netdev - Re: [PATCH net-next 1/1] net: wwan: t7xx: Add AP CLDMA and GNSS port

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Date:   Fri, 17 Jun 2022 09:59:50 -0700
From:   "moises.veleta" <moises.veleta@...ux.intel.com>
To:     Loic Poulain <loic.poulain@...aro.org>
Cc:     netdev@...r.kernel.org, kuba@...nel.org, davem@...emloft.net,
        johannes@...solutions.net, ryazanov.s.a@...il.com,
        m.chetan.kumar@...el.com, chandrashekar.devegowda@...el.com,
        linuxwwan@...el.com, chiranjeevi.rapolu@...ux.intel.com,
        haijun.liu@...iatek.com, ricardo.martinez@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, dinesh.sharma@...el.com,
        ilpo.jarvinen@...ux.intel.com, moises.veleta@...el.com,
        Madhusmita Sahu <madhusmita.sahu@...el.com>
Subject: Re: [PATCH net-next 1/1] net: wwan: t7xx: Add AP CLDMA and GNSS port


On 6/16/22 10:29, Loic Poulain wrote:
> Hi Moises,
>
> On Tue, 14 Jun 2022 at 22:58, Moises Veleta
> <moises.veleta@...ux.intel.com> wrote:
>> From: Haijun Liu <haijun.liu@...iatek.com>
>>
>> The t7xx device contains two Cross Layer DMA (CLDMA) interfaces to
>> communicate with AP and Modem processors respectively. So far only
>> MD-CLDMA was being used, this patch enables AP-CLDMA and the GNSS
>> port which requires such channel.
>>
>> Signed-off-by: Haijun Liu <haijun.liu@...iatek.com>
>> Co-developed-by: Madhusmita Sahu <madhusmita.sahu@...el.com>
>> Signed-off-by: Madhusmita Sahu <madhusmita.sahu@...el.com>
>> Signed-off-by: Moises Veleta <moises.veleta@...ux.intel.com>
>> ---
> [...]
>>   static const struct t7xx_port_conf t7xx_md_port_conf[] = {
>>          {
>> +               .tx_ch = PORT_CH_AP_GNSS_TX,
>> +               .rx_ch = PORT_CH_AP_GNSS_RX,
>> +               .txq_index = Q_IDX_CTRL,
>> +               .rxq_index = Q_IDX_CTRL,
>> +               .path_id = CLDMA_ID_AP,
>> +               .ops = &wwan_sub_port_ops,
>> +               .name = "t7xx_ap_gnss",
>> +               .port_type = WWAN_PORT_AT,
> Is it really AT protocol here? wouldn't it be possible to expose it
> via the existing GNSS susbsystem?
>
> Regards,
> Looic

The protocol is AT.
It is not possible to using the GNSS subsystem as it is meant for 
stand-alone GNSS receivers without a control path. In this case, GNSS 
can used for different use cases, such as Assisted GNSS, Cell ID 
positioning, Geofence, etc. Hence, this requires the use of the AT 
channel on the WWAN subsystem.

Regards,
Moises