This patch adds a new rate rounding algorithm for DPLL clocks on the
OMAP2/3 architecture.
For a desired DPLL target rate, there may be several
multiplier/divider (M, N) values which will generate a sufficiently
close rate. Lower N values result in greater power economy. However,
lower N values can cause the difference between the rounded rate and
the target rate ("rate error") to be larger than it would be with a
higher N. This can cause downstream devices to run more slowly than
they otherwise would.
This DPLL rate rounding algorithm:
- attempts to find the lowest possible N (DPLL divider) to reach the
target_rate (since, according to Richard Woodruff <r-woodruff@ti.com>,
lower N values save more power than higher N values).
- allows developers to set an upper bound on the error between the
rounded rate and the desired target rate ("rate tolerance"), so an
appropriate balance between rate fidelity and power savings can be
set. This maximum rate error tolerance is set via
omap2_set_dpll_rate_tolerance().
- never returns a rounded rate higher than the target rate.
The rate rounding algorithm caches the last rounded M, N, and rate
computation to avoid rounding the rate twice for each clk_set_rate()
call. (This patch does not yet implement set_rate for DPLLs; that
follows in a future patch.)
The algorithm trades execution speed for rate accuracy. It will find
the (M, N) set that results in the least rate error, within a
specified rate tolerance. It does this by evaluating each divider
setting - on OMAP3, this involves 128 steps. Another approach to DPLL
rate rounding would be to bail out as soon as a valid rate is found
within the rate tolerance, which would trade rate accuracy for
execution speed. Alternate implementations welcome.
This code is not yet used by the OMAP24XX DPLL clock, since it
is currently defined as a composite clock, fusing the DPLL M,N and the
M2 output divider. This patch also renames the existing OMAP24xx DPLL
programming functions to highlight that they program both the DPLL and
the DPLL's output multiplier.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This patch adds support for DPLL autoidle control to the OMAP3 clock
framework. These functions will be used by the noncore DPLL enable
and disable code - this is because, according to the CDP code, the
DPLL autoidle status must be saved and restored across DPLL
lock/bypass/off transitions.
N.B.: the CORE DPLL (DPLL3) has three autoidle mode options, rather
than just two. This code currently does not support the third option,
low-power bypass autoidle.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This patch adds support for mach-omap2 based on current
mcbsp platform driver.
Signed-off-by: Eduardo Valentin <eduardo.valentin@indt.org.br>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This patch removes following message on dpll5_m2_ck enable and
disable:
clock.c: Enable for dpll5_m2_ck without enable code
clock: clk_disable called on independent clock dpll5_m2_ck
which has no enable_reg
Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
ssi_l4_ick should have PARENT_CONTROLS_CLOCK flag.
ST_SSI_STDBY bit in idlest register cannot be used in omap2_clk_wait_ready
Signed-off-by: Jouni Högander <jouni.hogander@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Wrong shift values were used for gpio2-6 fclks (gpt2-6 shift).
Signed-off-by: Jouni Högander <jouni.hogander@nokia.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
These changes is the result of the discussion with Paul Walmsley.
His ideas are included into this patch.
Remove DPLL output divider handling from DPLLs and CLKOUTX2 clocks,
and place it into specific DPLL output divider clocks (e.g., dpll3_m2_clk).
omap2_get_dpll_rate() now returns the correct DPLL rate, as represented
by the DPLL's CLKOUT output. Also add MPU and IVA2 subsystem clocks, along
with high-frequency bypass support.
Add support for DPLLs function in locked and bypass clock modes.
Signed-off-by: Roman Tereshonkov <roman.tereshonkov@nokia.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
