linux-kernel - Re: [PATCH v3 6/8] serial: Add Tegra Combined UART driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180702134731.GI13096@ulmo>
Date:   Mon, 2 Jul 2018 15:47:31 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Mikko Perttunen <cyndis@...si.fi>
Cc:     Mikko Perttunen <mperttunen@...dia.com>,
        devicetree@...r.kernel.org, gregkh@...uxfoundation.org,
        jassisinghbrar@...il.com, linux-kernel@...r.kernel.org,
        jonathanh@...dia.com, linux-serial@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 6/8] serial: Add Tegra Combined UART driver

On Mon, Jul 02, 2018 at 04:30:07PM +0300, Mikko Perttunen wrote:
> On 02.07.2018 16:18, Thierry Reding wrote:
> > On Mon, Jul 02, 2018 at 02:40:31PM +0300, Mikko Perttunen wrote:
> > > The Tegra Combined UART (TCU) is a mailbox-based mechanism that allows
> > > multiplexing multiple "virtual UARTs" into a single hardware serial
> > > port. The TCU is the primary serial port on Tegra194 devices.
> > > 
> > > Add a TCU driver utilizing the mailbox framework, as the used mailboxes
> > > are part of Tegra HSP blocks that are already controlled by the Tegra
> > > HSP mailbox driver.
> > > 
> > > Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> > > ---
> > > 
> > > Notes:
> > >      v2:
> > >      - Removed (void) casts for unused variables.
> > >      - Changed the uart_set_options() call to be on one line, even if its
> > >        over 80 characters.
> > >      - Added defines for magic numbers.
> > >      - Style fixes.
> > >      - Changed Kconfig entry to depend on the Tegra HSP driver instead of
> > >        just the mailbox framework.
> > >      v3:
> > >      - Removed FLUSH bit, as it's unnecessary and slows down printing
> > >      - Removed call to uart_set_options
> > >      - Added mbox_free_channel calls to remove()
> > > 
> > >   drivers/tty/serial/Kconfig       |   9 ++
> > >   drivers/tty/serial/Makefile      |   1 +
> > >   drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
> > >   include/uapi/linux/serial_core.h |   3 +
> > >   4 files changed, 304 insertions(+)
> > >   create mode 100644 drivers/tty/serial/tegra-tcu.c
> > 
> > The driver looks good to me. But for my own understanding, is there some
> > way we can make use of the multiplexing? That is, could we add a
> > mechanism to have the driver filter out only a specific stream? Could we
> > also specify which stream to send data back to? What happens by default?
> > Which stream is data sent to?
> 
> There is no multiplexing on the producer/device side (i.e. what this driver
> does). The mailbox specified in device tree specifies the stream we send
> stuff to. The mailboxes are per-CPU (we use the CCPLEX mailbox here), so it
> cannot really be changed.

Oh, I see, so there is one stream per pair of mailboxes? That is, the
mailboxes we specify in the DT define which stream we receive from and
send to?

Thierry

Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)