If two requests have been submitted and one of them is running, if you
call pl330_chan_ctrl(ch_id, PL330_OP_START), there's a window of time
between the spin_lock_irqsave() and the _state() check in which the
running transaction may finish. In that case, we don't receive the
interrupt (because they are disabled), but _start() sees that the DMA
is stopped, so it starts it. The problem is that it sends the
transaction that has just finished again, because pl330_update()
hasn't mark it as done yet.
This patch fixes this race condition by not calling _start() if the
DMA is already executing transactions. When interrupts are reenabled,
pl330_update() will call _start().
Reference: <1317892206-3600-1-git-send-email-javi.merino@arm.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Acked-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The driver can handle different revisions of the core
which vary only minorly.
Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
PL330 is a configurable DMA controller PrimeCell device.
The register map of the device is well defined.
The configuration of a particular implementation can be
read from the six configuration registers CR0-4,Dn.
This patch implements a driver for the specification:-
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0424a/DDI0424A_dmac_pl330_r0p0_trm.pdf
The exported interface should be sufficient to implement
a driver for any DMA API.
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
