Date:   Mon, 7 Mar 2022 06:00:30 +0300
From:   Sergey Ryazanov <ryazanov.s.a@...il.com>
To:     Ricardo Martinez <ricardo.martinez@...ux.intel.com>
Cc:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Johannes Berg <johannes@...solutions.net>,
        Loic Poulain <loic.poulain@...aro.org>,
        M Chetan Kumar <m.chetan.kumar@...el.com>,
        chandrashekar.devegowda@...el.com,
        Intel Corporation <linuxwwan@...el.com>,
        chiranjeevi.rapolu@...ux.intel.com,
        Haijun Liu (刘海军) 
        <haijun.liu@...iatek.com>, amir.hanania@...el.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        dinesh.sharma@...el.com, eliot.lee@...el.com,
        ilpo.johannes.jarvinen@...el.com, moises.veleta@...el.com,
        pierre-louis.bossart@...el.com, muralidharan.sethuraman@...el.com,
        Soumya.Prakash.Mishra@...el.com, sreehari.kancharla@...el.com,
        madhusmita.sahu@...el.com
Subject: Re: [PATCH net-next v5 00/13] net: wwan: t7xx: PCIe driver for
 MediaTek M.2 modem

Hello Ricardo,

On Thu, Feb 24, 2022 at 1:35 AM Ricardo Martinez
<ricardo.martinez@...ux.intel.com> wrote:
> t7xx is the PCIe host device driver for Intel 5G 5000 M.2 solution which
> is based on MediaTek's T700 modem to provide WWAN connectivity.
> The driver uses the WWAN framework infrastructure to create the following
> control ports and network interfaces:
> * /dev/wwan0mbim0 - Interface conforming to the MBIM protocol.
>   Applications like libmbim [1] or Modem Manager [2] from v1.16 onwards
>   with [3][4] can use it to enable data communication towards WWAN.
> * /dev/wwan0at0 - Interface that supports AT commands.
> * wwan0 - Primary network interface for IP traffic.
>
> The main blocks in t7xx driver are:
> * PCIe layer - Implements probe, removal, and power management callbacks.
> * Port-proxy - Provides a common interface to interact with different types
>   of ports such as WWAN ports.
> * Modem control & status monitor - Implements the entry point for modem
>   initialization, reset and exit, as well as exception handling.
> * CLDMA (Control Layer DMA) - Manages the HW used by the port layer to send
>   control messages to the modem using MediaTek's CCCI (Cross-Core
>   Communication Interface) protocol.
> * DPMAIF (Data Plane Modem AP Interface) - Controls the HW that provides
>   uplink and downlink queues for the data path. The data exchange takes
>   place using circular buffers to share data buffer addresses and metadata
>   to describe the packets.
> * MHCCIF (Modem Host Cross-Core Interface) - Provides interrupt channels
>   for bidirectional event notification such as handshake, exception, PM and
>   port enumeration.
>
> The compilation of the t7xx driver is enabled by the CONFIG_MTK_T7XX config
> option which depends on CONFIG_WWAN.
> This driver was originally developed by MediaTek. Intel adapted t7xx to
> the WWAN framework, optimized and refactored the driver source code in close
> collaboration with MediaTek. This will enable getting the t7xx driver on the
> Approved Vendor List for interested OEM's and ODM's productization plans
> with Intel 5G 5000 M.2 solution.
>
> List of contributors:
> Amir Hanania <amir.hanania@...el.com>
> Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Chandrashekar Devegowda <chandrashekar.devegowda@...el.com>
> Dinesh Sharma <dinesh.sharma@...el.com>
> Eliot Lee <eliot.lee@...el.com>
> Haijun Liu <haijun.liu@...iatek.com>
> M Chetan Kumar <m.chetan.kumar@...el.com>
> Mika Westerberg <mika.westerberg@...ux.intel.com>
> Moises Veleta <moises.veleta@...el.com>
> Pierre-louis Bossart <pierre-louis.bossart@...el.com>
> Chiranjeevi Rapolu <chiranjeevi.rapolu@...el.com>
> Ricardo Martinez <ricardo.martinez@...ux.intel.com>
> Madhusmita Sahu <madhusmita.sahu@...el.com>
> Muralidharan Sethuraman <muralidharan.sethuraman@...el.com>
> Soumya Prakash Mishra <Soumya.Prakash.Mishra@...el.com>
> Sreehari Kancharla <sreehari.kancharla@...el.com>
> Suresh Nagaraj <suresh.nagaraj@...el.com>
>
> [1] https://www.freedesktop.org/software/libmbim/
> [2] https://www.freedesktop.org/software/ModemManager/
> [3] https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/582
> [4] https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/523
>
> v5:
> - Update Intel's copyright years to 2021-2022.
> - Remove circular dependency between DPMAIF HW (07) and HIF (08).
> - Keep separate patches for CLDMA (02) and Core (03)
>   but improve the code split by decoupling CLDMA from
>   modem ops and cleaning up t7xx_common.h.
> - Rename ID_CLDMA0/ID_CLDMA1 to CLDMA_ID_AP/CLDMA_ID_MD.
> - Consistently use CLDMA's ring_lock to protect tr_ring.
> - Free resources first and then print messages.
> - Implement suggested name changes.
> - Do not explicitly include dev_printk.h.
> - Remove redundant dev_err()s.
> - Fix possible memory leak during probe.
> - Remove infrastructure for legacy interrupts.
> - Remove unused macros and variables, including those that
>   can be replaced with constants.
> - Remove PCIE_MAC_MSIX_MSK_SET macro which is duplicated code.
> - Refactor __t7xx_pci_pm_suspend() for clarity.
> - Refactor t7xx_cldma_rx_ring_init() and t7xx_cldma_tx_ring_init().
> - Do not use & for function callbacks.
> - Declare a structure to access skb->cb[] data.
> - Use skb_put_data instead of memcpy.
> - No need to use kfree_sensitive.
> - Use dev_kfree_skb() instead of kfree_skb().
> - Refactor t7xx_prepare_device_rt_data() to remove potential leaks,
>   avoid unneeded memset and keep rt_data and packet_size updates
>   inside the same 'if' block.
> - Set port's rx_length_th back to 0 during uninit.
> - Remove unneeded 'blocking' parameter from t7xx_cldma_send_skb().
> - Return -EIO in t7xx_cldma_send_skb() if the queue is inactive.
> - Refactor t7xx_cldma_qs_are_active() to use pci_device_is_present().
> - Simplify t7xx_cldma_stop_q() and rename it to t7xx_cldma_stop_all_qs().
> - Fix potential leaks in t7xx_cldma_init().
> - Improve error handling in fsm_append_event and fsm_routine_starting().
> - Propagate return codes from fsm_append_cmd() and t7xx_fsm_append_event().
> - Refactor fsm_wait_for_event() to avoid unnecessary sleep.
> - Create the WWAN ports and net device only after the modem is in
>   the ready state.
> - Refactor t7xx_port_proxy_recv_skb() and port_recv_skb().
> - Rename t7xx_port_check_rx_seq_num() as t7xx_port_next_rx_seq_num()
>   and fix the seq_num logic to handle overflows.
> - Declare seq_nums as u16 instead of short.
> - Use unsigned int for local indexes.
> - Use min_t instead of the ternary operator.
> - Refactor the loop in t7xx_dpmaif_rx_data_collect() to avoid a dead
>   condition check.
> - Use a bitmap (bat_bitmap) instead of an array to keep track of
>   the DRB status. Used in t7xx_dpmaif_avail_pkt_bat_cnt().
> - Refactor t7xx_dpmaif_tx_send_skb() to protect tx_submit_skb_cnt
>   with spinlock and remove the misleading tx_drb_available variable.
> - Consolidate bit operations before endianness conversion.
> - Use C bit fields in dpmaif_drb_skb struct which is not HW related.
> - Add back the que_started check in t7xx_select_tx_queue().
> - Create a helper function to get the DRB count.
> - Simplify the use of 'usage' during t7xx_ccmni_close().
> - Enforce CCMNI MTU selection with BUILD_BUG_ON() instead of a comment.
> - Remove t7xx_ccmni_ctrl->capability parameter which remains constant.
>
> v4:
> - Implement list_prev_entry_circular() and list_next_entry_circular() macros.
> - Remove inline from all c files.
> - Define ioread32_poll_timeout_atomic() helper macro.
> - Fix return code for WWAN port tx op.
> - Allow AT commands fragmentation same as MBIM commands.
> - Introduce t7xx_common.h file in the first patch.
> - Rename functions and variables as suggested in v3.
> - Reduce code duplication by creating fsm_wait_for_event() helper function.
> - Remove unneeded dev_err in t7xx_fsm_clr_event().
> - Remove unused variable last_state from struct t7xx_fsm_ctl.
> - Remove unused variable txq_select_times from struct dpmaif_ctrl.
> - Replace ETXTBSY with EBUSY.
> - Refactor t7xx_dpmaif_rx_buf_alloc() to remove an unneeded allocation.
> - Fix potential leak at t7xx_dpmaif_rx_frag_alloc().
> - Simplify return value handling at t7xx_dpmaif_rx_start().
> - Add a helper to handle the common part of CCCI header initialization.
> - Make sure interrupts are enabled during PM resume.
> - Add a parameter to t7xx_fsm_append_cmd() to tell if it is in interrupt context.
>
> v3:
> - Avoid unneeded ping-pong changes between patches.
> - Use t7xx_ prefix in functions.
> - Use t7xx_ prefix in generic structs where mtk_ or ccci prefix was used.
> - Update Authors/Contributors header.
> - Remove skb pools used for control path.
> - Remove skb pools used for RX data path.
> - Do not use dedicated TX queue for ACK-only packets.
> - Remove __packed attribute from GPD structs.
> - Remove the infrastructure for test and debug ports.
> - Use the skb control buffer to store metadata.
> - Get the IP packet type from RX PIT.
> - Merge variable declaration and simple assignments.
> - Use preferred coding patterns.
> - Remove global variables.
> - Declare HW facing structure members as little endian.
> - Rename goto tags to describe what is going to be done.
> - Do not use variable length arrays.
> - Remove unneeded blank lines source code and kdoc headers.
> - Use C99 initialization format for port-proxy ports.
> - Clean up comments.
> - Review included headers.
> - Better use of 100 column limit.
> - Remove unneeded mb() in CLDMA.
> - Remove unneeded spin locks and atomics.
> - Handle read_poll_timeout error.
> - Use dev_err_ratelimited() where required.
> - Fix resource leak when requesting IRQs.
> - Use generic DEFAULT_TX_QUEUE_LEN instead custom macro.
> - Use ETH_DATA_LEN instead of defining WWAN_DEFAULT_MTU.
> - Use sizeof() instead of defines when the size of structures is required.
> - Remove unneeded code from netdev:
>     No need to configure HW address length
>     No need to implement .ndo_change_mtu
>     Remove random address generation
> - Code simplifications by using kernel provided functions and macros such as:
>     module_pci_driver
>     PTR_ERR_OR_ZERO
>     for_each_set_bit
>     pci_device_is_present
>     skb_queue_purge
>     list_prev_entry
>     __ffs64
>
> v2:
> - Replace pdev->driver->name with dev_driver_string(&pdev->dev).
> - Replace random_ether_addr() with eth_random_addr().
> - Update kernel-doc comment for enum data_policy.
> - Indicate the driver is 'Supported' instead of 'Maintained'.
> - Fix the Signed-of-by and Co-developed-by tags in the patches.
> - Added authors and contributors in the top comment of the src files.

Sorry for the delay in review. There are too many changes from version
to version and it took some time to dig through them. I would like to
admit that the driver now looks much better. Good job!

Please find per-patch comments.

--
Sergey

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