ARM: OMAP3+: Implement timer workaround for errata i103 and i767

Errata Titles:
i103: Delay needed to read some GP timer, WD timer and sync timer
      registers after wakeup (OMAP3/4)
i767: Delay needed to read some GP timer registers after wakeup (OMAP5)

Description (i103/i767):
If a General Purpose Timer (GPTimer) is in posted mode
(TSICR [2].POSTED=1), due to internal resynchronizations, values read in
TCRR, TCAR1 and TCAR2 registers right after the timer interface clock
(L4) goes from stopped to active may not return the expected values. The
most common event leading to this situation occurs upon wake up from
idle.

GPTimer non-posted synchronization mode is not impacted by this
limitation.

Workarounds:
1). Disable posted mode
2). Use static dependency between timer clock domain and MPUSS clock
    domain
3). Use no-idle mode when the timer is active

Workarounds #2 and #3 are not pratical from a power standpoint and so
workaround #1 has been implemented. Disabling posted mode adds some CPU
overhead for configuring and reading the timers as the CPU has to wait
for accesses to be re-synchronised within the timer. However, disabling
posted mode guarantees correct operation.

Please note that it is safe to use posted mode for timers if the counter
(TCRR) and capture (TCARx) registers will never be read. An example of
this is the clock-event system timer. This is used by the kernel to
schedule events however, the timers counter is never read and capture
registers are not used. Given that the kernel configures this timer
often yet never reads the counter register it is safe to enable posted
mode in this case. Hence, for the timer used for kernel clock-events,
posted mode is enabled by overriding the errata for devices that are
impacted by this defect.

For drivers using the timers that do not read the counter or capture
registers and wish to use posted mode, can override the errata and
enable posted mode by making the following function calls.

	__omap_dm_timer_override_errata(timer, OMAP_TIMER_ERRATA_I103_I767);
	__omap_dm_timer_enable_posted(timer);

Both dmtimers and watchdogs are impacted by this defect this patch only
implements the workaround for the dmtimer. Currently the watchdog driver
does not read the counter register and so no workaround is necessary.

Posted mode will be disabled for all OMAP2+ devices (including AM33xx)
using a GP timer as a clock-source timer to guarantee correct operation.
This is not necessary for OMAP24xx devices but the default clock-source
timer for OMAP24xx devices is the 32k-sync timer and not the GP timer
and so should not have any impact. This should be re-visited for future
devices if this errata is fixed.

Confirmed with Vaibhav Hiremath that this bug also impacts AM33xx
devices.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Fix timer posted mode support

Currently the dmtimer posted mode is being enabled when the function
omap_dm_timer_enable_posted() is called. This function is only being called
for OMAP1 timers and OMAP2+ timers that are being used as system timers. Hence,
for OMAP2+ timers that are NOT being used as a system timer, posted mode is
not enabled but the "timer->posted" variable is still set (incorrectly) in
the omap_dm_timer_prepare() function.

This is a regression introduced by commit 3392cdd3 (ARM: OMAP: dmtimer:
switch-over to platform device driver) which was before the
omap_dm_timer_enable_posted() function was introduced. Although this is a
regression from the original code it only impacts performance and so is not
needed for stable.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP3: Correct HWMOD DMTIMER SYSC register declarations

Currently, the OMAP3 HWMOD data defines two TIOCP_CFG register structures
(referred to as the SYSC register in the HWMOD data) where timers 1, 2 and 10
use one of the defintions and the other timers use the other definition. For
OMAP3 devices the structure of the DMTIMER TIOCP_CFG register is the same for
all 12 instances of the DMTIMER. Please note that this is a difference between
OMAP3 and OMAP4 and could be the source of the confusion.

For OMAP3 devices, the DMTIMER TIOCP_CFG register has the fields,
clock-activity, emufree, idlemode, enwakeup, softreset and autoidle for all
12 timers. Therefore, remove one of the SYSC register definitions for the
DMTIMERs and ensure the appropriate register fields are defined for all
DMTIMERs.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP2/3: Define HWMOD software reset status for DMTIMERs

For OMAP2/3 devices, the HWMOD data does not define a software reset status
field for the DMTIMERs. Therefore, when HWMOD performs a soft-reset of the
DMTIMER we don't check and wait for the reset to complete. For OMAP2/3 devices,
the software reset status for a DMTIMER can be read from bit 0 of the DMTIMER
TISTAT register (referred to as the SYSS register in HWMOD). Add the
appropriate HWMOD definitions so that HWMOD will check the software reset
status when performing a software reset of the DMTIMER.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP2+: Don't use __omap_dm_timer_reset()

Currently OMAP2+ devices are using the function __omap_dm_timer_reset() to
configure the clock-activity, idle, wakeup-enable and auto-idle fields in the
timer OCP_CFG register. The name of the function is mis-leading because this
function does not actually perform a reset of the timer.

For OMAP2+ devices, HWMOD is responsible for reseting and configuring the
timer OCP_CFG register. Therefore, do not use __omap_dm_timer_reset() for
OMAP2+ devices and rely on HWMOD. Furthermore, some timer instances do not
have the fields clock-activity, wakeup-enable and auto-idle and so this
function could configure the OCP_CFG register incorrectly.

Currently HWMOD is not configuring the clock-activity field in the OCP_CFG
register for timers that have this field. Commit 0f0d080 (ARM: OMAP: DMTimer:
Use posted mode) configures the clock-activity field to keep the f-clk enabled
so that the wake-up capability is enabled. Therefore, add the appropriate flags
to the timer HWMOD structures to configure this field in the same way.

For OMAP2/3 devices all dmtimers have the clock-activity field, where as for
OMAP4 devices, only dmtimer 1, 2 and 10 have the clock-activity field.

Verified on OMAP2420 H4, OMAP3430 Beagle and OMAP4430 Panda that HWMOD is
configuring the dmtimer OCP_CFG register as expected for clock-events timer.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Fix dmtimer reset for timer1

In commit e32f7ec2 (ARM: OMAP: Fix 32 kHz timer and modify GP timer to use GPT1)
a fix was added to prevent timer1 being reset in the function
omap_dm_timer_reset() because timer1 was being used as the system timer for
OMAP2 devices. Although timer1 is still used by most OMAP2+ devices as a system
timer, the function omap_dm_timer_reset() is now only being called for OMAP1
devices and OMAP1 does not use timer1 as a system timer. Therefore, remove the
check in omap_dm_timer_reset() so that timer1 is reset for OMAP1 devices.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Don't restore of DMTIMER TISTAT register

The timer TISTAT register is a read-only register and therefore restoring the
context is not needed. Furthermore, the context of TISTAT is never saved
anywhere in the current code. The TISTAT register is read-only for all OMAP
devices from OMAP1 to OMAP4. OMAP5 timers no longer have this register.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Don't restore DMTIMER interrupt status register

Restoring the timer interrupt status is not possible because writing a 1 to any
bit in the register clears that bit if set and writing a 0 has no affect.
Furthermore, if an interrupt is pending when someone attempts to disable a
timer, the timer will fail to transition to the idle state and hence it's
context will not be lost. Users should take care to service all interrupts
before disabling the timer.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Fix spurious interrupts when using timer match feature

The OMAP DMTIMERs can generate an interrupt when the timer counter value
matches the value stored in the timer's match register. When using this
feature spurious interrupts were seen, because the compare logic is being
enabled before the match value is loaded and according to the documentation
the match value must be loaded before the compare logic is enable.

The reset value for the timer counter and match registers is 0 and hence,
by enabling the compare logic before the actual match value is loaded a
spurious interrupt can be generated as the reset values match.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Add dmtimer interrupt disable function

The OMAP dmtimer driver does not currently have a function to disable the
timer interrupts. For some timer instances the timer interrupt enable
function can be used to disable the interrupts because the same interrupt
enable register is used to disable interrupts. However, some timer instances
have separate interrupt enable/disable registers and so this will not work.
Therefore, add a dedicated function to disable interrupts.

This change is required for OMAP4+ devices. For OMAP4, all timers apart from 1,
2 and 10 need this function and for OMAP5 all timers need this function.
Please note that the interrupt disable function has been written so that it
can be used by all OMAP devices.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Remove unnecessary call to clk_get()

Whenever we call the function omap_dm_timer_set_source() to set the clock
source of a dmtimer we look-up the dmtimer functional clock source by
calling clk_get(). This is not necessary because on requesting a dmtimer
we look-up the functional clock source and store it in the omap_dm_timer
structure. So instead of looking up the clock again used the clock handle
that stored in the omap_dm_timer structure.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
ARM: OMAP: Remove __omap_dm_timer_set_source function

The __omap_dm_timer_set_source() function is only used by the system timer
(clock-events and clock-source) code for OMAP2+ devices. Therefore, we can
remove this code from the dmtimer driver and move it to the system timer
code for OMAP2+ devices.

The current __omap_dm_timer_set_source() function calls clk_disable() before
calling clk_set_parent() and clk_enable() afterwards. We can avoid these calls
to clk_disable/enable by moving the calls to omap_hwmod_setup_one() and
omap_hwmod_enable() to after the call to clk_set_parent() in
omap_dm_timer_init_one().

The function omap_hwmod_setup_one() will enable the timers functional clock
and therefore increment the use-count of the functional clock to 1.
clk_set_parent() will fail if the use-count is not 0 when called. Hence, if
omap_hwmod_setup_one() is called before clk_set_parent(), we will need to call
clk_disable() before calling clk_set_parent() to decrement the use-count.
Hence, avoid these extra calls to disable and enable the functional clock by
moving the calls to omap_hwmod_setup_one() and omap_hwmod_enable() to after
clk_set_parent().

We can also remove the delay from the __omap_dm_timer_set_source() function
because enabling the clock will now be handled via the HWMOD framework by
calling omap_hwmod_setup_one(). Therefore, by moving the calls to
omap_hwmod_setup_one() and omap_hwmod_enable() to after the call to
clk_set_parent(), we can simply replace __omap_dm_timer_set_source() with
clk_set_parent().

It should be safe to move these hwmod calls to later in the
omap_dm_timer_init_one() because other calls to the hwmod layer that occur
before are just requesting resource information.

Testing includes boot testing on OMAP2420 H4, OMAP3430 SDP and OMAP4430 Blaze
with the following configurations:
1. CONFIG_OMAP_32K_TIMER=y
2. CONFIG_OMAP_32K_TIMER=y and boot parameter "clocksource=gp_timer"
3. CONFIG_OMAP_32K_TIMER not set
4. CONFIG_OMAP_32K_TIMER not set and boot parameter "clocksource=gp_timer"

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>