linux-kernel - Re: [spi-devel-general] atmel

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: <200802181157.57299.david-b@pacbell.net>
Date:	Mon, 18 Feb 2008 11:57:56 -0800
From:	David Brownell <david-b@...bell.net>
To:	spi-devel-general@...ts.sourceforge.net
Cc:	Atsushi Nemoto <anemo@....ocn.ne.jp>, hskinnemoen@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [spi-devel-general] atmel_spi clock polarity

On Monday 18 February 2008, Atsushi Nemoto wrote:
> 	 IIRC the clock state follows
> CSRn.CPOL just before the real transfer.

No ... clock state should be valid *before* chipselect goes
active.  So I'm thinking the patch from Haavard is likely
the right change.


> Like this (previous transfer 
> was MODE 0, new transfer is MODE 3):
> 
>            T0                T1 T2
> 
> CS      ~~~|________________________________________________

So at T0, some chip is selected (and never deselected) ...

> 
> CLK     ______________________|~|___|~~~|___|~~~|___|~~~|___

... and at T1 CPOL is changed??  That's wrong.  There should
never be a partial clock period while a chipselect is active.
While it's inactive, sure -- no chip should care.


> 
> SO      ~~~~~~~~~~~~~~~~~~~~~~~~~~|___|~~~|___|~~~|___|~~~|_
>                                    MSB
> 
> T0-T1 was relatively longer then T1-T2.  I suppose T1 is not the
> point of updating MR register, but the point of starting DMA transfer.
> 
--
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/