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diff --git a/Documentation/scsi/53c700.rst b/Documentation/scsi/53c700.rst new file mode 100644 index 000000000..53a0e9f9c --- /dev/null +++ b/Documentation/scsi/53c700.rst @@ -0,0 +1,134 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================= +The 53c700 Driver Notes +======================= + +General Description +=================== + +This driver supports the 53c700 and 53c700-66 chips. It also supports +the 53c710 but only in 53c700 emulation mode. It is full featured and +does sync (-66 and 710 only), disconnects and tag command queueing. + +Since the 53c700 must be interfaced to a bus, you need to wrapper the +card detector around this driver. For an example, see the +NCR_D700.[ch] or lasi700.[ch] files. + +The comments in the 53c700.[ch] files tell you which parts you need to +fill in to get the driver working. + + +Compile Time Flags +================== + +A compile time flag is:: + + CONFIG_53C700_LE_ON_BE + +define if the chipset must be supported in little endian mode on a big +endian architecture (used for the 700 on parisc). + + +Using the Chip Core Driver +========================== + +In order to plumb the 53c700 chip core driver into a working SCSI +driver, you need to know three things about the way the chip is wired +into your system (or expansion card). + +1. The clock speed of the SCSI core +2. The interrupt line used +3. The memory (or io space) location of the 53c700 registers. + +Optionally, you may also need to know other things, like how to read +the SCSI Id from the card bios or whether the chip is wired for +differential operation. + +Usually you can find items 2. and 3. from general spec. documents or +even by examining the configuration of a working driver under another +operating system. + +The clock speed is usually buried deep in the technical literature. +It is required because it is used to set up both the synchronous and +asynchronous dividers for the chip. As a general rule of thumb, +manufacturers set the clock speed at the lowest possible setting +consistent with the best operation of the chip (although some choose +to drive it off the CPU or bus clock rather than going to the expense +of an extra clock chip). The best operation clock speeds are: + +========= ===== +53c700 25MHz +53c700-66 50MHz +53c710 40Mhz +========= ===== + +Writing Your Glue Driver +======================== + +This will be a standard SCSI driver (I don't know of a good document +describing this, just copy from some other driver) with at least a +detect and release entry. + +In the detect routine, you need to allocate a struct +NCR_700_Host_Parameters sized memory area and clear it (so that the +default values for everything are 0). Then you must fill in the +parameters that matter to you (see below), plumb the NCR_700_intr +routine into the interrupt line and call NCR_700_detect with the host +template and the new parameters as arguments. You should also call +the relevant request_*_region function and place the register base +address into the 'base' pointer of the host parameters. + +In the release routine, you must free the NCR_700_Host_Parameters that +you allocated, call the corresponding release_*_region and free the +interrupt. + +Handling Interrupts +------------------- + +In general, you should just plumb the card's interrupt line in with + +request_irq(irq, NCR_700_intr, <irq flags>, <driver name>, host); + +where host is the return from the relevant NCR_700_detect() routine. + +You may also write your own interrupt handling routine which calls +NCR_700_intr() directly. However, you should only really do this if +you have a card with more than one chip on it and you can read a +register to tell which set of chips wants the interrupt. + +Settable NCR_700_Host_Parameters +-------------------------------- + +The following are a list of the user settable parameters: + +clock: (MANDATORY) + Set to the clock speed of the chip in MHz. + +base: (MANDATORY) + Set to the base of the io or mem region for the register set. On 64 + bit architectures this is only 32 bits wide, so the registers must be + mapped into the low 32 bits of memory. + +pci_dev: (OPTIONAL) + Set to the PCI board device. Leave NULL for a non-pci board. This is + used for the pci_alloc_consistent() and pci_map_*() functions. + +dmode_extra: (OPTIONAL, 53c710 only) + Extra flags for the DMODE register. These are used to control bus + output pins on the 710. The settings should be a combination of + DMODE_FC1 and DMODE_FC2. What these pins actually do is entirely up + to the board designer. Usually it is safe to ignore this setting. + +differential: (OPTIONAL) + Set to 1 if the chip drives a differential bus. + +force_le_on_be: (OPTIONAL, only if CONFIG_53C700_LE_ON_BE is set) + Set to 1 if the chip is operating in little endian mode on a big + endian architecture. + +chip710: (OPTIONAL) + Set to 1 if the chip is a 53c710. + +burst_disable: (OPTIONAL, 53c710 only) + Disable 8 byte bursting for DMA transfers. |