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

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Date:	Tue, 13 Nov 2012 15:37:16 +0800
From:	Mark Zhang <markz@...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 11/13/2012 02:41 PM, Thierry Reding wrote:
> * PGP Signed by an unknown key
> 
> On Tue, Nov 13, 2012 at 12:38:34PM +0800, Mark Zhang wrote:
>> On 11/12/2012 05:39 PM, Mark Zhang wrote:
>>> On 11/09/2012 09:20 PM, Thierry Reding wrote:
> [...]
>>>> @@ -1036,9 +1041,6 @@ static struct clk_duplicate tegra_clk_duplicates[] = {
>>>>         CLK_DUPLICATE("usbd",   "utmip-pad",    NULL),
>>>>         CLK_DUPLICATE("usbd",   "tegra-ehci.0", NULL),
>>>>         CLK_DUPLICATE("usbd",   "tegra-otg",    NULL),
>>>> -       CLK_DUPLICATE("hdmi",   "tegradc.0",    "hdmi"),
>>>> -       CLK_DUPLICATE("hdmi",   "tegradc.1",    "hdmi"),
>>>> -       CLK_DUPLICATE("host1x", "tegra_grhost", "host1x"),
>>>>         CLK_DUPLICATE("2d",     "tegra_grhost", "gr2d"),
>>>>         CLK_DUPLICATE("3d",     "tegra_grhost", "gr3d"),
>>>>         CLK_DUPLICATE("epp",    "tegra_grhost", "epp"),
>>>> @@ -1051,6 +1053,9 @@ static struct clk_duplicate tegra_clk_duplicates[] = {
>>>>         CLK_DUPLICATE("pll_p_out3", "tegra-i2c.1", "fast-clk"),
>>>>         CLK_DUPLICATE("pll_p_out3", "tegra-i2c.2", "fast-clk"),
>>>>         CLK_DUPLICATE("pll_p_out3", "tegra-i2c.3", "fast-clk"),
>>>> +       CLK_DUPLICATE("pll_p", "tegra-dc.0", "parent"),
>>>> +       CLK_DUPLICATE("pll_p", "tegra-dc.1", "parent"),
>>>> +       CLK_DUPLICATE("pll_d_out0", "tegra-hdmi", "parent"),
>>>>  };
>>
>> Why we need this "CLK_DUPLICATE"? Set the clock parent of the dc
>> controllers to pll_p?
> 
> This was the method proposed by Stephen to abstract away the clock tree
> differences between Tegra20 and Tegra30. The way this works is that we
> can {devm_,}clk_get(&pdev->dev, "parent") in the display and HDMI
> controllers' .probe() and it'll obtain the correct parent clock
> independent of which version of Tegra is used.
> 

Yes, after reading the corresponding codes in rgb.c & hdmi.c, I got how
this works. It's better than our previous version, I mean, the version
which we hard-code the clock parent setting logics in clock.c. But I
wanna say, it looks weird if you don't read the code of drm driver.

> Thierry
> 
> * Unknown Key
> * 0x7F3EB3A1
> 
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