Revision 497d2214e5ba58ef55025b9951e7f9cccab760e4 authored by Mike Turquette on 06 January 2014, 05:36:43 UTC, committed by Mike Turquette on 06 January 2014, 05:36:43 UTC
Samsung Clock fixes for 3.13-rc7
* Several patches fixing up incorrectly defined register addresses and
bitfield offsets that could lead to undefined operation when accessing
respective registers or bitfields.
1) clk: exynos5250: fix sysmmu_mfc{l,r} gate clocks
2a) clk: samsung: exynos5250: Fix ACP gate register offset
2b) clk: samsung: exynos5250: Add MDMA0 clocks
2c) ARM: dts: exynos5250: Fix MDMA0 clock number
3) clk: samsung: exynos4: Correct SRC_MFC register
All three issues have been present since Exynos5250 and Exynos4 clock
drivers were added by commits 6e3ad26816b72 ("clk: exynos5250:
register clocks using common clock framework") and e062b571777f5
("clk: exynos4: register clocks using common clock framework")
respectively.
* Patch to fix automatic disabling of Exynos5250 sysreg clock that could
cause undefined operation of several peripherals, such as USB, I2C,
MIPI or display block.
4) clk: samsung: exynos5250: Add CLK_IGNORE_UNUSED flag for the sysreg
clock
Present since Exynos5250 clock drivers was added by commits
6e3ad26816b72 ("clk: exynos5250: register clocks using common clock
framework").
* Patch fixing compilation warning in clk-exynos-audss driver when
CONFIG_PM_SLEEP is disabled.
5) clk: exynos: File scope reg_save array should depend on PM_SLEEP
Present since the driver was added by commit 1241ef94ccc3 ("clk:
samsung: register audio subsystem clocks using common clock
framework").
io_ordering.txt
On some platforms, so-called memory-mapped I/O is weakly ordered. On such
platforms, driver writers are responsible for ensuring that I/O writes to
memory-mapped addresses on their device arrive in the order intended. This is
typically done by reading a 'safe' device or bridge register, causing the I/O
chipset to flush pending writes to the device before any reads are posted. A
driver would usually use this technique immediately prior to the exit of a
critical section of code protected by spinlocks. This would ensure that
subsequent writes to I/O space arrived only after all prior writes (much like a
memory barrier op, mb(), only with respect to I/O).
A more concrete example from a hypothetical device driver:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
...
In the case above, the device may receive newval2 before it receives newval,
which could cause problems. Fixing it is easy enough though:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: (void)readl(safe_register); /* maybe a config register? */
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: (void)readl(safe_register); /* maybe a config register? */
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
Here, the reads from safe_register will cause the I/O chipset to flush any
pending writes before actually posting the read to the chipset, preventing
possible data corruption.
Computing file changes ...
