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From: Wolfgang Denk <wd@denx.de>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH] ppc4xx: Canyonlands: Fix USB host PHY reset sequence
Date: Mon, 14 Dec 2009 22:15:46 +0100	[thread overview]
Message-ID: <20091214211546.B8DD44C026@gemini.denx.de> (raw)
In-Reply-To: <AC5E1C3367E37D44970B81A6ADD1DA2C087E7893@SDCEXCHANGE01.ad.amcc.com>

Dear David,

In message <AC5E1C3367E37D44970B81A6ADD1DA2C087E7893@SDCEXCHANGE01.ad.amcc.com> you wrote:
>
> I generated several versions for a remote team to test (I don't have the
> failing hardware).
> Only the 100ms version worked every time.

I see :-(

> Actually we need the reset prior to Linux boot as well. Otherwise Linux
> will not discover attached devices. Which is the whole reason for the
> patch...

No, we don't. Why should we add a delay for all systems, even when
neither U-Boot not Linux will ever use any USB? For example ion
boards where not even a USB connector is physically present on the
hardware?

Please (re-) read the U-Boot Design Principles, item 2 "Keep it fast":
http://www.denx.de/wiki/view/U-Boot/DesignPrinciples#2_Keep_it_Fast

If USB is not used in U-Boot itself, U-Boot shall not  initialize  it
at all. And we should never impose restrictions or penalties (delays)
on everybody for features that are used only by some.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
In order to succeed in any enterprise, one  must  be  persistent  and
patient.  Even  if  one  has to run some risks, one must be brave and
strong enough to meet and overcome vexing challenges  to  maintain  a
successful  business  in  the  long  run.  I  cannot help saying that
Americans lack this necessary challenging spirit today.
- Hajime Karatsu

  reply	other threads:[~2009-12-14 21:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-12-14 20:09 [U-Boot] [PATCH] ppc4xx: Canyonlands: Fix USB host PHY reset sequence Dave Mitchell
2009-12-14 20:41 ` Wolfgang Denk
2009-12-14 20:48   ` David Mitchell
2009-12-14 21:15     ` Wolfgang Denk [this message]
2009-12-14 20:44 ` Wolfgang Denk

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