/*
* NCR 5380 generic driver routines. These should make it *trivial*
* to implement 5380 SCSI drivers under Linux with a non-trantor
* architecture.
*
* Note that these routines also work with NR53c400 family chips.
*
* Copyright 1993, Drew Eckhardt
* Visionary Computing
* (Unix and Linux consulting and custom programming)
* drew@colorado.edu
* +1 (303) 666-5836
*
* DISTRIBUTION RELEASE 6.
*
* For more information, please consult
*
* NCR 5380 Family
* SCSI Protocol Controller
* Databook
*
* NCR Microelectronics
* 1635 Aeroplaza Drive
* Colorado Springs, CO 80916
* 1+ (719) 578-3400
* 1+ (800) 334-5454
*/
/*
* ++roman: To port the 5380 driver to the Atari, I had to do some changes in
* this file, too:
*
* - Some of the debug statements were incorrect (undefined variables and the
* like). I fixed that.
*
* - In information_transfer(), I think a #ifdef was wrong. Looking at the
* possible DMA transfer size should also happen for REAL_DMA. I added this
* in the #if statement.
*
* - When using real DMA, information_transfer() should return in a DATAOUT
* phase after starting the DMA. It has nothing more to do.
*
* - The interrupt service routine should run main after end of DMA, too (not
* only after RESELECTION interrupts). Additionally, it should _not_ test
* for more interrupts after running main, since a DMA process may have
* been started and interrupts are turned on now. The new int could happen
* inside the execution of NCR5380_intr(), leading to recursive
* calls.
*
* - I've added a function merge_contiguous_buffers() that tries to
* merge scatter-gather buffers that are located at contiguous
* physical addresses and can be processed with the same DMA setup.
* Since most scatter-gather operations work on a page (4K) of
* 4 buffers (1K), in more than 90% of all cases three interrupts and
* DMA setup actions are saved.
*
* - I've deleted all the stuff for AUTOPROBE_IRQ, REAL_DMA_POLL, PSEUDO_DMA
* and USLEEP, because these were messing up readability and will never be
* needed for Atari SCSI.
*
* - I've revised the NCR5380_main() calling scheme (relax the 'main_running'
* stuff), and 'main' is executed in a bottom half if awoken by an
* interrupt.
*
* - The code was quite cluttered up by "#if (NDEBUG & NDEBUG_*) printk..."
* constructs. In my eyes, this made the source rather unreadable, so I
* finally replaced that by the *_PRINTK() macros.
*
*/
/*
* Further development / testing that should be done :
* 1. Test linked command handling code after Eric is ready with
* the high level code.
*/
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_transport_spi.h>
#if (NDEBUG & NDEBUG_LISTS)
#define LIST(x, y) \
do { \
printk("LINE:%d Adding %p to %p\n", \
__LINE__, (void*)(x), (void*)(y)); \
if ((x) == (y)) \
udelay(5); \
} while (0)
#define REMOVE(w, x, y, z) \
do { \
printk("LINE:%d Removing: %p->%p %p->%p \n", \
__LINE__, (void*)(w), (void*)(x), \
(void*)(y), (void*)(z)); \
if ((x) == (y)) \
udelay(5); \
} while (0)
#else
#define LIST(x,y)
#define REMOVE(w,x,y,z)
#endif
#ifndef notyet
#undef LINKED
#endif
/*
* Design
* Issues :
*
* The other Linux SCSI drivers were written when Linux was Intel PC-only,
* and specifically for each board rather than each chip. This makes their
* adaptation to platforms like the Mac (Some of which use NCR5380's)
* more difficult than it has to be.
*
* Also, many of the SCSI drivers were written before the command queuing
* routines were implemented, meaning their implementations of queued
* commands were hacked on rather than designed in from the start.
*
* When I designed the Linux SCSI drivers I figured that
* while having two different SCSI boards in a system might be useful
* for debugging things, two of the same type wouldn't be used.
* Well, I was wrong and a number of users have mailed me about running
* multiple high-performance SCSI boards in a server.
*
* Finally, when I get questions from users, I have no idea what
* revision of my driver they are running.
*
* This driver attempts to address these problems :
* This is a generic 5380 driver. To use it on a different platform,
* one simply writes appropriate system specific macros (ie, data
* transfer - some PC's will use the I/O bus, 68K's must use
* memory mapped) and drops this file in their 'C' wrapper.
*
* As far as command queueing, two queues are maintained for
* each 5380 in the system - commands that haven't been issued yet,
* and commands that are currently executing. This means that an
* unlimited number of commands may be queued, letting
* more commands propagate from the higher driver levels giving higher
* throughput. Note that both I_T_L and I_T_L_Q nexuses are supported,
* allowing multiple commands to propagate all the way to a SCSI-II device
* while a command is already executing.
*
* To solve the multiple-boards-in-the-same-system problem,
* there is a separate instance structure for each instance
* of a 5380 in the system. So, multiple NCR5380 drivers will
* be able to coexist with appropriate changes to the high level
* SCSI code.
*
* A NCR5380_PUBLIC_REVISION macro is provided, with the release
* number (updated for each public release) printed by the
* NCR5380_print_options command, which should be called from the
* wrapper detect function, so that I know what release of the driver
* users are using.
*
* Issues specific to the NCR5380 :
*
* When used in a PIO or pseudo-dma mode, the NCR5380 is a braindead
* piece of hardware that requires you to sit in a loop polling for
* the REQ signal as long as you are connected. Some devices are
* brain dead (ie, many TEXEL CD ROM drives) and won't disconnect
* while doing long seek operations.
*
* The workaround for this is to keep track of devices that have
* disconnected. If the device hasn't disconnected, for commands that
* should disconnect, we do something like
*
* while (!REQ is asserted) { sleep for N usecs; poll for M usecs }
*
* Some tweaking of N and M needs to be done. An algorithm based
* on "time to data" would give the best results as long as short time
* to datas (ie, on the same track) were considered, however these
* broken devices are the exception rather than the rule and I'd rather
* spend my time optimizing for the normal case.
*
* Architecture :
*
* At the heart of the design is a coroutine, NCR5380_main,
* which is started when not running by the interrupt handler,
* timer, and queue command function. It attempts to establish
* I_T_L or I_T_L_Q nexuses by removing the commands from the
* issue queue and calling NCR5380_select() if a nexus
* is not established.
*
* Once a nexus is established, the NCR5380_information_transfer()
* phase goes through the various phases as instructed by the target.
* if the target goes into MSG IN and sends a DISCONNECT message,
* the command structure is placed into the per instance disconnected
* queue, and NCR5380_main tries to find more work. If USLEEP
* was defined, and the target is idle for too long, the system
* will try to sleep.
*
* If a command has disconnected, eventually an interrupt will trigger,
* calling NCR5380_intr() which will in turn call NCR5380_reselect
* to reestablish a nexus. This will run main if necessary.
*
* On command termination, the done function will be called as
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