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dm: add PCI design document
Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
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Pavel Herrmann
Wolfgang Denk
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doc/driver-model/UDM-pci.txt
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doc/driver-model/UDM-pci.txt
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The U-Boot Driver Model Project
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===============================
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PCI subsystem analysis
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======================
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Pavel Herrmann <morpheus.ibis@gmail.com>
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2012-03-17
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I) Overview
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-----------
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U-Boot already supports multiple PCI busses, stored in a linked-list of
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pci_controller structures. This structure contains generic driver data, bus
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interface operations and private data for the driver.
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Bus interface operations for PCI are (names are self-explanatory):
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read_byte()
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read_word()
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read_dword()
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write_byte()
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write_word()
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write_dword()
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Each driver has to implement dword operations, and either implement word and
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byte operations, or use shared $operation_config_$type_via_dword (eg.
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read_config_byte_via_dword and similar) function. These functions are used
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for config space I/O (read_config_dword and similar functions of the PCI
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subsystem), which is used to configure the connected devices for standard MMIO
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operations. All data transfers by respective device drivers are then done by
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MMIO
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Each driver also defines a separate init function, which has unique symbol
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name, and thus more drivers can be compiled in without colliding. This init
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function is typically called from pci_init_board(), different for each
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particular board.
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Some boards also define a function called fixup_irq, which gets called after
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scanning the PCI bus for devices, and should dismiss any interrupts.
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Several drivers are also located in arch/ and should be moved to drivers/pci.
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II) Approach
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------------
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The pci_controller structure needs to be broken down to fit the new driver
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model. Due to a large number of members, this will be done through three
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distinct accessors, one for memory regions, one for config table and one for
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everything else. That will make the pci_ops structure look like this:
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struct pci_ops {
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int (*read_byte)(struct instance *bus, pci_dev_t *dev, int addr,
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u8 *buf);
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int (*read_word)(struct instance *bus, pci_dev_t *dev, int addr,
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u16 *buf);
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int (*read_dword)(struct instance *bus, pci_dev_t *dev, int addr,
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u32 *buf);
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int (*write_byte)(struct instance *bus, pci_dev_t *dev, int addr,
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u8 val);
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int (*write_byte)(struct instance *bus, pci_dev_t *dev, int addr,
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u8 val);
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int (*write_dword)(struct instance *bus, pci_dev_t *dev, int addr,
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u32 val);
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void (*fixup_irq)(struct instance *bus, pci_dev_t *dev);
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struct pci_region* (*get_region)(struct instance *, uint num);
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struct pci_config_table* (*get_cfg_table)(struct instance *bus);
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uint (*get_option)(struct instance * bus, enum pci_option_code op);
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}
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enum pci_option_code {
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PCI_OPT_BUS_NUMBER=0,
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PCI_OPT_REGION_COUNT,
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PCI_OPT_INDIRECT_TYPE,
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PCI_OPT_AUTO_MEM,
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PCI_OPT_AUTO_IO,
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PCI_OPT_AUTO_PREFETCH,
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PCI_OPT_AUTO_FB,
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PCI_OPT_CURRENT_BUS,
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PCI_OPT_CFG_ADDR,
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}
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The return value for get_option will be an unsigned integer value for any
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option code. If the option currently is a pointer to pci_region, it will
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return an index for get_region function. Special case has to be made for
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PCI_OPT_CFG_ADDR, which should be interpreted as a pointer, but it is only
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used for equality in find_hose_by_cfg_addr, and thus can be returned as an
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uint. Other function using cfg_addr value are read/write functions for
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specific drivers (especially ops for indirect bridges), and thus have access
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to private_data of the driver instance.
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The config table accessor will return a pointer to a NULL-terminated array of
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pci_config_table, which is supplied by the board in platform_data, or NULL if
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the board didn't specify one. This table is used to override PnP
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auto-initialization, or to specific initialization functions for non-PNP
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devices.
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Transparent PCI-PCI bridges will get their own driver, and will forward all
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operations to operations of their parent bus. This however makes it
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impossible to use instances to identify devices, as not all devices will be
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directly visible to the respective bus driver.
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Init functions of controller drivers will be moved to their respective
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probe() functions, in accordance to the driver model.
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The PCI core will handle all mapping functions currently found in pci.c, as
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well as proxy functions for read/write operations of the drivers. The PCI
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core will also handle bus scanning and device configuration.
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The PnP helper functions currently in pci_auto.c will also be a part of PCI
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core, but they will be exposed only to PCI controller drivers, not to other
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device drivers.
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The PCI API for device drivers will remain largely unchanged, most drivers
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will require no changes at all, and all modifications will be limited to
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changing the pci_controlle into instance*.
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III) Analysis of in-tree drivers
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--------------------------------
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A) drivers in drivers/pci/
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--------------------------
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1) pci_indirect.c
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-----------------
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Shared driver for indirect PCI bridges, several CONFIG macros - will
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require significant cleanup.
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2) pci_ixp.c
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------------
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Standard driver, specifies all read/write functions separately.
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3) pci_sh4.c
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------------
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Shared init function for SH4 drivers, uses dword for read/write ops.
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4) pci_sh7751.c
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---------------
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Standard driver, uses SH4 shared init.
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5) pci_sh7780.c
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---------------
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Standard driver, uses SH4 shared init.
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6) tsi108_pci.c
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---------------
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Standard driver, uses dword for read/write ops.
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7) fsl_pci_init.c
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-----------------
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Driver for PCI and PCI-e, uses indirect functions.
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8) pci_ftpci100.c
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-----------------
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Standard driver, uses indirect functions, has separate scan/setup
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functions.
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B) driver in arch/
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------------------
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1) x86/lib/pci_type1.c
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----------------------
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Standard driver, specifies all read/write functions separately.
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2) m68k/cpu/mcf5445x/pci.c
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--------------------------
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Standard driver, specifies all read/write functions separately.
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3) m68k/cpu/mcf547x_8x/pci.c
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----------------------------
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Standard driver, specifies all read/write functions separately.
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4) powerpc/cpu/mpc824x/pci.c
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----------------------------
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Standard driver, uses indirect functions, does not setup HW.
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5) powerpc/cpu/mpc8260/pci.c
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----------------------------
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Standard driver, uses indirect functions.
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6) powerpc/cpu/ppc4xx/4xx_pci.c
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-------------------------------
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Standard driver, uses indirect functions.
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7) powerpc/cpu/ppc4xx/4xx_pcie.c
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--------------------------------
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PCI-e driver, specifies all read/write functions separately.
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8) powerpc/cpu/mpc83xx/pci.c
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----------------------------
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Standard driver, uses indirect functions.
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9) powerpc/cpu/mpc83xx/pcie.c
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-----------------------------
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PCI-e driver, specifies all read/write functions separately.
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10) powerpc/cpu/mpc5xxx/pci_mpc5200.c
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-------------------------------------
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Standard driver, uses dword for read/write ops.
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11) powerpc/cpu/mpc512x/pci.c
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-----------------------------
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Standard driver, uses indirect functions.
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12) powerpc/cpu/mpc8220/pci.c
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-----------------------------
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Standard driver, specifies all read/write functions separately.
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13) powerpc/cpu/mpc85xx/pci.c
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-----------------------------
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Standard driver, uses indirect functions, has two busses.
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C) drivers in board/
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--------------------
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1) eltec/elppc/pci.c
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--------------------
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Standard driver, uses indirect functions.
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2) amirix/ap1000/pci.c
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----------------------
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Standard driver, specifies all read/write functions separately.
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3) prodrive/p3mx/pci.c
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----------------------
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Standard driver, uses dword for read/write ops, has two busses.
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4) esd/cpci750/pci.c
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--------------------
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Standard driver, uses dword for read/write ops, has two busses.
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5) esd/common/pci.c
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-------------------
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Standard driver, uses dword for read/write ops.
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6) dave/common/pci.c
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--------------------
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Standard driver, uses dword for read/write ops.
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7) ppmc7xx/pci.c
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----------------
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Standard driver, uses indirect functions.
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8) pcippc2/cpc710_pci.c
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-----------------------
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Standard driver, uses indirect functions, has two busses.
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9) Marvell/db64360/pci.c
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------------------------
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Standard driver, uses dword for read/write ops, has two busses.
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10) Marvell/db64460/pci.c
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-------------------------
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Standard driver, uses dword for read/write ops, has two busses.
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11) evb64260/pci.c
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------------------
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Standard driver, uses dword for read/write ops, has two busses.
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12) armltd/integrator/pci.c
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---------------------------
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Standard driver, specifies all read/write functions separately.
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All drivers will be moved to drivers/pci. Several drivers seem
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similar/identical, especially those located under board, and may be merged
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into one.
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