linux-kernel - Re: [PATCH] ARM: tegra: apbio access using dma for tegra20 only

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Message-ID: <4FE0B061.6070302@wwwdotorg.org>
Date:	Tue, 19 Jun 2012 11:01:21 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	ccross@...roid.com, olof@...om.net, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: tegra: apbio access using dma for tegra20 only

On 06/19/2012 12:06 AM, Laxman Dewangan wrote:
> The Tegra20 HW issue with accessing APBIO registers (such
> as fuse registers) directly from the CPU concurrently with
> APB DMA accesses has been fixed in Tegra30 and later chips.
> 
> Access these registers directly from the CPU on Tegra30
> and later, and apply the workaround only for Tegra20.

> +void tegra_apb_io_init(void)
> +{
> +	/* Need to use dma only when it is Tegra20 based platform */
> +	if (of_machine_is_compatible("nvidia,tegra20")) {

That tests only works when the system is booted using device tree. Can
you change this to:

if (of_machine_is_compatible("nvidia,tegra20") ||
    !of_have_populated_dt()) {

... and make sure you get the expected result when booting using a board
file (e.g. Harmony). Thanks.

> +		apbio_read = tegra_apb_readl_using_dma;
> +		apbio_write = tegra_apb_writel_using_dma;
> +	} else {
> +		apbio_read = tegra_apb_readl_direct;
> +		apbio_write = tegra_apb_writel_direct;
> +	}
> +}
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