</authorgroup>
<copyright>
- <year>2003</year>
+ <year>2003-2005</year>
<holder>Jeff Garzik</holder>
</copyright>
</para>
</chapter>
- <chapter id="libataThanks">
- <title>Thanks</title>
- <para>
- The bulk of the ATA knowledge comes thanks to long conversations with
- Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
- and SCSI specifications.
- </para>
- <para>
- Thanks to Alan Cox for pointing out similarities
- between SATA and SCSI, and in general for motivation to hack on
- libata.
- </para>
- <para>
- libata's device detection
- method, ata_pio_devchk, and in general all the early probing was
- based on extensive study of Hale Landis's probe/reset code in his
- ATADRVR driver (www.ata-atapi.com).
- </para>
- </chapter>
-
<chapter id="libataDriverApi">
<title>libata Driver API</title>
+ <para>
+ struct ata_port_operations is defined for every low-level libata
+ hardware driver, and it controls how the low-level driver
+ interfaces with the ATA and SCSI layers.
+ </para>
+ <para>
+ FIS-based drivers will hook into the system with ->qc_prep() and
+ ->qc_issue() high-level hooks. Hardware which behaves in a manner
+ similar to PCI IDE hardware may utilize several generic helpers,
+ defining at a bare minimum the bus I/O addresses of the ATA shadow
+ register blocks.
+ </para>
<sect1>
<title>struct ata_port_operations</title>
+ <sect2><title>Disable ATA port</title>
<programlisting>
void (*port_disable) (struct ata_port *);
</programlisting>
Called from ata_bus_probe() and ata_bus_reset() error paths,
as well as when unregistering from the SCSI module (rmmod, hot
unplug).
+ This function should do whatever needs to be done to take the
+ port out of use. In most cases, ata_port_disable() can be used
+ as this hook.
+ </para>
+ <para>
+ Called from ata_bus_probe() on a failed probe.
+ Called from ata_bus_reset() on a failed bus reset.
+ Called from ata_scsi_release().
</para>
+ </sect2>
+
+ <sect2><title>Post-IDENTIFY device configuration</title>
<programlisting>
void (*dev_config) (struct ata_port *, struct ata_device *);
</programlisting>
found. Typically used to apply device-specific fixups prior to
issue of SET FEATURES - XFER MODE, and prior to operation.
</para>
+ <para>
+ Called by ata_device_add() after ata_dev_identify() determines
+ a device is present.
+ </para>
+ <para>
+ This entry may be specified as NULL in ata_port_operations.
+ </para>
+
+ </sect2>
+ <sect2><title>Set PIO/DMA mode</title>
<programlisting>
void (*set_piomode) (struct ata_port *, struct ata_device *);
void (*set_dmamode) (struct ata_port *, struct ata_device *);
->set_dma_mode() is only called if DMA is possible.
</para>
+ </sect2>
+
+ <sect2><title>Taskfile read/write</title>
<programlisting>
void (*tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
registers / DMA buffers. ->tf_read() is called to read the
hardware registers / DMA buffers, to obtain the current set of
taskfile register values.
+ Most drivers for taskfile-based hardware (PIO or MMIO) use
+ ata_tf_load() and ata_tf_read() for these hooks.
</para>
+ </sect2>
+
+ <sect2><title>ATA command execute</title>
<programlisting>
void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
</programlisting>
<para>
causes an ATA command, previously loaded with
->tf_load(), to be initiated in hardware.
+ Most drivers for taskfile-based hardware use ata_exec_command()
+ for this hook.
+ </para>
+
+ </sect2>
+
+ <sect2><title>Per-cmd ATAPI DMA capabilities filter</title>
+ <programlisting>
+int (*check_atapi_dma) (struct ata_queued_cmd *qc);
+ </programlisting>
+
+ <para>
+Allow low-level driver to filter ATA PACKET commands, returning a status
+indicating whether or not it is OK to use DMA for the supplied PACKET
+command.
</para>
+ <para>
+ This hook may be specified as NULL, in which case libata will
+ assume that atapi dma can be supported.
+ </para>
+
+ </sect2>
+ <sect2><title>Read specific ATA shadow registers</title>
<programlisting>
u8 (*check_status)(struct ata_port *ap);
-void (*dev_select)(struct ata_port *ap, unsigned int device);
+u8 (*check_altstatus)(struct ata_port *ap);
+u8 (*check_err)(struct ata_port *ap);
</programlisting>
<para>
- Reads the Status ATA shadow register from hardware. On some
- hardware, this has the side effect of clearing the interrupt
- condition.
+ Reads the Status/AltStatus/Error ATA shadow register from
+ hardware. On some hardware, reading the Status register has
+ the side effect of clearing the interrupt condition.
+ Most drivers for taskfile-based hardware use
+ ata_check_status() for this hook.
+ </para>
+ <para>
+ Note that because this is called from ata_device_add(), at
+ least a dummy function that clears device interrupts must be
+ provided for all drivers, even if the controller doesn't
+ actually have a taskfile status register.
</para>
+ </sect2>
+
+ <sect2><title>Select ATA device on bus</title>
<programlisting>
void (*dev_select)(struct ata_port *ap, unsigned int device);
</programlisting>
<para>
Issues the low-level hardware command(s) that causes one of N
hardware devices to be considered 'selected' (active and
- available for use) on the ATA bus.
+ available for use) on the ATA bus. This generally has no
+ meaning on FIS-based devices.
+ </para>
+ <para>
+ Most drivers for taskfile-based hardware use
+ ata_std_dev_select() for this hook. Controllers which do not
+ support second drives on a port (such as SATA contollers) will
+ use ata_noop_dev_select().
</para>
+ </sect2>
+
+ <sect2><title>Reset ATA bus</title>
<programlisting>
void (*phy_reset) (struct ata_port *ap);
</programlisting>
for device presence (PATA and SATA), typically a soft reset
(SRST) will be performed. Drivers typically use the helper
functions ata_bus_reset() or sata_phy_reset() for this hook.
+ Many SATA drivers use sata_phy_reset() or call it from within
+ their own phy_reset() functions.
</para>
+ </sect2>
+
+ <sect2><title>Control PCI IDE BMDMA engine</title>
<programlisting>
void (*bmdma_setup) (struct ata_queued_cmd *qc);
void (*bmdma_start) (struct ata_queued_cmd *qc);
+void (*bmdma_stop) (struct ata_port *ap);
+u8 (*bmdma_status) (struct ata_port *ap);
</programlisting>
<para>
- When setting up an IDE BMDMA transaction, these hooks arm
- (->bmdma_setup) and fire (->bmdma_start) the hardware's DMA
- engine.
+When setting up an IDE BMDMA transaction, these hooks arm
+(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
+the hardware's DMA engine. ->bmdma_status is used to read the standard
+PCI IDE DMA Status register.
</para>
+ <para>
+These hooks are typically either no-ops, or simply not implemented, in
+FIS-based drivers.
+ </para>
+ <para>
+Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup()
+hook. ata_bmdma_setup() will write the pointer to the PRD table to
+the IDE PRD Table Address register, enable DMA in the DMA Command
+register, and call exec_command() to begin the transfer.
+ </para>
+ <para>
+Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start()
+hook. ata_bmdma_start() will write the ATA_DMA_START flag to the DMA
+Command register.
+ </para>
+ <para>
+Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop()
+hook. ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA
+command register.
+ </para>
+ <para>
+Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.
+ </para>
+
+ </sect2>
+
+ <sect2><title>High-level taskfile hooks</title>
<programlisting>
void (*qc_prep) (struct ata_queued_cmd *qc);
int (*qc_issue) (struct ata_queued_cmd *qc);
->qc_issue is used to make a command active, once the hardware
and S/G tables have been prepared. IDE BMDMA drivers use the
helper function ata_qc_issue_prot() for taskfile protocol-based
- dispatch. More advanced drivers roll their own ->qc_issue
- implementation, using this as the "issue new ATA command to
- hardware" hook.
+ dispatch. More advanced drivers implement their own ->qc_issue.
+ </para>
+ <para>
+ ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
+ ->bmdma_start() as necessary to initiate a transfer.
</para>
+ </sect2>
+
+ <sect2><title>Timeout (error) handling</title>
<programlisting>
void (*eng_timeout) (struct ata_port *ap);
</programlisting>
<para>
- This is a high level error handling function, called from the
- error handling thread, when a command times out.
+This is a high level error handling function, called from the
+error handling thread, when a command times out. Most newer
+hardware will implement its own error handling code here. IDE BMDMA
+drivers may use the helper function ata_eng_timeout().
</para>
+ </sect2>
+
+ <sect2><title>Hardware interrupt handling</title>
<programlisting>
irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
void (*irq_clear) (struct ata_port *);
before the interrupt handler is registered, to be sure hardware
is quiet.
</para>
+ <para>
+ The second argument, dev_instance, should be cast to a pointer
+ to struct ata_host_set.
+ </para>
+ <para>
+ Most legacy IDE drivers use ata_interrupt() for the
+ irq_handler hook, which scans all ports in the host_set,
+ determines which queued command was active (if any), and calls
+ ata_host_intr(ap,qc).
+ </para>
+ <para>
+ Most legacy IDE drivers use ata_bmdma_irq_clear() for the
+ irq_clear() hook, which simply clears the interrupt and error
+ flags in the DMA status register.
+ </para>
+ </sect2>
+
+ <sect2><title>SATA phy read/write</title>
<programlisting>
u32 (*scr_read) (struct ata_port *ap, unsigned int sc_reg);
void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
<para>
Read and write standard SATA phy registers. Currently only used
if ->phy_reset hook called the sata_phy_reset() helper function.
+ sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
</para>
+ </sect2>
+
+ <sect2><title>Init and shutdown</title>
<programlisting>
int (*port_start) (struct ata_port *ap);
void (*port_stop) (struct ata_port *ap);
->port_start() is called just after the data structures for each
port are initialized. Typically this is used to alloc per-port
DMA buffers / tables / rings, enable DMA engines, and similar
- tasks.
+ tasks. Some drivers also use this entry point as a chance to
+ allocate driver-private memory for ap->private_data.
</para>
<para>
- ->host_stop() is called when the rmmod or hot unplug process
- begins. The hook must stop all hardware interrupts, DMA
- engines, etc.
+ Many drivers use ata_port_start() as this hook or call
+ it from their own port_start() hooks. ata_port_start()
+ allocates space for a legacy IDE PRD table and returns.
</para>
<para>
->port_stop() is called after ->host_stop(). It's sole function
is to release DMA/memory resources, now that they are no longer
- actively being used.
+ actively being used. Many drivers also free driver-private
+ data from port at this time.
+ </para>
+ <para>
+ Many drivers use ata_port_stop() as this hook, which frees the
+ PRD table.
+ </para>
+ <para>
+ ->host_stop() is called after all ->port_stop() calls
+have completed. The hook must finalize hardware shutdown, release DMA
+and other resources, etc.
+ This hook may be specified as NULL, in which case it is not called.
</para>
+ </sect2>
+
</sect1>
</chapter>
!Idrivers/scsi/sata_sil.c
</chapter>
+ <chapter id="libataThanks">
+ <title>Thanks</title>
+ <para>
+ The bulk of the ATA knowledge comes thanks to long conversations with
+ Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
+ and SCSI specifications.
+ </para>
+ <para>
+ Thanks to Alan Cox for pointing out similarities
+ between SATA and SCSI, and in general for motivation to hack on
+ libata.
+ </para>
+ <para>
+ libata's device detection
+ method, ata_pio_devchk, and in general all the early probing was
+ based on extensive study of Hale Landis's probe/reset code in his
+ ATADRVR driver (www.ata-atapi.com).
+ </para>
+ </chapter>
+
</book>