This patch adds support for interrupts to the virtio-gpio specification. This uses the feature bit 0 for the same.
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/114 Cc: Marc Zyngier maz@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Reviewed-by: Linus Walleij linus.walleij@linaro.org Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- V8 -> V9: - The patch for base GPIO specification is already merged, sending this separately now.
- Differentiate properly between enabling/disabling and masking/unmasking of the interrupt.
- Specify how a trigger type should be changed, i.e. by disabling interrupt first.
- No fixed sequence for enabling/unmasking of the interrupt, any of them can be done first. The interrupt is only delivered once it is enabled and unmasked.
- Use normative text only in normative sections.
- Guest side Linux driver's IRQ implementation:
https://lore.kernel.org/linux-gpio/96223fb8143a4eaa9b183d376ff46e5cd8ef54b4....
conformance.tex | 2 + virtio-gpio.tex | 248 +++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 249 insertions(+), 1 deletion(-)
diff --git a/conformance.tex b/conformance.tex index c52f1a40be2d..64bcc12d1199 100644 --- a/conformance.tex +++ b/conformance.tex @@ -310,6 +310,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
\begin{itemize} \item \ref{drivernormative:Device Types / GPIO Device / requestq Operation} +\item \ref{drivernormative:Device Types / GPIO Device / eventq Operation} \end{itemize}
\conformance{\section}{Device Conformance}\label{sec:Conformance / Device Conformance} @@ -568,6 +569,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
\begin{itemize} \item \ref{devicenormative:Device Types / GPIO Device / requestq Operation} +\item \ref{devicenormative:Device Types / GPIO Device / eventq Operation} \end{itemize}
\conformance{\section}{Legacy Interface: Transitional Device and Transitional Driver Conformance}\label{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance} diff --git a/virtio-gpio.tex b/virtio-gpio.tex index 3c614ec97b92..fba7ec400bb3 100644 --- a/virtio-gpio.tex +++ b/virtio-gpio.tex @@ -11,11 +11,17 @@ \subsection{Virtqueues}\label{sec:Device Types / GPIO Device / Virtqueues}
\begin{description} \item[0] requestq +\item[1] eventq \end{description}
+The \field{eventq} virtqueue is available only if the \field{VIRTIO_GPIO_F_IRQ} +feature is enabled by the device. + \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}
@@ -46,6 +52,14 @@ \subsection{Device Initialization}\label{sec:Device Types / GPIO Device / Device
\begin{itemize} \item The driver configures and initializes the \field{requestq} virtqueue. + +\item The driver checks the presence of \field{VIRTIO_GPIO_F_IRQ} feature + before initiating any IRQ related messages. + +\item The driver configures and initializes the \field{eventq} virtqueue. + +\item The device configures all GPIO lines in \field{VIRTIO_GPIO_IRQ_TYPE_NONE} + trigger type state. \end{itemize}
\subsection{Device Operation: requestq}\label{sec:Device Types / GPIO Device / requestq Operation} @@ -105,11 +119,20 @@ \subsection{Device Operation: requestq}\label{sec:Device Types / GPIO Device / r #define VIRTIO_GPIO_MSG_SET_DIRECTION 0x0003 #define VIRTIO_GPIO_MSG_GET_VALUE 0x0004 #define VIRTIO_GPIO_MSG_SET_VALUE 0x0005 +#define VIRTIO_GPIO_MSG_SET_IRQ_TYPE 0x0006
/* GPIO Direction types */ #define VIRTIO_GPIO_DIRECTION_NONE 0x00 #define VIRTIO_GPIO_DIRECTION_OUT 0x01 #define VIRTIO_GPIO_DIRECTION_IN 0x02 + +/* GPIO interrupt types */ +#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}
\subsubsection{requestq Operation: Get Line Names}\label{sec:Device Types / GPIO Device / requestq Operation / Get Line Names} @@ -270,6 +293,74 @@ \subsubsection{requestq Operation: Set Value}\label{sec:Device Types / GPIO Devi \hline \end{tabularx}
+\subsubsection{requestq Operation: Set IRQ Type}\label{sec:Device Types / GPIO Device / requestq Operation / Set IRQ Type} + +This request is allowed only if the \field{VIRTIO_GPIO_F_IRQ} feature is enabled +by the device. + +The interrupt configuration is divided into two steps, enabling or disabling of +the interrupt at the device and masking or unmasking of the interrupt for +delivery at the driver. This request only pertains to enabling or disabling of +the interrupt at the device, the masking and unmasking of the interrupt is +handled by a separate request that takes place over the \field{eventq} +virtqueue. + +The driver sends the \field{VIRTIO_GPIO_MSG_SET_IRQ_TYPE} message over the +\field{requestq} virtqueue to enable or disable interrupt for a GPIO line at +the device. + +The driver sends this message with trigger type set to any valid value other +than \field{VIRTIO_GPIO_IRQ_TYPE_NONE}, to enable the interrupt for a GPIO line, +this doesn't unmask the interrupt for delivery at the driver though. For edge +trigger type, the device should latch the interrupt events from this point +onward and notify it to the driver once the interrupt is unmasked. For level +trigger type, the device should notify the driver once the interrupt signal on a +line is sensed and the interrupt is unmasked for the line. + +The driver sends this message with trigger type set to +\field{VIRTIO_GPIO_IRQ_TYPE_NONE}, to disable the interrupt for a GPIO line. The +device should discard any latched interrupt event associated with it. In order +to change the trigger type of an already enabled interrupt, the driver should +first disable the interrupt and then re-enable it with appropriate trigger type. + +The interrupts are masked at initialization and the driver unmasks them by +queuing a pair of buffers, of type \field{virtio_gpio_irq_request} and +\field{virtio_gpio_irq_response}, over the \field{eventq} virtqueue for a GPIO +line. A separate pair of buffers must be queued for each GPIO line, the driver +wants to configure for interrupts. Once the interrupt is unmasked by the driver +and the interrupt is also enabled at the device, the device can notify the +driver of an active interrupt signal on the GPIO line. This is done by updating +the \field{struct virtio_gpio_irq_response} buffer's \field{status} with +\field{VIRTIO_GPIO_IRQ_STATUS_VALID} and returning the updated buffers to the +driver. The interrupt is masked automatically at this point until the buffers +are available again at the device. + +When the interrupt is disabled by the driver, by setting the trigger type to +\field{VIRTIO_GPIO_IRQ_TYPE_NONE}, the device should return any unused pair of +buffers for the GPIO line, over the \field{eventq} virtqueue, after setting the +\field{status} field to \field{VIRTIO_GPIO_IRQ_STATUS_INVALID}. This also masks +the interrupt. + +The driver can enable and unmask the interrupt in any order, i.e. it can enable +the interrupt first and then queue the buffers or queue the buffers first and +then enable the interrupt. + +\begin{tabularx}{\textwidth}{ |l||X|X|X| } +\hline +\textbf{Request} & \field{type} & \field{gpio} & \field{value} \ +\hline +& \field{VIRTIO_GPIO_MSG_SET_IRQ_TYPE} & line number & one of \field{VIRTIO_GPIO_IRQ_TYPE_*} \ +\hline +\end{tabularx} + +\begin{tabularx}{\textwidth}{ |l||X|X| } +\hline +\textbf{Response} & \field{status} & \field{value} \ +\hline +& \field{VIRTIO_GPIO_STATUS_*} & 0 \ +\hline +\end{tabularx} + \subsubsection{requestq Operation: Message Flow}\label{sec:Device Types / GPIO Device / requestq Operation / Message Flow}
\begin{itemize} @@ -313,6 +404,20 @@ \subsubsection{requestq Operation: Message Flow}\label{sec:Device Types / GPIO D
\item The driver MAY send multiple messages for same or different GPIO lines in parallel. + +\item The driver MUST NOT send IRQ messages if the \field{VIRTIO_GPIO_F_IRQ} + feature is not enabled by the device. + +\item The driver MUST NOT send IRQ messages for a GPIO line configured for + output. + +\item The driver MUST set the IRQ trigger type to + \field{VIRTIO_GPIO_IRQ_TYPE_NONE} once it is done using the GPIO line + configured for interrupts. + +\item In order to change the trigger type of an already enabled interrupt, the + driver MUST first disable the interrupt and then re-enable it with + appropriate trigger type. \end{itemize}
\devicenormative{\subsubsection}{requestq Operation}{Device Types / GPIO Device / requestq Operation} @@ -344,4 +449,145 @@ \subsubsection{requestq Operation: Message Flow}\label{sec:Device Types / GPIO D \item The device MUST discard all state information corresponding to a GPIO line, once the driver has requested to set its direction to \field{VIRTIO_GPIO_DIRECTION_NONE}. + +\item The device MUST latch an edge interrupt if the interrupt is enabled but + still masked. + +\item The device MUST NOT latch an level interrupt if the interrupt is enabled + but still masked. + +\item The device MUST discard any latched interrupt for a GPIO line, once + interrupt is disabled for the same. +\end{itemize} + +\subsection{Device Operation: eventq}\label{sec:Device Types / GPIO Device / eventq Operation} + +The \field{eventq} virtqueue is used by the driver to unmask the interrupts and +used by the device to notify the driver of newly sensed interrupts. In order to +unmask interrupt on a GPIO line, the driver queues a pair of buffers, +\field{struct virtio_gpio_irq_request} (filled by driver) and \field{struct +virtio_gpio_irq_response} (to be filled by device later), to the \field{eventq} +virtqueue. A separate pair of buffers must be queued for each GPIO line, the +driver wants to configure for interrupts. The device, on sensing an interrupt, +returns the pair of buffers for the respective GPIO line, which also masks the +interrupts. The driver can queue the buffers again to unmask the interrupt. + +\begin{lstlisting} +struct virtio_gpio_irq_request { + le16 gpio; +}; +\end{lstlisting} + +This structure is filled by the driver and read by the device. + +\begin{description} +\item[\field{gpio}] is the GPIO line number, i.e. 0 <= \field{gpio} < + \field{ngpio}. +\end{description} + +\begin{lstlisting} +struct virtio_gpio_irq_response { + u8 status; +}; + +/* Possible values of the interrupt status field */ +#define VIRTIO_GPIO_IRQ_STATUS_INVALID 0x0 +#define VIRTIO_GPIO_IRQ_STATUS_VALID 0x1 +\end{lstlisting} + +This structure is filled by the device and read by the driver. + +\begin{description} +\item[\field{status}] of the interrupt event, + \field{VIRTIO_GPIO_IRQ_STATUS_VALID} on interrupt and + \field{VIRTIO_GPIO_IRQ_STATUS_INVALID} to return the buffers back to the + driver after interrupt is disabled. +\end{description} + +\subsubsection{eventq Operation: Message Flow}\label{sec:Device Types / GPIO Device / eventq Operation / Message Flow} + +\begin{itemize} +\item The virtio-gpio driver is requested by a client driver to enable interrupt + for a GPIO line and configure it to a particular trigger type. + +\item The driver sends the \field{VIRTIO_GPIO_MSG_SET_IRQ_TYPE} message, over + the \field{requestq} virtqueue, and the device configures the GPIO line for + the requested trigger type and enables the interrupt. The interrupt is still + masked for delivery though. The device shall latch the interrupt from now + onward for edge trigger type. + +\item The driver unmasks the interrupt by queuing a pair of buffers to the + \field{eventq} virtqueue for the GPIO line. The driver can do this before + enabling the interrupt as well, though the interrupt must be both unmasked + and enabled to get delivered at the driver. + +\item The driver notifies the device of the presence of new buffers on the + \field{eventq} virtqueue. The interrupt is fully configured at this point. + +\item The device, on sensing an active interrupt on the GPIO line, finds the + matching buffers (based on GPIO line number) from the \field{eventq} + virtqueue and update its \field{struct virtio_gpio_irq_response} buffer's + \field{status} with \field{VIRTIO_GPIO_IRQ_STATUS_VALID} and returns the + pair of buffers to the device. This results in masking the interrupt as + well. + +\item The device notifies the driver of the presence of returned buffers on the + \field{eventq} virtqueue. + +\item If the GPIO line is configured for level interrupts, the device ignores + any further interrupt signals on this GPIO line, until the interrupt is + unmasked again by the driver by making the buffers available to the device. + Once the interrupt is unmasked again and the interrupt on the line is still + active, the device shall notify the driver again. + +\item If the GPIO line is configured for edge interrupts, the device latches + the interrupt received for this GPIO line, until the interrupt is unmasked + again by the driver by making the buffers available to the device. Once the + interrupt is unmasked again and an interrupt was latched earlier, the + device shall notify the driver again. + +\item The driver on receiving the notification from the device, processes the + interrupt. The interrupt is masked at the device until the buffers are + queued again by the driver. + +\item In a typical guest operating system kernel, the virtio-gpio driver + notifies the client driver, that is associated with this GPIO line, to + process the event. In the case of a level triggered interrupt, the client + driver shall fully process and acknowledge the event at its source to return + the line to its inactive state before the interrupt is unmasked again to + avoid a spurious interrupt. + +\item Once the interrupt is handled, the driver may queue a pair of buffers for + the GPIO line to unmask the interrupt again. + +\item The driver can also disable the interrupt by sending the + \field{VIRTIO_GPIO_MSG_SET_IRQ_TYPE} message, with + \field{VIRTIO_GPIO_IRQ_TYPE_NONE} trigger type. In that case, the device + shall return the unused pair of buffers for the GPIO line after setting the + \field{status} field with \field{VIRTIO_GPIO_IRQ_STATUS_INVALID}. +\end{itemize} + +\drivernormative{\subsubsection}{eventq Operation}{Device Types / GPIO Device / eventq Operation} + +\begin{itemize} +\item The driver MUST both enable and unmask the interrupt in order to get + notified for the same. + +\item To unmask the interrupt, the driver MUST queue a separate pair of buffers + to the \field{eventq} virtqueue for each GPIO line. + +\item The driver MUST NOT add multiple pairs of buffers for the same GPIO line + on the \field{eventq} virtqueue. +\end{itemize} + +\devicenormative{\subsubsection}{eventq Operation}{Device Types / GPIO Device / eventq Operation} + +\begin{itemize} +\item The device CAN ONLY send an interrupt event to the driver for a GPIO line, + if the interrupt is both unmasked and enabled by the driver. + +\item On receiving \field{VIRTIO_GPIO_MSG_SET_IRQ_TYPE} message, with + \field{VIRTIO_GPIO_IRQ_TYPE_NONE} trigger type, the device MUST return the + buffers, if they were received earlier, after setting the \field{status} + field to \field{VIRTIO_GPIO_IRQ_STATUS_INVALID}. \end{itemize}