diff options
Diffstat (limited to 'Documentation/arm')
| -rw-r--r-- | Documentation/arm/OMAP/omap_pm | 129 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/ADSBitsy | 2 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/Assabet | 2 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/Brutus | 2 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/GraphicsClient | 4 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/GraphicsMaster | 4 | ||||
| -rw-r--r-- | Documentation/arm/SA1100/Victor | 2 | ||||
| -rw-r--r-- | Documentation/arm/tcm.txt | 147 |
8 files changed, 284 insertions, 8 deletions
diff --git a/Documentation/arm/OMAP/omap_pm b/Documentation/arm/OMAP/omap_pm new file mode 100644 index 000000000000..5389440aade3 --- /dev/null +++ b/Documentation/arm/OMAP/omap_pm @@ -0,0 +1,129 @@ + +The OMAP PM interface +===================== + +This document describes the temporary OMAP PM interface. Driver +authors use these functions to communicate minimum latency or +throughput constraints to the kernel power management code. +Over time, the intention is to merge features from the OMAP PM +interface into the Linux PM QoS code. + +Drivers need to express PM parameters which: + +- support the range of power management parameters present in the TI SRF; + +- separate the drivers from the underlying PM parameter + implementation, whether it is the TI SRF or Linux PM QoS or Linux + latency framework or something else; + +- specify PM parameters in terms of fundamental units, such as + latency and throughput, rather than units which are specific to OMAP + or to particular OMAP variants; + +- allow drivers which are shared with other architectures (e.g., + DaVinci) to add these constraints in a way which won't affect non-OMAP + systems, + +- can be implemented immediately with minimal disruption of other + architectures. + + +This document proposes the OMAP PM interface, including the following +five power management functions for driver code: + +1. Set the maximum MPU wakeup latency: + (*pdata->set_max_mpu_wakeup_lat)(struct device *dev, unsigned long t) + +2. Set the maximum device wakeup latency: + (*pdata->set_max_dev_wakeup_lat)(struct device *dev, unsigned long t) + +3. Set the maximum system DMA transfer start latency (CORE pwrdm): + (*pdata->set_max_sdma_lat)(struct device *dev, long t) + +4. Set the minimum bus throughput needed by a device: + (*pdata->set_min_bus_tput)(struct device *dev, u8 agent_id, unsigned long r) + +5. Return the number of times the device has lost context + (*pdata->get_dev_context_loss_count)(struct device *dev) + + +Further documentation for all OMAP PM interface functions can be +found in arch/arm/plat-omap/include/mach/omap-pm.h. + + +The OMAP PM layer is intended to be temporary +--------------------------------------------- + +The intention is that eventually the Linux PM QoS layer should support +the range of power management features present in OMAP3. As this +happens, existing drivers using the OMAP PM interface can be modified +to use the Linux PM QoS code; and the OMAP PM interface can disappear. + + +Driver usage of the OMAP PM functions +------------------------------------- + +As the 'pdata' in the above examples indicates, these functions are +exposed to drivers through function pointers in driver .platform_data +structures. The function pointers are initialized by the board-*.c +files to point to the corresponding OMAP PM functions: +.set_max_dev_wakeup_lat will point to +omap_pm_set_max_dev_wakeup_lat(), etc. Other architectures which do +not support these functions should leave these function pointers set +to NULL. Drivers should use the following idiom: + + if (pdata->set_max_dev_wakeup_lat) + (*pdata->set_max_dev_wakeup_lat)(dev, t); + +The most common usage of these functions will probably be to specify +the maximum time from when an interrupt occurs, to when the device +becomes accessible. To accomplish this, driver writers should use the +set_max_mpu_wakeup_lat() function to to constrain the MPU wakeup +latency, and the set_max_dev_wakeup_lat() function to constrain the +device wakeup latency (from clk_enable() to accessibility). For +example, + + /* Limit MPU wakeup latency */ + if (pdata->set_max_mpu_wakeup_lat) + (*pdata->set_max_mpu_wakeup_lat)(dev, tc); + + /* Limit device powerdomain wakeup latency */ + if (pdata->set_max_dev_wakeup_lat) + (*pdata->set_max_dev_wakeup_lat)(dev, td); + + /* total wakeup latency in this example: (tc + td) */ + +The PM parameters can be overwritten by calling the function again +with the new value. The settings can be removed by calling the +function with a t argument of -1 (except in the case of +set_max_bus_tput(), which should be called with an r argument of 0). + +The fifth function above, omap_pm_get_dev_context_loss_count(), +is intended as an optimization to allow drivers to determine whether the +device has lost its internal context. If context has been lost, the +driver must restore its internal context before proceeding. + + +Other specialized interface functions +------------------------------------- + +The five functions listed above are intended to be usable by any +device driver. DSPBridge and CPUFreq have a few special requirements. +DSPBridge expresses target DSP performance levels in terms of OPP IDs. +CPUFreq expresses target MPU performance levels in terms of MPU +frequency. The OMAP PM interface contains functions for these +specialized cases to convert that input information (OPPs/MPU +frequency) into the form that the underlying power management +implementation needs: + +6. (*pdata->dsp_get_opp_table)(void) + +7. (*pdata->dsp_set_min_opp)(u8 opp_id) + +8. (*pdata->dsp_get_opp)(void) + +9. (*pdata->cpu_get_freq_table)(void) + +10. (*pdata->cpu_set_freq)(unsigned long f) + +11. (*pdata->cpu_get_freq)(void) diff --git a/Documentation/arm/SA1100/ADSBitsy b/Documentation/arm/SA1100/ADSBitsy index ab47c3833908..7197a9e958ee 100644 --- a/Documentation/arm/SA1100/ADSBitsy +++ b/Documentation/arm/SA1100/ADSBitsy @@ -40,4 +40,4 @@ Notes: mode, the timing is off so the image is corrupted. This will be fixed soon. -Any contribution can be sent to nico@cam.org and will be greatly welcome! +Any contribution can be sent to nico@fluxnic.net and will be greatly welcome! diff --git a/Documentation/arm/SA1100/Assabet b/Documentation/arm/SA1100/Assabet index 78bc1c1b04e5..91f7ce7ba426 100644 --- a/Documentation/arm/SA1100/Assabet +++ b/Documentation/arm/SA1100/Assabet @@ -240,7 +240,7 @@ Then, rebooting the Assabet is just a matter of waiting for the login prompt. Nicolas Pitre -nico@cam.org +nico@fluxnic.net June 12, 2001 diff --git a/Documentation/arm/SA1100/Brutus b/Documentation/arm/SA1100/Brutus index 2254c8f0b326..b1cfd405dccc 100644 --- a/Documentation/arm/SA1100/Brutus +++ b/Documentation/arm/SA1100/Brutus @@ -60,7 +60,7 @@ little modifications. Any contribution is welcome. -Please send patches to nico@cam.org +Please send patches to nico@fluxnic.net Have Fun ! diff --git a/Documentation/arm/SA1100/GraphicsClient b/Documentation/arm/SA1100/GraphicsClient index 8fa7e8027ff1..6c9c4f5a36e1 100644 --- a/Documentation/arm/SA1100/GraphicsClient +++ b/Documentation/arm/SA1100/GraphicsClient @@ -4,7 +4,7 @@ For more details, contact Applied Data Systems or see http://www.applieddata.net/products.html The original Linux support for this product has been provided by -Nicolas Pitre <nico@cam.org>. Continued development work by +Nicolas Pitre <nico@fluxnic.net>. Continued development work by Woojung Huh <whuh@applieddata.net> It's currently possible to mount a root filesystem via NFS providing a @@ -94,5 +94,5 @@ Notes: mode, the timing is off so the image is corrupted. This will be fixed soon. -Any contribution can be sent to nico@cam.org and will be greatly welcome! +Any contribution can be sent to nico@fluxnic.net and will be greatly welcome! diff --git a/Documentation/arm/SA1100/GraphicsMaster b/Documentation/arm/SA1100/GraphicsMaster index dd28745ac521..ee7c6595f23f 100644 --- a/Documentation/arm/SA1100/GraphicsMaster +++ b/Documentation/arm/SA1100/GraphicsMaster @@ -4,7 +4,7 @@ For more details, contact Applied Data Systems or see http://www.applieddata.net/products.html The original Linux support for this product has been provided by -Nicolas Pitre <nico@cam.org>. Continued development work by +Nicolas Pitre <nico@fluxnic.net>. Continued development work by Woojung Huh <whuh@applieddata.net> Use 'make graphicsmaster_config' before any 'make config'. @@ -50,4 +50,4 @@ Notes: mode, the timing is off so the image is corrupted. This will be fixed soon. -Any contribution can be sent to nico@cam.org and will be greatly welcome! +Any contribution can be sent to nico@fluxnic.net and will be greatly welcome! diff --git a/Documentation/arm/SA1100/Victor b/Documentation/arm/SA1100/Victor index 01e81fc49461..f938a29fdc20 100644 --- a/Documentation/arm/SA1100/Victor +++ b/Documentation/arm/SA1100/Victor @@ -9,7 +9,7 @@ Of course Victor is using Linux as its main operating system. The Victor implementation for Linux is maintained by Nicolas Pitre: nico@visuaide.com - nico@cam.org + nico@fluxnic.net For any comments, please feel free to contact me through the above addresses. diff --git a/Documentation/arm/tcm.txt b/Documentation/arm/tcm.txt new file mode 100644 index 000000000000..77fd9376e6d7 --- /dev/null +++ b/Documentation/arm/tcm.txt @@ -0,0 +1,147 @@ +ARM TCM (Tightly-Coupled Memory) handling in Linux +---- +Written by Linus Walleij <linus.walleij@stericsson.com> + +Some ARM SoC:s have a so-called TCM (Tightly-Coupled Memory). +This is usually just a few (4-64) KiB of RAM inside the ARM +processor. + +Due to being embedded inside the CPU The TCM has a +Harvard-architecture, so there is an ITCM (instruction TCM) +and a DTCM (data TCM). The DTCM can not contain any +instructions, but the ITCM can actually contain data. +The size of DTCM or ITCM is minimum 4KiB so the typical +minimum configuration is 4KiB ITCM and 4KiB DTCM. + +ARM CPU:s have special registers to read out status, physical +location and size of TCM memories. arch/arm/include/asm/cputype.h +defines a CPUID_TCM register that you can read out from the +system control coprocessor. Documentation from ARM can be found +at http://infocenter.arm.com, search for "TCM Status Register" +to see documents for all CPUs. Reading this register you can +determine if ITCM (bit 0) and/or DTCM (bit 16) is present in the +machine. + +There is further a TCM region register (search for "TCM Region +Registers" at the ARM site) that can report and modify the location +size of TCM memories at runtime. This is used to read out and modify +TCM location and size. Notice that this is not a MMU table: you +actually move the physical location of the TCM around. At the +place you put it, it will mask any underlying RAM from the +CPU so it is usually wise not to overlap any physical RAM with +the TCM. + +The TCM memory can then be remapped to another address again using +the MMU, but notice that the TCM if often used in situations where +the MMU is turned off. To avoid confusion the current Linux +implementation will map the TCM 1 to 1 from physical to virtual +memory in the location specified by the machine. + +TCM is used for a few things: + +- FIQ and other interrupt handlers that need deterministic + timing and cannot wait for cache misses. + +- Idle loops where all external RAM is set to self-refresh + retention mode, so only on-chip RAM is accessible by + the CPU and then we hang inside ITCM waiting for an + interrupt. + +- Other operations which implies shutting off or reconfiguring + the external RAM controller. + +There is an interface for using TCM on the ARM architecture +in <asm/tcm.h>. Using this interface it is possible to: + +- Define the physical address and size of ITCM and DTCM. + +- Tag functions to be compiled into ITCM. + +- Tag data and constants to be allocated to DTCM and ITCM. + +- Have the remaining TCM RAM added to a special + allocation pool with gen_pool_create() and gen_pool_add() + and provice tcm_alloc() and tcm_free() for this + memory. Such a heap is great for things like saving + device state when shutting off device power domains. + +A machine that has TCM memory shall select HAVE_TCM in +arch/arm/Kconfig for itself, and then the +rest of the functionality will depend on the physical +location and size of ITCM and DTCM to be defined in +mach/memory.h for the machine. Code that needs to use +TCM shall #include <asm/tcm.h> If the TCM is not located +at the place given in memory.h it will be moved using +the TCM Region registers. + +Functions to go into itcm can be tagged like this: +int __tcmfunc foo(int bar); + +Variables to go into dtcm can be tagged like this: +int __tcmdata foo; + +Constants can be tagged like this: +int __tcmconst foo; + +To put assembler into TCM just use +.section ".tcm.text" or .section ".tcm.data" +respectively. + +Example code: + +#include <asm/tcm.h> + +/* Uninitialized data */ +static u32 __tcmdata tcmvar; +/* Initialized data */ +static u32 __tcmdata tcmassigned = 0x2BADBABEU; +/* Constant */ +static const u32 __tcmconst tcmconst = 0xCAFEBABEU; + +static void __tcmlocalfunc tcm_to_tcm(void) +{ + int i; + for (i = 0; i < 100; i++) + tcmvar ++; +} + +static void __tcmfunc hello_tcm(void) +{ + /* Some abstract code that runs in ITCM */ + int i; + for (i = 0; i < 100; i++) { + tcmvar ++; + } + tcm_to_tcm(); +} + +static void __init test_tcm(void) +{ + u32 *tcmem; + int i; + + hello_tcm(); + printk("Hello TCM executed from ITCM RAM\n"); + + printk("TCM variable from testrun: %u @ %p\n", tcmvar, &tcmvar); + tcmvar = 0xDEADBEEFU; + printk("TCM variable: 0x%x @ %p\n", tcmvar, &tcmvar); + + printk("TCM assigned variable: 0x%x @ %p\n", tcmassigned, &tcmassigned); + + printk("TCM constant: 0x%x @ %p\n", tcmconst, &tcmconst); + + /* Allocate some TCM memory from the pool */ + tcmem = tcm_alloc(20); + if (tcmem) { + printk("TCM Allocated 20 bytes of TCM @ %p\n", tcmem); + tcmem[0] = 0xDEADBEEFU; + tcmem[1] = 0x2BADBABEU; + tcmem[2] = 0xCAFEBABEU; + tcmem[3] = 0xDEADBEEFU; + tcmem[4] = 0x2BADBABEU; + for (i = 0; i < 5; i++) + printk("TCM tcmem[%d] = %08x\n", i, tcmem[i]); + tcm_free(tcmem, 20); + } +} |