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FreeBSD busdma and SMPng driver conversion project

Contents

Project Goal

busdma

The busdma interfaces permit hardware device drivers to operate on a variety of platforms avoiding the encoding of platform-specific access methods into drivers. This lowers the maintenance costs for drivers across platforms, and improves the chances that a driver will "just work" on a new platform. Modifying a driver to make use of busdma is relatively straight forward, but does require familiarity with both the device driver and busdma primitives. For busdma to be used in FreeBSD, two sets of changes are generally required: adaptation of the busdma implementation to run on all platforms, and adaptation of drivers to use the framework. As such, status information on this project is broken down into platform support, and driver support (sorted by category). Completing this work requires a thorough audit of the system device drivers, then prioritized conversion of drivers. Drivers are also expected to use bus_space functions, and this column is sometimes used to denote a driver in need of conversion to bus_space as well.

INTR_MPSAFE

Hardware drivers register their interrupt handler with the bus_setup_intr() function. Setting the flag INTR_MPSAFE tells the system interrupt code to call the interrupt routine without holding the Giant mutex. This can give a significant performance gain on SMP systems.

Drivers can set this flag even if they are not fully locked down as long as their interrupt routine is careful about not touching other data structures in the driver. An easy way to do this is to check and clear the hardware interrupt status registers and then schedule the interrupt processing for a taskqueue or kernel thread.

SMPng locked

Drivers should employ mutexes and sx locks to protect their data structures and hardware registers from competing threads. Mutex operations are somewhat expensive, so a good strategy is combine as many atomic operations into a single mutex acquisition as possible.

p!=a safety

Intel PAE support requires that pointers and physical address representations be of differing sizes. This means that drivers must be written to use vm_paddr_t or bus_addr_t rather than assuming that physical addresses can be represented using a void *. In addition, format strings and casts must be carefully handled.

The task list below is not intended to be complete, but does represent a set of relevant and/or important components of the overall work. The "Responsible" field identifies a developer who has expressed willingness to be responsible for completing the identified task; this doesn't preclude others working on it, but suggests that coordination with the responsible party might be appropriate so as to avoid unnecessary duplication of work, and to maximize forward progress. If beginning work on a new area of substantial size, or one that appears unclaimed, it may be worth dropping an e-mail to Maxime Henrion to see if any progress has been made.

The definition of the date field varies depending on the status of a task. For completed tasks, it refers to the date completed or reported completed. For in-progress tasks, it refers to the date of the last update of the entry. For stalled tasks, it refers to the date that the task was declared stalled. For new tasks, it refers to the date the task was added to the list.

Tasks are sorted first by status, then by date.

Resources and Links

A series of manual pages related to this project can be found here:

  • Physical Address Extensions - pae(4)
  • Bus and Machine-independent DMA Mapping Interface - bus_dma(9)
  • Machine-dependent part of the Virtual Memory (VM) system - pmap(9)
  • Resource Management Functions - rman(9)

Platform Support Status

Task Responsible Last updated Status Details
alpha Bernd Walter November 14, 2005 Done There are problems for systems with large amounts of memory.
amd64 Peter Wemm July 1, 2003 Done Fully supported.
arm Olivier Houchard December 23, 2005 Done Fully supported.
ia64 Marcel Moolenaar December 10, 2002 Done There may be problems for systems with large amounts of memory.
i386 Sam Leffler December 9, 2002 Done Fully supported.
powerpc Peter Grehan January 15, 2003 Done Fully supported.
sparc64 Thomas Moestl January 6, 2003 Done Fully supported.

Network Interface Driver Status

Driver Responsible Last updated busdma INTR_MPSAFE SMPng locked a!=p Notes
if_an   December 23, 2005 Unknown Unknown Unknown Unknown  
if_ar     Not done Not done Not done Not done kvtop()
if_bge Bill Paul April 13, 2004 Done Done Done Done  
if_cp Roman Kurakin October 31, 2005 Done Done Done Not done  
if_cs Warner Losh December 23, 2005 Not done Not done Not done Unknown Needs bus_space conversion
if_ct Roman Kurakin October 31, 2005 Done Done Done Not done  
if_cx Roman Kurakin June 24, 2004 Done In progress In progress Not done  
if_dc Maxime Henrion August 19, 2005 Done Done Done Done  
if_de Maxime Henrion August 17, 2005 Done Done Done Not done  
if_ed Warner Losh December 23, 2005 Done Done Done Done  
if_em Prafulla Deuskar April 13, 2004 Done Done Done Done  
if_en Harti Brandt November 2, 2005 Done Not done Not done Done Locking present; not yet marked INTR_MPSAFE?
if_ep Matthew Dodd,Warner Losh April 13, 2004 Done Done Done Done  
if_ex Warner Losh Dcember 23, 2005 Done Not done Not done Done  
if_fatm Harti Brandt November 2, 2005 Done Done Done Done  
if_fwe     Not done Not done Not done Not done  
if_fxp Maxime Henrion April 13, 2004 Done Done Done Done  
if_gem Thomas Moestl July 31, 2005 Done Done Done Not done  
if_hatm Harti Brandt November 2, 2005 Done Done Done Done  
if_hme Thomas Moestl January 30, 2005 Done Done Done Done  
if_idt     Not done Not done Not done Not done vtophys()
if_lge   November 23, 2005 Not done Done Done Not done vtophys()
if_lmc   February 11, 2006 Done Done Done Unknown Untested on PAE
if_lnc David O'Brien   Not done Not done Not done Not done vtophys(). Please contact Poul-Henning Kamp for info/hardware.
if_mn     Not done Not done Not done Not done vtophys(). Please contact Poul-Henning Kamp for info/hardware.
if_my   August 17, 2005 Not done Done Done Not done vtophys()
if_nge   August 17, 2005 Not done Done Done Not done vtophys()
if_nve   November 23, 2005 Not done Done Done Not done vtophys()
if_pcn David O'Brien August 19, 2005 Not done Done Done Not done vtophys()
if_pdq     Not done Not done Not done Not done Mostly busdma, except for vtophys().
if_re   May 30, 2005 Done Done Done Done  
if_rl Bill Paul April 13, 2004 Done Done Done Not done  
if_sf   August 19, 2005 Not done Done Done Not done vtophys()
if_sis Bill Paul April 13, 2004 Done Done Done Not done  
if_sk   April 27, 2006 Done Done Done Not done vtophys()
if_sn Warner Losh December 23, 2005 Done Done Done Done  
if_snc   December 23, 2005 Unknown Unknown Unknown Unknown pc98 only device (although it could work with many cardbus bridges)
if_sr     Not done Not done Not done Not done vtophys()
if_ste   August 31, 2005 Not done Done Done Not done vtophys()
if_ti   December 13, 2005 Done Done Done Done  
if_tl   September 15, 2005 Not done Done Done Not done  
if_tx Maxime Henrion April 19, 2003 Done Not done Not done Needs testing  
if_txp   September 22, 2005 In progress Done Done Not done  
if_vr   April 23, 2004 Not done Done Done Not done  
if_vx   September 22, 2005 N/A Done Done Not done Uses PIO to copy mbufs to and from hardware.
if_wb   September 22, 2005 Not done Done Done Not done  
if_wi Sam Leffler, Warner Losh November 4, 2003 Unknown Done Unknown Unknown This driver needs lots of help
if_xe Warner Losh December 23, 2005 Done Done Done Done  
if_xl Maxime Henrion April 13, 2004 Done Done Done Done  

Storage Device Driver Status

Driver Responsible Last updated busdma INTR_MPSAFE SMPng locked a!=p Notes
aac Scott Long January 31, 2005 Done Done Done Done Not endian clean.
adv   December 9, 2002 Done Not done Not done Not done  
aha   April 13, 2004 Done In progress In progress Not done Uses BUSDMA, but may pun bus address with host address.
ahb   December 9, 2002 Done Not done Not done Not done  
ahc Justin Gibbs January 31, 2005 Done Not done Not done Done  
ahd Justin Gibbs January 31, 2005 Done Not done Not done Done  
aic   December 23, 2005 Unknown Unknown Unknown Unknown Neeeds evaluation
amd   December 14, 2002 Done Not done Not done Not done  
amr Scott Long January 30, 2005 Done Done Done Done  
asr   January 4, 2003 Not done Not done Not done Not done vtophys(). Requires major work. A new I2O framework would be desirable.
ata Søren Schmidt December 9, 2002 Done Done Done Done  
buslogic     Not done Not done Not done Not done vtophys()
ciss   December 9, 2002 Done Not done Not done Not done  
ct     Not done Not done Not done Not done  
dpt     Not done Not done Not done Not done vtophys()
fdc   December 23, 2005 Unknown Unknown Unknown Unknown Needs evaluation
ida   December 9, 2002 Done Not done Not done Not done  
iir   March 1, 2006 Done Done Done Done 64-bit DMA without bouncing is possible, but needs work.
isp   February 8, 2003 Done Done Not done Not done  
ips Scott Long January 30, 2005 Done Done Done Done  
mlx Scott Long February 8, 2003 Done In progress In progress Not done  
mly Scott Long February 8, 2003 Done In progress In progress Not done  
mpt   December 9, 2002 Done Done Not done Not done  
ncr     Not done Not done Not done Not done vtophys(). Please contact Poul-Henning Kamp for a possible source of hardware.
ncv     Unknown Unknown Unknown Unknown Needs evaluation
nsp     Unknown Unknown Unknown Unknown Needs evaluation
pst   April 11, 2003 Not done Done Not done Not done vtophys()
stg   December 9, 2002 Done Not done Not done Not done At least, it looks like it may well be.
sym   December 19, 2002 Done Not done Not done Not done  
trm Olivier Houchard December 9, 2002 Done Not done Not done Not done  
twe   December 9, 2002 Done Not done Not done Not done  
wds   February 2, 2005 Done Not done Not done Not done  

Miscellaneous Device Driver Status

Driver Responsible Last updated busdma INTR_MPSAFE SMPng locked a!=p Notes
agp   October 31, 2005 Not done Not done Not done Not done vtophys()
bktr Olivier Houchard January 15, 2003 In progress Not done Not done Not done vtophys()
digi     Not done Not done Not done Not done vtophys()
drm Eric Anholt October 27, 2003 In progress Done Done In progress vtophys(). The locking could use some review.
fb     Not done Not done Not done Not done vtophys()
firewire Hidetoshi Shimokawa April 17, 2003 Done Not done Not done Done vtophys()
hfa     Not done Not done Not done Not done vtophys()
hifn Sam Leffler April 13, 2004 Done Done Done Not done  
musycc     Not done Not done Not done Not done vtophys(). Please contact Poul-Henning Kamp for info/hardware.
pcm Olivier Houchard February 20, 2003 Done Done Not done Not done  
ubsec Sam Leffler April 13, 2004 Done Done Done Not done vtophys() is used in debugging printf.
usb John-Mark Gurney July 24, 2003 Done Not done Not done Needs testing a!=p should be clean, but requires further testing.

Documentation Status

Task Responsible Last updated Status Notes
Manual pages for the busdma API Hiten Pandya January 15, 2003 Done