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Date: Mon, 6 Dec 2021 18:41:03 -0800 From: "Martinez, Ricardo" <ricardo.martinez@...ux.intel.com> To: Sergey Ryazanov <ryazanov.s.a@...il.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@...iatek.com, amir.hanania@...el.com, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, dinesh.sharma@...el.com, eliot.lee@...el.com, mika.westerberg@...ux.intel.com, moises.veleta@...el.com, pierre-louis.bossart@...el.com, muralidharan.sethuraman@...el.com, Soumya.Prakash.Mishra@...el.com, sreehari.kancharla@...el.com, suresh.nagaraj@...el.com Subject: Re: [PATCH v2 06/14] net: wwan: t7xx: Add AT and MBIM WWAN ports On 12/1/2021 12:45 PM, Sergey Ryazanov wrote: > Hello Ricardo, > > On Wed, Dec 1, 2021 at 9:14 AM Martinez, Ricardo > <ricardo.martinez@...ux.intel.com> wrote: >> On 11/9/2021 4:06 AM, Sergey Ryazanov wrote: >>> On Mon, Nov 1, 2021 at 6:57 AM Ricardo Martinez wrote: >>>> ... >>>> static struct t7xx_port md_ccci_ports[] = { >>>> + {CCCI_UART2_TX, CCCI_UART2_RX, DATA_AT_CMD_Q, DATA_AT_CMD_Q, 0xff, >>>> + 0xff, ID_CLDMA1, PORT_F_RX_CHAR_NODE, &wwan_sub_port_ops, 0, "ttyC0", WWAN_PORT_AT}, >>>> + {CCCI_MBIM_TX, CCCI_MBIM_RX, 2, 2, 0, 0, ID_CLDMA1, >>>> + PORT_F_RX_CHAR_NODE, &wwan_sub_port_ops, 10, "ttyCMBIM0", WWAN_PORT_MBIM}, >>>> ... >>>> + if (count + CCCI_H_ELEN > txq_mtu && >>>> + (port_ccci->tx_ch == CCCI_MBIM_TX || >>>> + (port_ccci->tx_ch >= CCCI_DSS0_TX && port_ccci->tx_ch <= CCCI_DSS7_TX))) >>>> + multi_packet = DIV_ROUND_UP(count, txq_mtu - CCCI_H_ELEN); >>> I am just wondering, the chip does support MBIM message fragmentation, >>> but does not support AT commands stream (CCCI_UART2_TX) fragmentation. >>> Is that the correct conclusion from the code above? >> Yes, that is correct. > Are you sure that the modem does not support AT command fragmentation? > The AT commands interface is a stream of chars by its nature. It is > designed to work over serial lines. Some modem configuration software > even writes commands to a port in a char-by-char manner, i.e. it > writes no more than one char at a time to the port. > > The mechanism that is implemented in the driver to split user input > into individual messages is not a true fragmentation mechanism since > it does not preserve the original user input length. It just cuts the > user input into individual messages and sends them to the modem > independently. So, the modem firmware has no way to distinguish > whether the user input has been "fragmented" by the user or the > driver. How, then, does the modem firmware deal with an AT command > "fragmented" by a user? Will the modem firmware ignore the AT command > that is received in the char-by-char manner? The modem supports char-by-char AT command over serial lines, I'll get more information about why splitting long commands is supported only for MBIM and not for AT commands.
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