[U-Boot] [PATCH 11/14] dm: add PCI design document

Marek Vasut
2012-08-08T11:42:27Z

From: Pavel Herrmann <morpheus.ibis@gmail.com>

Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
---
doc/driver-model/UDM-pci.txt | 265 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 265 insertions(+)
create mode 100644 doc/driver-model/UDM-pci.txt

diff --git a/doc/driver-model/UDM-pci.txt b/doc/driver-model/UDM-pci.txt
new file mode 100644
index 0000000..b65e9ea
--- /dev/null
+++ b/doc/driver-model/UDM-pci.txt
@@ -0,0 +1,265 @@
+The U-Boot Driver Model Project
+===============================
+PCI subsystem analysis
+======================
+
+Pavel Herrmann <morpheus.ibis@gmail.com>
+2012-03-17
+
+I) Overview
+-----------
+
+ U-Boot already supports multiple PCI busses, stored in a linked-list of
+ pci_controller structures. This structure contains generic driver data, bus
+ interface operations and private data for the driver.
+
+ Bus interface operations for PCI are (names are self-explanatory):
+
+ read_byte()
+ read_word()
+ read_dword()
+ write_byte()
+ write_word()
+ write_dword()
+
+ Each driver has to implement dword operations, and either implement word and
+ byte operations, or use shared $operation_config_$type_via_dword (eg.
+ read_config_byte_via_dword and similar) function. These functions are used
+ for config space I/O (read_config_dword and similar functions of the PCI
+ subsystem), which is used to configure the connected devices for standard MMIO
+ operations. All data transfers by respective device drivers are then done by
+ MMIO
+
+ Each driver also defines a separate init function, which has unique symbol
+ name, and thus more drivers can be compiled in without colliding. This init
+ function is typically called from pci_init_board(), different for each
+ particular board.
+
+ Some boards also define a function called fixup_irq, which gets called after
+ scanning the PCI bus for devices, and should dismiss any interrupts.
+
+ Several drivers are also located in arch/ and should be moved to drivers/pci.
+
+II) Approach
+------------
+
+ The pci_controller structure needs to be broken down to fit the new driver
+ model. Due to a large number of members, this will be done through three
+ distinct accessors, one for memory regions, one for config table and one for
+ everything else. That will make the pci_ops structure look like this:
+
+ struct pci_ops {
+ int (*read_byte)(struct instance *bus, pci_dev_t *dev, int addr,
+ u8 *buf);
+ int (*read_word)(struct instance *bus, pci_dev_t *dev, int addr,
+ u16 *buf);
+ int (*read_dword)(struct instance *bus, pci_dev_t *dev, int addr,
+ u32 *buf);
+ int (*write_byte)(struct instance *bus, pci_dev_t *dev, int addr,
+ u8 val);
+ int (*write_byte)(struct instance *bus, pci_dev_t *dev, int addr,
+ u8 val);
+ int (*write_dword)(struct instance *bus, pci_dev_t *dev, int addr,
+ u32 val);
+ void (*fixup_irq)(struct instance *bus, pci_dev_t *dev);
+ struct pci_region* (*get_region)(struct instance *, uint num);
+ struct pci_config_table* (*get_cfg_table)(struct instance *bus);
+ uint (*get_option)(struct instance * bus, enum pci_option_code op);
+ }
+
+ enum pci_option_code {
+ PCI_OPT_BUS_NUMBER=0,
+ PCI_OPT_REGION_COUNT,
+ PCI_OPT_INDIRECT_TYPE,
+ PCI_OPT_AUTO_MEM,
+ PCI_OPT_AUTO_IO,
+ PCI_OPT_AUTO_PREFETCH,
+ PCI_OPT_AUTO_FB,
+ PCI_OPT_CURRENT_BUS,
+ PCI_OPT_CFG_ADDR,
+ }
+
+ The return value for get_option will be an unsigned integer value for any
+ option code. If the option currently is a pointer to pci_region, it will
+ return an index for get_region function. Special case has to be made for
+ PCI_OPT_CFG_ADDR, which should be interpreted as a pointer, but it is only
+ used for equality in find_hose_by_cfg_addr, and thus can be returned as an
+ uint. Other function using cfg_addr value are read/write functions for
+ specific drivers (especially ops for indirect bridges), and thus have access
+ to private_data of the driver instance.
+
+ The config table accessor will return a pointer to a NULL-terminated array of
+ pci_config_table, which is supplied by the board in platform_data, or NULL if
+ the board didn't specify one. This table is used to override PnP
+ auto-initialization, or to specific initialization functions for non-PNP
+ devices.
+
+ Transparent PCI-PCI bridges will get their own driver, and will forward all
+ operations to operations of their parent bus. This however makes it
+ impossible to use instances to identify devices, as not all devices will be
+ directly visible to the respective bus driver.
+
+ Init functions of controller drivers will be moved to their respective
+ probe() functions, in accordance to the driver model.
+
+ The PCI core will handle all mapping functions currently found in pci.c, as
+ well as proxy functions for read/write operations of the drivers. The PCI
+ core will also handle bus scanning and device configuration.
+
+ The PnP helper functions currently in pci_auto.c will also be a part of PCI
+ core, but they will be exposed only to PCI controller drivers, not to other
+ device drivers.
+
+ The PCI API for device drivers will remain largely unchanged, most drivers
+ will require no changes at all, and all modifications will be limited to
+ changing the pci_controlle into instance*.
+
+III) Analysis of in-tree drivers
+--------------------------------
+
+ A) drivers in drivers/pci/
+ --------------------------
+
+ 1) pci_indirect.c
+ -----------------
+ Shared driver for indirect PCI bridges, several CONFIG macros - will
+ require significant cleanup.
+
+ 2) pci_ixp.c
+ ------------
+ Standard driver, specifies all read/write functions separately.
+
+ 3) pci_sh4.c
+ ------------
+ Shared init function for SH4 drivers, uses dword for read/write ops.
+
+ 4) pci_sh7751.c
+ ---------------
+ Standard driver, uses SH4 shared init.
+
+ 5) pci_sh7780.c
+ ---------------
+ Standard driver, uses SH4 shared init.
+
+ 6) tsi108_pci.c
+ ---------------
+ Standard driver, uses dword for read/write ops.
+
+ 7) fsl_pci_init.c
+ -----------------
+ Driver for PCI and PCI-e, uses indirect functions.
+
+ 8) pci_ftpci100.c
+ -----------------
+ Standard driver, uses indirect functions, has separate scan/setup
+ functions.
+
+ B) driver in arch/
+ ------------------
+
+ 1) x86/lib/pci_type1.c
+ ----------------------
+ Standard driver, specifies all read/write functions separately.
+
+ 2) m68k/cpu/mcf5445x/pci.c
+ --------------------------
+ Standard driver, specifies all read/write functions separately.
+
+ 3) m68k/cpu/mcf547x_8x/pci.c
+ ----------------------------
+ Standard driver, specifies all read/write functions separately.
+
+ 4) powerpc/cpu/mpc824x/pci.c
+ ----------------------------
+ Standard driver, uses indirect functions, does not setup HW.
+
+ 5) powerpc/cpu/mpc8260/pci.c
+ ----------------------------
+ Standard driver, uses indirect functions.
+
+ 6) powerpc/cpu/ppc4xx/4xx_pci.c
+ -------------------------------
+ Standard driver, uses indirect functions.
+
+ 7) powerpc/cpu/ppc4xx/4xx_pcie.c
+ --------------------------------
+ PCI-e driver, specifies all read/write functions separately.
+
+ 8) powerpc/cpu/mpc83xx/pci.c
+ ----------------------------
+ Standard driver, uses indirect functions.
+
+ 9) powerpc/cpu/mpc83xx/pcie.c
+ -----------------------------
+ PCI-e driver, specifies all read/write functions separately.
+
+ 10) powerpc/cpu/mpc5xxx/pci_mpc5200.c
+ -------------------------------------
+ Standard driver, uses dword for read/write ops.
+
+ 11) powerpc/cpu/mpc512x/pci.c
+ -----------------------------
+ Standard driver, uses indirect functions.
+
+ 12) powerpc/cpu/mpc8220/pci.c
+ -----------------------------
+ Standard driver, specifies all read/write functions separately.
+
+ 13) powerpc/cpu/mpc85xx/pci.c
+ -----------------------------
+ Standard driver, uses indirect functions, has two busses.
+
+ C) drivers in board/
+ --------------------
+
+ 1) eltec/elppc/pci.c
+ --------------------
+ Standard driver, uses indirect functions.
+
+ 2) amirix/ap1000/pci.c
+ ----------------------
+ Standard driver, specifies all read/write functions separately.
+
+ 3) prodrive/p3mx/pci.c
+ ----------------------
+ Standard driver, uses dword for read/write ops, has two busses.
+
+ 4) esd/cpci750/pci.c
+ --------------------
+ Standard driver, uses dword for read/write ops, has two busses.
+
+ 5) esd/common/pci.c
+ -------------------
+ Standard driver, uses dword for read/write ops.
+
+ 6) dave/common/pci.c
+ --------------------
+ Standard driver, uses dword for read/write ops.
+
+ 7) ppmc7xx/pci.c
+ ----------------
+ Standard driver, uses indirect functions.
+
+ 8) pcippc2/cpc710_pci.c
+ -----------------------
+ Standard driver, uses indirect functions, has two busses.
+
+ 9) Marvell/db64360/pci.c
+ ------------------------
+ Standard driver, uses dword for read/write ops, has two busses.
+
+ 10) Marvell/db64460/pci.c
+ -------------------------
+ Standard driver, uses dword for read/write ops, has two busses.
+
+ 11) evb64260/pci.c
+ ------------------
+ Standard driver, uses dword for read/write ops, has two busses.
+
+ 12) armltd/integrator/pci.c
+ ---------------------------
+ Standard driver, specifies all read/write functions separately.
+
+ All drivers will be moved to drivers/pci. Several drivers seem
+ similar/identical, especially those located under board, and may be merged
+ into one.
--
1.7.10.4