Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.
The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around. On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).
Where appropriate, an arch may override the generic storage facility and do
something different with the variable. On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.
Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions. Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller. A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.
I've build this code with allyesconfig for x86_64 and i386. I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.
This will affect all archs. Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:
struct pt_regs *old_regs = set_irq_regs(regs);
And put the old one back at the end:
set_irq_regs(old_regs);
Don't pass regs through to generic_handle_irq() or __do_IRQ().
In timer_interrupt(), this sort of change will be necessary:
- update_process_times(user_mode(regs));
- profile_tick(CPU_PROFILING, regs);
+ update_process_times(user_mode(get_irq_regs()));
+ profile_tick(CPU_PROFILING);
I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().
Some notes on the interrupt handling in the drivers:
(*) input_dev() is now gone entirely. The regs pointer is no longer stored in
the input_dev struct.
(*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does
something different depending on whether it's been supplied with a regs
pointer or not.
(*) Various IRQ handler function pointers have been moved to type
irq_handler_t.
Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
Some MMC hosts can only handle log2 block sizes. Unfortunately,
the MMC password support needs to be able to send non-log2 block
sizes. Provide a capability so that the MMC password support can
decide whether it should use this support or not.
The unfortunate side effect of this host limitation is that any
MMC card protected by a password which is not a log2 block size
can not be accessed on a host which only allows a log2 block size.
This change just adds the flag. The MMC password support code
needs updating to use it (if and when it is finally submitted.)
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Pavel Pisa
This is another approach to SDHC deficiency workaround.
It seems, that previous solution based on 16 bytes (FIFO length size)
read is still timing sensitive on genirq and fully preemptive kernels.
The new solution is backuped by M9328 UM statement, that only 512 byte
block are working properly and by 2.4.26 FreeScale's SDHC code.
Jay Monkman reports significant improvement on code based
on this driver after applying this change on MX21 as well.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The MMC specification allows non-power of two block sizes. As such,
we should not pass the log2 block size to host drivers, but instead
pass the byte size.
However, ARM MMCI can only work with log2 block size, so continue to
pass both the log2 block size and byte block size. This means that
for the moment, the byte block size must remain a power of two, but
this is the first stage of removing this restriction for other hosts.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Pavel Pisa
There has been problems that for some paths that clock are not stopped
during new command programming and initiation. Result is issuing
of incorrect command to the card. Some other problems are cleaned too.
Noisy report of known ERRATUM #4 has been suppressed.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Rather than having every driver duplicate the set_ios debugging,
provide a single version in mmc.c which can be expanded as we
add additional functionality.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Always send a stop command at the end of a data transfer. If we avoid
sending the stop command, some cards remain in data transfer mode, and
refuse to accept further read/write commands.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Pavel Pisa
The clock starting imxmci_start_clock() function contains hardware
issue workaround, which repeats start attempt, if SDHC does not react on
the first trial. But the second start attempt can be taken even, if the
first succeed and test code misses time limited clock running phase
due to delay caused by schedule to other task or some another device
interrupt. This change enables to detect such situation.
The performance is not issue, because usually at full clock rate
only about six loops in delay cycle are needed.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Pavel Pisa
This patch adds support of i.MX/MX1 SD/MMC controller.
It has been significantly redesigned from the original Sascha Hauer's
version to support scatter-gather DMA, to conform to latest Pierre Ossman's
and Russell King's MMC-SD Linux 2.6.x infrastructure.
The handling of all events has been moved to the softirq context
and is designed with no busy-looping in mind. Unfortunately
some controller bugs has to be overcome by limited looping
about 2-20 usec but these are observed only for initial card
recognition phase.
There are still some missing/missed IRQs problems under heavy load.
Help of somebody with access to the full SDHC design information
is probably necessary.
Regenerated against 2.6.16-git-060402 to solve clash with other patches.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
David Howells
Russell King
Pavel Pisa
Jörn Engel