c_can uses overlay structure for accessing c_can module registers.
With this kind of implementation it is difficult to add one more ip
which is similar to c_can in functionality but different register
offsets.

This patch changes the overlay structure implementation to an array
with register offset as index. This way we can overcome the above
limitation.
Signed-off-by: NAnilKumar Ch <anilkumar@ti.com>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

This patch fixes an interrupt thrash issue with c_can driver.

In c_can_isr() function interrupts are disabled and enabled only in
c_can_poll() function. c_can_isr() & c_can_poll() both read the
irqstatus flag. However, irqstatus is always read as 0 in c_can_poll()
because all C_CAN interrupts are disabled in c_can_isr(). This causes
all interrupts to be re-enabled in c_can_poll() which in turn causes
another interrupt since the event is not really handled. This keeps
happening causing a flood of interrupts.

To fix this, read the irqstatus register in isr and use the same cached
value in the poll function.

Cc: stable@kernel.org # 2.6.39+
Signed-off-by: NAnilKumar Ch <anilkumar@ti.com>
Acked-by: NWolfgang Grandegger <wg@grandegger.com>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

Bosch C_CAN controller is a full-CAN implementation which is compliant
to CAN protocol version 2.0 part A and B. Bosch C_CAN user manual can be
obtained from:

http://www.semiconductors.bosch.de/media/en/pdf/ipmodules_1/c_can/users_manual_c_can.pdf

This patch adds the support for this controller.
The following are the design choices made while writing the controller
driver:
1. Interface Register set IF1 has be used only in the current design.
2. Out of the 32 Message objects available, 16 are kept aside for RX
   purposes and the rest for TX purposes.
3. NAPI implementation is such that both the TX and RX paths function
   in polling mode.
Signed-off-by: NBhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>