wwan: core: Support slicing in port TX flow of WWAN subsystem

wwan_port_fops_write inputs the SKB parameter to the TX callback of
the WWAN device driver. However, the WWAN device (e.g., t7xx) may
have an MTU less than the size of SKB, causing the TX buffer to be
sliced and copied once more in the WWAN device driver.

This patch implements the slicing in the WWAN subsystem and gives
the WWAN devices driver the option to slice(by frag_len) or not. By
doing so, the additional memory copy is reduced.

Meanwhile, this patch gives WWAN devices driver the option to reserve
headroom in fragments for the device-specific metadata.

Signed-off-by: haozhe chang <haozhe.chang@mediatek.com>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Link: https://lore.kernel.org/r/20230316095826.181904-1-haozhe.chang@mediatek.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: wwan: mhi_wwan_ctrl: Add DUN2 to have a secondary AT port

In order to have a secondary AT port add "DUN2".

Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Revert "bus: mhi: Add inbound buffers allocation flag"

This reverts commit 0092a1e3f7636ff4e202a41b0320690699247e22

This should be reverted in the char-misc-next branch to make merging
with Linus's branch possible due to issues with the mhi code that was
found in the networking tree.

Link: https://lore.kernel.org/r/20210827175852.GB15018@thinkpad
Reported-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bhaumik Bhatt <bbhatt@codeaurora.org>
Cc: Hemant Kumar <hemantk@codeaurora.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Loic Poulain <loic.poulain@linaro.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

bus: mhi: Add inbound buffers allocation flag

Currently, the MHI controller driver defines which channels should
have their inbound buffers allocated and queued. But ideally, this is
something that should be decided by the MHI device driver instead,
which actually deals with that buffers.

Add a flag parameter to mhi_prepare_for_transfer allowing to specify
if buffers have to be allocated and queued by the MHI stack.

Keep auto_queue flag for now, but should be removed at some point.

Link: https://lore.kernel.org/r/1624566520-20406-1-git-send-email-loic.poulain@linaro.org
Tested-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20210802051255.5771-2-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert "net: really fix the build..."

This reverts commit ce78ffa3ef1681065ba451cfd545da6126f5ca88.

Wren and Nicolas reported that ath11k was failing to initialise QCA6390
Wi-Fi 6 device with error:

qcom_mhi_qrtr: probe of mhi0_IPCR failed with error -22

Commit ce78ffa3ef16 ("net: really fix the build..."), introduced in
v5.14-rc5, caused this regression in qrtr. Most likely all ath11k
devices are broken, but I only tested QCA6390. Let's revert the broken
commit so that ath11k works again.

Reported-by: Wren Turkal <wt@penguintechs.org>
Reported-by: Nicolas Schichan <nschichan@freebox.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210826172816.24478-1-kvalo@codeaurora.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: wwan: mhi_wwan_ctrl: Fix possible deadlock

Lockdep detected possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&mhiwwan->rx_lock);
local_irq_disable();
lock(&mhi_cntrl->pm_lock);
lock(&mhiwwan->rx_lock);
<Interrupt>
lock(&mhi_cntrl->pm_lock);

*** DEADLOCK ***

To prevent this we need to disable the soft-interrupts when taking
the rx_lock.

Cc: stable@vger.kernel.org
Fixes: fa588eba632d ("net: Add Qcom WWAN control driver")
Reported-by: Thomas Perrot <thomas.perrot@bootlin.com>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: really fix the build...

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

net: wwan: mhi_wwan_ctrl: Fix RX buffer starvation

The mhi_wwan_rx_budget_dec function is supposed to return true if
RX buffer budget has been successfully decremented, allowing to queue
a new RX buffer for transfer. However the current implementation is
broken when RX budget is '1', in which case budget is decremented but
false is returned, preventing to requeue one buffer, and leading to
RX buffer starvation.

Fixes: fa588eba632d ("net: Add Qcom WWAN control driver")
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: wwan: Fix bit ops double shift

bit operation helpers such as test_bit, clear_bit, etc take bit
position as parameter and not value. Current usage causes double
shift => BIT(BIT(0)). Fix that in wwan_core and mhi_wwan_ctrl.

Fixes: 9a44c1cc6388 ("net: Add a WWAN subsystem")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: Add Qcom WWAN control driver

The MHI WWWAN control driver allows MHI QCOM-based modems to expose
different modem control protocols/ports via the WWAN framework, so that
userspace modem tools or daemon (e.g. ModemManager) can control WWAN
config and state (APN config, SMS, provider selection...). A QCOM-based
modem can expose one or several of the following protocols:
- AT: Well known AT commands interactive protocol (microcom, minicom...)
- MBIM: Mobile Broadband Interface Model (libmbim, mbimcli)
- QMI: QCOM MSM/Modem Interface (libqmi, qmicli)
- QCDM: QCOM Modem diagnostic interface (libqcdm)
- FIREHOSE: XML-based protocol for Modem firmware management
(qmi-firmware-update)

Note that this patch is mostly a rework of the earlier MHI UCI
tentative that was a generic interface for accessing MHI bus from
userspace. As suggested, this new version is WWAN specific and is
dedicated to only expose channels used for controlling a modem, and
for which related opensource userpace support exist.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>