netdev - Re: [PATCH net-next v5 02/13] net: wwan: t7xx: Add control DMA interface

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Message-ID: <3867a1ee-9ff2-9afd-faf-ca5c31c0151d@linux.intel.com>
Date:   Fri, 25 Feb 2022 12:54:26 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Ricardo Martinez <ricardo.martinez@...ux.intel.com>
cc:     Netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org,
        kuba@...nel.org, davem@...emloft.net, johannes@...solutions.net,
        ryazanov.s.a@...il.com, loic.poulain@...aro.org,
        m.chetan.kumar@...el.com, chandrashekar.devegowda@...el.com,
        linuxwwan@...el.com, chiranjeevi.rapolu@...ux.intel.com,
        haijun.liu@...iatek.com, amir.hanania@...el.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        dinesh.sharma@...el.com, eliot.lee@...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 02/13] net: wwan: t7xx: Add control DMA
 interface

On Wed, 23 Feb 2022, Ricardo Martinez wrote:

> From: Haijun Liu <haijun.liu@...iatek.com>
> 
> Cross Layer DMA (CLDMA) Hardware interface (HIF) enables the control
> path of Host-Modem data transfers. CLDMA HIF layer provides a common
> interface to the Port Layer.
> 
> CLDMA manages 8 independent RX/TX physical channels with data flow
> control in HW queues. CLDMA uses ring buffers of General Packet
> Descriptors (GPD) for TX/RX. GPDs can represent multiple or single
> data buffers (DB).
> 
> CLDMA HIF initializes GPD rings, registers ISR handlers for CLDMA
> interrupts, and initializes CLDMA HW registers.
> 
> CLDMA TX flow:
> 1. Port Layer write
> 2. Get DB address
> 3. Configure GPD
> 4. Triggering processing via HW register write
> 
> CLDMA RX flow:
> 1. CLDMA HW sends a RX "done" to host
> 2. Driver starts thread to safely read GPD
> 3. DB is sent to Port layer
> 4. Create a new buffer for GPD ring
> 
> Signed-off-by: Haijun Liu <haijun.liu@...iatek.com>
> Signed-off-by: Chandrashekar Devegowda <chandrashekar.devegowda@...el.com>
> Co-developed-by: Ricardo Martinez <ricardo.martinez@...ux.intel.com>
> Signed-off-by: Ricardo Martinez <ricardo.martinez@...ux.intel.com>
> 
> >From a WWAN framework perspective:
> Reviewed-by: Loic Poulain <loic.poulain@...aro.org>
> ---

Since t7xx_pcie_mac_set_int and t7xx_pcie_mac_clear_int are
still not here, please note in your commit message there are
these dependencies between patches 02 and 03 (and I don't
promise somebody else wouldn't oppose).

> +{
...
> +	for (i = 0; i < ring->length; i++) {
...
> +		gpd = req->gpd;
...
> +	}
> +
> +	list_for_each_entry(req, &ring->gpd_ring, entry) {
> +		t7xx_cldma_rgpd_set_next_ptr(gpd, req->gpd_addr);
> +		gpd = req->gpd;

Despite being correct, this is bit of a trick. I'd add a comment
between the loops to help the reader to track where gpd points to.

> +/**
> + * t7xx_cldma_send_skb() - Send control data to modem.
> + * @md_ctrl: CLDMA context structure.
> + * @qno: Queue number.
> + * @skb: Socket buffer.
> + *
> + * Return:
...
> + * * -EBUSY	- Resource lock failure.

Leftover?


...with those addressed
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>


And kudos for rx_not_done -> pending_rx_int change. It was a minor
thing for me but the logic is so much easier to understand now with
that better name :-).

Some other nice cleanups compared with v4 also noted.


-- 
 i.