linux-kernel - Re: [PATCH] serial: tegra: remove Kconfig dependency on APB DMA controller

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <aScp6mooEKUkBkA6@smile.fi.intel.com>
Date: Wed, 26 Nov 2025 18:25:14 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Francesco Lavra <flavra@...libre.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Kartik Rajput <kkartik@...dia.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Robert Marko <robert.marko@...tura.hr>,
	Thierry Bultel <thierry.bultel.yh@...renesas.com>,
	Douglas Anderson <dianders@...omium.org>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH] serial: tegra: remove Kconfig dependency on APB DMA
 controller

On Wed, Nov 26, 2025 at 01:08:23PM +0100, Francesco Lavra wrote:
> On Wed, 2025-11-26 at 13:20 +0200, Andy Shevchenko wrote:
> > On Wed, Nov 26, 2025 at 10:07:59AM +0100, Francesco Lavra wrote:

...

> > >         help
> > >           Support for the on-chip UARTs on the NVIDIA Tegra series SOCs
> > >           providing /dev/ttyTHS0, 1, 2, 3 and 4 (note, some machines
> > > may not
> > >           provide all of these ports, depending on how the serial port
> > > -         are enabled). This driver uses the APB DMA to achieve higher
> > > baudrate
> > > -         and better performance.
> > > +         are enabled).
> > 
> > I think this removes a good piece of information. Perhaps rephrase?
> > 
> >           This driver may use the APB DMA when available to achieve
> >           higher baudrate and better performance.
> 
> I think this sentence would make it sound like the driver performs better
> if the APB DMA controller is available, but in reality the driver just uses
> the generic DMA API like most serial drivers, and there is nothing APB-
> specific in it. If another DMA controller (e.g. GPC on Tegra234) is
> available instead of the APB one, the serial peripheral will be just as
> fast.

OK. But this is not the case for Tegra234? Or is it and it uses DMA for UART?

-- 
With Best Regards,
Andy Shevchenko