linux-kernel - RE: [PATCH] serial: Add OMAP high-speed 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: <EAF47CD23C76F840A9E7FCE10091EFAB02C44C2348@dbde02.ent.ti.com>
Date:	Tue, 2 Mar 2010 20:43:24 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	"G, Manjunath Kondaiah" <manjugk@...com>,
	"S, Venkatraman" <svenkatr@...com>,
	Tony Lindgren <tony@...mide.com>,
	"Raja, Govindraj" <govindraj.raja@...com>,
	Greg KH <greg@...ah.com>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Olof Johansson <olof@...om.net>
Subject: RE: [PATCH] serial: Add OMAP high-speed UART driver.

> -----Original Message-----
> From: G, Manjunath Kondaiah
> Sent: Tuesday, March 02, 2010 8:34 PM
> To: Shilimkar, Santosh; S, Venkatraman; Tony Lindgren; Raja, Govindraj; Greg KH; linux-
> serial@...r.kernel.org; linux-omap@...r.kernel.org; linux-kernel@...r.kernel.org; Kevin Hilman; Olof
> Johansson
> Subject: RE: [PATCH] serial: Add OMAP high-speed UART driver.
> 
> 
> Santosh,
> 
> > -----Original Message-----
> > From: Shilimkar, Santosh
> > Sent: Tuesday, March 02, 2010 7:34 PM
> > To: G, Manjunath Kondaiah; S, Venkatraman; Tony Lindgren;
> > Raja, Govindraj; Greg KH; linux-serial@...r.kernel.org;
> > linux-omap@...r.kernel.org; linux-kernel@...r.kernel.org;
> > Kevin Hilman; Olof Johansson
> > Subject: RE: [PATCH] serial: Add OMAP high-speed UART driver.
> >
> > <snip snip>
> > > > > --
> > > > CDAC is a shadow register used for monitoring the DMA channel.
> > > >  I think it would be a lot
> > > > simpler if omap_start_dma() always resets CDAC to 0, and the
> > > > UART driver
> > > > just not set it explicitly.
> > >
> > > This seems to be better option than exposing CDAC read/write API
> > > to other drivers since user need to write '0' before
> > starting any DMA
> > > transfer which can be be done in omap_start_dma().
> > >
> > > I am wondering how other drivers are using DMA transfer
> > API's without
> > > resetting CDAC to zero.
> > >
> > It's needed only if some one is interested in that count.
> > UART seems to
> > using this counter where as other driver don't.
> >
> > Why do you think drivers need to know about counter value ?
> 
> Reading of non zero value(after reset to zero and enabling dma channel)
> from CDAC register indicates that, DMA transfer has started and user can
> rely on DMA4_CCENi and DMA4_CCFNi element and frame counters.
> 
> If the CDAC value is zero even after starting DMA channel, indicates
> error.
Not necessary. The DMA can still wait for the hw sync signal and the CDAC
can remain 0 if the hw sync in not received. This will be any way returned 
by DMA error ( SYNC lost)

This register was mainly suppose to be used for debug purposes.
Regards,
Santosh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/