net: mvneta: replace Tx timer with a real interrupt

Right now the mvneta driver doesn't handle Tx IRQ, and relies on two
mechanisms to flush Tx descriptors : a flush at the end of mvneta_tx()
and a timer. If a burst of packets is emitted faster than the device
can send them, then the queue is stopped until next wake-up of the
timer 10ms later. This causes jerky output traffic with bursts and
pauses, making it difficult to reach line rate with very few streams.

A test on UDP traffic shows that it's not possible to go beyond 134
Mbps / 12 kpps of outgoing traffic with 1500-bytes IP packets. Routed
traffic tends to observe pauses as well if the traffic is bursty,
making it even burstier after the wake-up.

It seems that this feature was inherited from the original driver but
nothing there mentions any reason for not using the interrupt instead,
which the chip supports.

Thus, this patch enables Tx interrupts and removes the timer. It does
the two at once because it's not really possible to make the two
mechanisms coexist, so a split patch doesn't make sense.

First tests performed on a Mirabox (Armada 370) show that less CPU
seems to be used when sending traffic. One reason might be that we now
call the mvneta_tx_done_gbe() with a mask indicating which queues have
been done instead of looping over all of them.

The same UDP test above now happily reaches 987 Mbps / 87.7 kpps.
Single-stream TCP traffic can now more easily reach line rate. HTTP
transfers of 1 MB objects over a single connection went from 730 to
840 Mbps. It is even possible to go significantly higher (>900 Mbps)
by tweaking tcp_tso_win_divisor.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Arnaud Ebalard <arno@natisbad.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: remove tests for impossible cases in the tx_done path

Currently, mvneta_txq_bufs_free() calls mvneta_tx_done_policy() with
a non-null cause to retrieve the pointer to the next queue to process.
There are useless tests on the return queue number and on the pointer,
all of which are well defined within a known limited set. This code
path is fast, although not critical. Removing 3 tests here that the
compiler could not optimize (verified) is always desirable.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: factor rx refilling code

Make mvneta_rxq_fill() use mvneta_rx_refill() instead of using
duplicate code.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: simplify access to the rx descriptor status

At several places, we already know the value of the rx status but
we call functions which dereference the pointer again to get it
and don't need the descriptor for anything else. Simplify this
task by replacing the rx desc pointer by the status word itself.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: prefetch next rx descriptor instead of current one

Currently, the mvneta driver tries to prefetch the current Rx
descriptor during read. Tests have shown that prefetching the
next one instead increases general performance by about 1% on
HTTP traffic.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: convert to build_skb()

Make use of build_skb() to allocate frags on the RX path. When frag size
is lower than a page size, we can use netdev_alloc_frag(), and we fall back
to kmalloc() for larger sizes. The frag size is stored into the mvneta_port
struct. The alloc/free functions check the frag size to decide what alloc/
free method to use. MTU changes are safe because the MTU change function
stops the device and clears the queues before applying the change.

With this patch, I observed a reproducible 2% performance improvement on
HTTP-based benchmarks, and 5% on small packet RX rate.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: implement rx_copybreak

calling dma_map_single()/dma_unmap_single() is quite expensive compared
to copying a small packet. So let's copy short frames and keep the buffers
mapped. We set the limit to 256 bytes which seems to give good results both
on the XP-GP board and on the AX3/4.

The Rx small packet rate increased by 16.4% doing this, from 486kpps to
573kpps. It is worth noting that even the call to the function
dma_sync_single_range_for_cpu() is expensive (300 ns) although less
than dma_unmap_single(). Without it, the packet rate raises to 711kpps
(+24% more). Thus on systems where coherency from device to CPU is
guaranteed by a snoop control unit, this patch should provide even more
gains, and probably rx_copybreak could be increased.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: mvneta_tx_done_gbe() cleanups

mvneta_tx_done_gbe() return value and third parameter are no more
used. This patch changes the function prototype and removes a useless
variable where the function is called.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: mvneta: make mvneta_txq_done() return void

The function return parameter is not used in mvneta_tx_done_gbe(),
where the function is called. This patch makes the function return
void.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Merge branch 'mvneta'

Willy Tarreau says:

====================
Assorted mvneta fixes and improvements

this series provides some fixes for a number of issues met with the
mvneta driver, then adds some improvements. Patches 1-5 are fixes
and would be needed in 3.13 and likely -stable. The next ones are
performance improvements and cleanups :

  - driver lockup when reading stats while sending traffic from multiple
    CPUs : this obviously only happens on SMP and is the result of missing
    locking on the driver. The problem was present since the introduction
    of the driver in 3.8. The first patch performs some changes that are
    needed for the second one which actually fixes the issue by using
    per-cpu counters. It could make sense to backport this to the relevant
    stable versions.

  - mvneta_tx_timeout calls various functions to reset the NIC, and these
    functions sleep, which is not allowed here, resulting in a panic.
    Better completely disable this Tx timeout handler for now since it is
    never called. The problem was encountered while developing some new
    features, it's uncertain whether it's possible to reproduce it with
    regular usage, so maybe a backport to stable is not needed.

  - replace the Tx timer with a real Tx IRQ. As first reported by Arnaud
    Ebalard and explained by Eric Dumazet, there is no way this driver
    can work correctly if it uses a driver to recycle the Tx descriptors.
    If too many packets are sent at once, the driver quickly ends up with
    no descriptors (which happens twice as easily in GSO) and has to wait
    10ms for recycling its descriptors and being able to send again. Eric
    has worked around this in the core GSO code. But still when routing
    traffic or sending UDP packets, the limitation is very visible. Using
    Tx IRQs allows Tx descriptors to be recycled when sent. The coalesce
    value is still configurable using ethtool. This fix turns the UDP
    send bitrate from 134 Mbps to 987 Mbps (ie: line rate). It's made of
    two patches, one to add the relevant bits from the original Marvell's
    driver, and another one to implement the change. I don't know if it
    should be backported to stable, as the bug only causes poor performance.

  - Patches 6..8 are essentially cleanups, code deduplication and minor
    optimizations for not re-fetching a value we already have (status).

  - patch 9 changes the prefetch of Rx descriptor from current one to
    next one. In benchmarks, it results in about 1% general performance
    increase on HTTP traffic, probably because prefetching the current
    descriptor does not leave enough time between the start of prefetch
    and its usage.

  - patch 10 implements support for build_skb() on Rx path. The driver
    now preallocates frags instead of skbs and builds an skb just before
    delivering it. This results in a 2% performance increase on HTTP
    traffic, and up to 5% on small packet Rx rate.

  - patch 11 implements rx_copybreak for small packets (256 bytes). It
    avoids a dma_map_single()/dma_unmap_single() and increases the Rx
    rate by 16.4%, from 486kpps to 573kpps. Further improvements up to
    711kpps are possible depending how the DMA is used.

  - patches 12 and 13 are extra cleanups made possible by some of the
    simplifications above.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: support max-speed device tree property

This patch adds support to "max-speed" property which is a standard
Ethernet device tree property. max-speed specifies maximum speed
(specified in megabits per second) supported the device.

Depending on the clocking schemes some of the boards can only support
few link speeds, so having a way to limit the link speed in the mac
driver would allow such setups to work reliably.

Without this patch there is no way to tell the driver to limit the
link speed.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: mdio: remove reset gpio free

This patch removes gpio_free for reset line of the phy, driver stores
the gpio number in its private data-structure to use in future. As the
driver uses this pin in future this pin should not be freed.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: move dma allocation to new function

This patch moves dma resource allocation to a new function
alloc_dma_desc_resources, the reason for moving this to a new function
is to keep the memory allocations in a separate function. One more reason
it to get suspend and hibernation cases working without releasing and
allocating these resources during suspend-resume and freeze-restore
cases.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: move hardware setup for stmmac_open to new function

This patch moves hardware setup part of the code in stmmac_open to a new
function stmmac_hw_setup, the reason for doing this is to make hw
initialization independent function so that PM functions can re-use it to
re-initialize the IP after returning from low power state.
This will also avoid code duplication across stmmac_resume/restore and
stmmac_open.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: make stmmac_mdio_reset non-static

This patch promotes stmmac_mdio_reset function from static to
non-static, so that power management functions can decide to reset if
the IP comes out from lowe power state specially hibernation cases.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: fix power management suspend-resume case

The driver PM resume assumes that the IP is still powered up and the
all the register contents are not disturbed when it comes out of low
power suspend case. This assumption is wrong, basically the driver
should not consider any state of registers after it comes out of low
power. However driver can keep the part of the IP powered up if its a
wake up source. But it can not assume the register state of the IP. Also
its possible that SOC glue layer can take the power off the IP if its
not wake-up source to reduce the power consumption.

This patch re initializes hardware by calling stmmac_hw_setup function in
resume case.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: use suspend functions for hibernation

In hibernation freeze case the driver just releases the resources like
dma buffers, irqs, unregisters the drivers and during restore it does
register, request the resources. This is not really necessary, as part
of power management all the data structures are intact, all the
previously allocated resources can be used after coming out of low
power.

This patch uses the suspend and resume callbacks for freeze and
restore which initializes the hardware correctly without unregistering
or releasing the resources, this should also help in reducing the time
to restore.

Also this patch fixes a bug in stmmac_pltfr_restore and
stmmac_pltfr_freeze where it tries to get hold of platform data via
dev_get_platdata call, which would return NULL in device tree cases and
the next if statement would crash as there is no NULL check.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: restore pinstate in pm resume.

This patch adds code to restore default pinstate of the pins when it
comes back from low power state. Without this patch the state of the
pins would be unknown and the driver would not work.

This patch also adds code to put the pins in to sleep state when the
driver enters low power state.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: stmmac: notify the PM core of a wakeup event.

In PM_SUSPEND_FREEZE and WOL(Wakeup On Lan) case, when the driver gets a
wakeup event, either the driver or platform specific PM code should notify
the pm core about it, so that the system can wakeup from low power.

In cases where there is no involvement of platform specific PM, it
becomes driver responsibility to notify the PM core to wakeup the
system.

Without this WOL with PM_SUSPEND_FREEZE does not work on STi based SOCs.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Merge branch 'stmmac_pm'

Srinivas Kandagatla says:

====================
net: stmmac PM related fixes.

During PM_SUSPEND_FREEZE testing, I have noticed that PM support in STMMAC is
partly broken. I had to re-arrange the code to do PM correctly. There were lot
of things I did not like personally and some bits did not work in the first
place. I thought this is the nice opportunity to clean the mess up.

Here is what I did:
 any
1> Test PM suspend freeze via pm_test
It did not work for following reasons.
 - If the power to gmac is removed when it enters in low power state.
stmmac_resume could not cope up with such behaviour, it was expecting the ip
register contents to be still same as before entering low power, This
assumption is wrong. So I started to add some code to do Hardware
initialization, thats when I started to re-arrange the code. stmmac_open
contains both resource and memory allocations and hardware initialization. I
had to separate these two things in two different functions.

These two patches do that
  net: stmmac: move dma allocation to new function
  net: stmmac: move hardware setup for stmmac_open to new function

And rest of the other patches are fixing the loose ends, things like mdio
reset, which might be necessary in cases likes hibernation(I did not test).

In hibernation cases the driver was just unregistering with subsystems and
releasing resources which I did not like and its not necessary to do this as
part of PM. So using the same stmmac_suspend/resume made more sense for
hibernation cases than using stmmac_open/release.
Also fixed a NULL pointer dereference bug too.

2> Test WOL via PM_SUSPEND_FREEZE
Did get an wakeup interrupt, but could not wakeup a freeze system.
So I had to add pm_wakeup_event to the driver.
net: stmmac: notify the PM core of a wakeup event. patch.

Also few patches like
  net: stmmac: make stmmac_mdio_reset non-static
  net: stmmac: restore pinstate in pm resume.
helps the resume function to reset the phy and put back the pins in default
state.

Changes since RFC:
	- Rebased to net-next on Dave's suggestion.

All these patches are Acked by Peppe.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>