📄 periph_using_irqs.htm
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<title>SDIO Card IRQs</title>
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<font color="#FFFFFF" size="5" face="Arial, Helvetica, sans-serif"><strong>Embedded SDIO Driver Kit Help </strong></font></td>
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<p class="Topic"><!-- InstanceBeginEditable name="SubTemplate" --> SDIO Card
IRQs<!-- InstanceEndEditable --> </p>
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<p class="BODYTEXT">A function driver registers an interrupt request (IRQ) handler
with the following form:</p>
<p class="BODYTEXT"><font face="Courier New, Courier, mono">void IrqHandler(PVOID
pContext);</font></p>
<p class="BODYTEXT">The driver can register a handler that allows synchronous
I/O requests or a handler that requires the use of asynchronous I/O requests.
Only one handler of either type is allowed for each <font face="Courier New, Courier, mono">PSDDEVICE</font> instance.
In a multi-function card, the interrupt request signal is shared between all
I/O functions and one or more function drivers may each set a separate IRQ
handler for each <font face="Courier New, Courier, mono">PSDDEVICE</font>.
SDIO cards implement a card-wide IRQ pending register to relay to
the host which functions are interrupting. The function driver's interrupt
handler is called only if its interrupt
status bit is set in the IRQ pending
register.</p>
<p class="BODYTEXT"><strong>Synchronous IRQ processing:</strong></p>
<p class="BODYTEXT">Most drivers can use the synchronous mode of processing and
a handler can be set using the <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDDEVICE_SET_IRQ_HANDLER">SDDEVICE_SET_IRQ_HANDLER()</a></font> macro.
This mode allows
the
handler to make blocking (synchronous) I/O requests. This can greatly simplify
IRQ processing at the consequence of blocking all other interrupt handlers
on a multi-function card. The interrupt handler must issue a configuration
request to the SDIO core using the <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDCONFIG_FUNC_ACK_IRQ">SDCONFIG_FUNC_ACK_IRQ</a></font> to
acknowledge that it has completed its IRQ processing.</p>
<p class="BODYTEXT"><strong>Asynchronous IRQ processing:</strong></p>
<p class="BODYTEXT">Asynchronous IRQ handlers may be called in a non-premptible
context and called before all synchronous IRQ handlers. The handler typically
runs in a higher priority (relative to synchronous IRQ) execution
context and can process interrupts with lower latency. The consequence of
using this
mode
is that
only
asynchronous
(non-blocking) I/O
requests are
allowed
and can make the interrupt processing more complex. A
driver can use the <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDDEVICE_SET_ASYNC_IRQ_HANDLER">SDDEVICE_SET_ASYNC_IRQ_HANDLER()</a></font> macro
to set this type of handler. The interrupt handler must issue a configuration
request to the SDIO core using the <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDCONFIG_FUNC_ACK_IRQ">SDCONFIG_FUNC_ACK_IRQ</a></font> to
acknowledge that it has completed its IRQ processing.</p>
<p class="BODYTEXT"><strong><a name="EnableDisableIrq"></a>Enabling/Disabling IRQ:</strong></p>
<p class="BODYTEXT">The driver enables/unmasks and disables/masks its function
interrupt using the <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDCONFIG_FUNC_UNMASK_IRQ">SDCONFIG_FUNC_UNMASK_IRQ</a></font> and <font face="Courier New, Courier, mono"><a href="PD_Reference.htm#FUNC_SDCONFIG_FUNC_MASK_IRQ">SDCONFIG_FUNC_MASK_IRQ</a></font>configuration
requests. The driver must set up a handler prior to unmasking its IRQ. These
configuration requests may not occur immediately and may be deferred
depending on the state of the host controller driver.
A function driver should not assume that unmasking or masking it's IRQ
is immediate. Consequently, masking/unmasking configuration requests are inadequate
for synchronizing with a registered interrupt handler (async or sync). If synchronization
is required, the driver should use a synchronization primitive such as a semaphore
to guard
against a synchronous IRQ handler, or a critical section for asynchronous IRQ
handlers. If a critical section is used to block an asynchronous IRQ handler,
the driver should not hold the lock if a synchronous bus
request is submitted. This will result in a deadlock.</p>
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