linux-kernel - Re: [PATCH 1/2] ARM: tegra: Add Tegra20 host1x support

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Date:	Wed, 14 Nov 2012 12:23:42 +0200
From:	Terje Bergström <tbergstrom@...dia.com>
To:	Thierry Reding <thierry.reding@...onic-design.de>
CC:	Stephen Warren <swarren@...dotorg.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] ARM: tegra: Add Tegra20 host1x support

On 14.11.2012 10:49, Thierry Reding wrote:
> Can you find out how the host1x clock is setup without this change? I
> was told that freezes can occur when you try to access the registers
> without the host1x clock being enabled. However, the host1x driver
> should take care to properly setup the clock.
> 
> To find out if the non-running clock is the issue, can you try to patch
> that line and make the final element true instead of false? That should
> enable the clock on boot so that it should always be running.

I tried with fastboot and U-Boot, and whenever that line is there,
kernel boot will halt at nvhost init. Same happens if I just change the
false to true.

nvhost will enable the clock and disable as it need. Also, part of
host1x initialization did proceed, but it ended up hanging after a few
registers were initialized. So it's not a case of host1x being off, but
host1x hanging after a while.

If I change this line to:

       { "host1x",     "pll_p",        216000000,      false },

it will also work properly. It looks like we have some problem with
pll_c in Tegra20, or clock configuration with your patch. In Tegra30,
pll_c with 144MHz seems to work fine, but on Tegra20, it doesn't.

In internal kernel, we use pll_c for host1x, so hardware shouldn't be
the problem here.

Best regards,
Terje
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