRTIO_GPIO_F_IRQ (0)] The device supports interrupts on GPIO lines.
+\end{description}
\subsection{Device configuration layout}\label{sec:Device Types / GPIO Device / Device configuration layout}
@@ -79,6 +81,12 @@ \subsection{Device Initialization}\label{sec:Device Types / GPIO Device / Device
\item The driver MUST populate the \field{rxq} virtqueue with \field{struct
virtio_gpio_msg} buffer.
+
+\item The driver MUST check the presence of \field{VIRTIO_GPIO_F_IRQ} feature
+ before initiating any IRQ messages.
+
+\item The device MUST mask interrupts on all the GPIO lines, if the
+ \field{VIRTIO_GPIO_F_IRQ} feature is supported.
\end{itemize}
\subsection{Device Operation}\label{sec:Device Types / GPIO Device / Device Operation}
@@ -111,8 +119,12 @@ \subsection{Device Operation}\label{sec:Device Types / GPIO Device / Device Oper
with VIRTIO_GPIO_MSG_RESPONSE mask and updating the \field{value} field based on
message type.
-For the current version of the specification, the sender is always the driver
-and receiver is always the device.
+The device is the sender only for the messages of type
+\field{VIRTIO_GPIO_MSG_IRQ_EVENT} and the device sends it over the \field{rxq}
+virtqueue.
+
+The driver is the sender for all other message types and send them over
+\field{txq} virtqueue.
\begin{lstlisting}
/* GPIO message types: driver -> device */
@@ -123,11 +135,27 @@ \subsection{Device Operation}\label{sec:Device Types / GPIO Device / Device Oper
#define VIRTIO_GPIO_MSG_SET_DIRECTION_OUT 0x0005
#define VIRTIO_GPIO_MSG_GET_VALUE 0x0006
#define VIRTIO_GPIO_MSG_SET_VALUE 0x0007
+#define VIRTIO_GPIO_MSG_IRQ_TYPE 0x0008
+#define VIRTIO_GPIO_MSG_IRQ_MASK 0x0009
+#define VIRTIO_GPIO_MSG_IRQ_UNMASK 0x000a
+
+/* GPIO message type: from device -> driver */
+#define VIRTIO_GPIO_MSG_IRQ_EVENT 0x000b
/* GPIO response mask, to be Or'ed with one of the above */
#define VIRTIO_GPIO_MSG_RESPONSE 0x8000
\end{lstlisting}
+\begin{lstlisting}
+/* GPIO interrupt type */
+#define VIRTIO_GPIO_IRQ_TYPE_NONE 0x00
+#define VIRTIO_GPIO_IRQ_TYPE_EDGE_RISING 0x01
+#define VIRTIO_GPIO_IRQ_TYPE_EDGE_FALLING 0x02
+#define VIRTIO_GPIO_IRQ_TYPE_EDGE_BOTH 0x03
+#define VIRTIO_GPIO_IRQ_TYPE_LEVEL_HIGH 0x04
+#define VIRTIO_GPIO_IRQ_TYPE_LEVEL_LOW 0x08
+\end{lstlisting}
+
The response messages may contain error codes (in the \field{value} field) on
failures, they must be read as negative POSIX errno codes, unless stated
otherwise, i.e. 0 as success, and negative value as POSIX error code, positive
@@ -238,6 +266,81 @@ \subsubsection{Device Operation: Set Value}\label{sec:Device Types / GPIO Device
\hline
\end{tabular}
+\subsubsection{Device Operation: IRQ Type}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Type }
+
+The driver initiates this message to request the device to set the IRQ trigger
+type to one of the \field{VIRTIO_GPIO_IRQ_TYPE_*} values, for a line configured
+for input.
+
+This request is only allowed if the \field{VIRTIO_GPIO_F_IRQ} feature is
+supported by the device.
+
+\begin{tabular}{ |l||l|l|l| }
+\hline
+Fields & \field{type} & \field{gpio} & \field{value} \\
+\hline
+Message & \field{VIRTIO_GPIO_MSG_IRQ_TYPE} & line number & one of \field{VIRTIO_GPIO_IRQ_TYPE_*} \\
+\hline
+Response & \field{VIRTIO_GPIO_MSG_IRQ_TYPE} \newline | \field{VIRTIO_GPIO_MSG_RESPONSE} & line number & 0 = success, \newline or -errno = failure \\
+\hline
+\end{tabular}
+
+\subsubsection{Device Operation: IRQ Mask}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Mask }
+
+The driver initiates this message to request the device to mask IRQ on a GPIO
+line configured for input.
+
+This request is only allowed if the \field{VIRTIO_GPIO_F_IRQ} feature is
+supported by the device.
+
+\begin{tabular}{ |l||l|l|l| }
+\hline
+Fields & \field{type} & \field{gpio} & \field{value} \\
+\hline
+Message & \field{VIRTIO_GPIO_MSG_IRQ_MASK} & line number & 0 \\
+\hline
+Response & \field{VIRTIO_GPIO_MSG_IRQ_MASK} \newline | \field{VIRTIO_GPIO_MSG_RESPONSE} & line number & 0 = success, \newline or -errno = failure \\
+\hline
+\end{tabular}
+
+\subsubsection{Device Operation: IRQ Unmask}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Unmask }
+
+The driver initiates this message to request the device to unmask IRQ on a GPIO
+line configured for input.
+
+This request is only allowed if the \field{VIRTIO_GPIO_F_IRQ} feature is
+supported by the device.
+
+\begin{tabular}{ |l||l|l|l| }
+\hline
+Fields & \field{type} & \field{gpio} & \field{value} \\
+\hline
+Message & \field{VIRTIO_GPIO_MSG_IRQ_UNMASK} & line number & 0 \\
+\hline
+Response & \field{VIRTIO_GPIO_MSG_IRQ_UNMASK} \newline | \field{VIRTIO_GPIO_MSG_RESPONSE} & line number & 0 = success, \newline or -errno = failure \\
+\hline
+\end{tabular}
+
+\subsubsection{Device Operation: IRQ Event}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Event }
+
+The device initiates this message to notify the driver of an IRQ event on a line
+previously configured for interrupt.
+
+This request is only allowed if the \field{VIRTIO_GPIO_F_IRQ} feature is
+supported by the device.
+
+This is the only message which is initiated by the device and not the driver.
+
+\begin{tabular}{ |l||l|l|l| }
+\hline
+Fields & \field{type} & \field{gpio} & \field{value} \\
+\hline
+Message & \field{VIRTIO_GPIO_MSG_IRQ_EVENT} & line number & 0 \\
+\hline
+Response & \field{VIRTIO_GPIO_MSG_IRQ_EVENT} \newline | \field{VIRTIO_GPIO_MSG_RESPONSE} & line number & 0 = success, \newline or -errno = failure \\
+\hline
+\end{tabular}
+
\drivernormative{\subsubsection}{Device Operation}{Device Types / GPIO Device / Device Operation}
\begin{itemize}
@@ -252,6 +355,11 @@ \subsubsection{Device Operation: Set Value}\label{sec:Device Types / GPIO Device
\item The driver MUST NOT initiate another message for a GPIO line, before
response to the previously sent message is received for the same line.
+
+\item The driver MUST NOT send IRQ messages for a GPIO line configured for output.
+
+\item The driver MUST NOT initiate IRQ messages if the \field{VIRTIO_GPIO_F_IRQ}
+ feature is not supported by the device.
\end{itemize}
\devicenormative{\subsubsection}{Device Operation}{Device Types / GPIO Device / Device Operation}
@@ -315,3 +423,42 @@ \subsubsection{Driver Requests}\label{sec:Device Types / GPIO Device / Message F
\item The driver can initiate an request for a different GPIO line before
receiving response for a previous request for another line.
\end{itemize}
+
+\subsubsection{Device Interrupts}\label{sec:Device Types / GPIO Device / Message Flow / Interrupts}
+
+The \field{VIRTIO_GPIO_MSG_IRQ_EVENT} message type can only be initiated by the
+device and sent to the driver over the \field{rxq} virtqueue.
+
+\begin{itemize}
+\item The device, on sensing an interrupt for a GPIO line, prepares a buffer of
+ type \field{struct virtio_gpio_msg} and sets its \field{type} to
+ \field{VIRTIO_GPIO_MSG_IRQ_EVENT}, \field{gpio} field with a GPIO line
+ number, and \field{value} field to 0.
+
+\item The device sends the buffer to the driver over the \field{rxq} virtqueue.
+
+\item The device MUST NOT initiate another interrupt request for the same GPIO
+ line before receiving a response from the driver.
+
+\item The driver, after receiving the buffer from the driver, handles the
+ interrupt.
+
+\item The driver at this point may initiate a new request (like masking of the
+ IRQ line) and send it over to the device over the \field{txq} virtqueue.
+ The device must respond to them, without waiting for a response to the
+ IRQ itself.
+
+\item The driver prepares a buffer of type \field{struct virtio_gpio_msg} and
+ sets its \field{type} field to (\field{VIRTIO_GPIO_MSG_IRQ_EVENT} |
+ \field{VIRTIO_GPIO_MSG_RESPONSE}), \field{gpio} field with \field{gpio} of
+ the received buffer, and \field{value} to message defined value.
+
+\item The driver sends the buffer to the device over the \field{txq} virtqueue.
+
+\item The device receives and processes the buffer.
+
+\item The device can initiate another IRQ request for the same GPIO line now.
+
+\item The driver can initiate an IRQ request for a different GPIO line before
+ receiving response for a previous IRQ request for another line.
+\end{itemize}
--
2.31.1.272.g89b43f80a514
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