linux-kernel - Re: [PATCH v3 2/2] at91: add Atmel ISI and ov2640 support on sam9m10/sam9g45 board.

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Date:	Fri, 30 Sep 2011 11:05:36 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Josh Wu <josh.wu@...el.com>
cc:	linux-media@...r.kernel.org, plagnioj@...osoft.com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	nicolas.ferre@...el.com, s.nawrocki@...sung.com
Subject: Re: [PATCH v3 2/2] at91: add Atmel ISI and ov2640 support on
 sam9m10/sam9g45 board.

On Thu, 22 Sep 2011, Josh Wu wrote:

> This patch
> 1. add ISI_MCK parent setting code when add ISI device.
> 2. add ov2640 support on board file.
> 3. define isi_mck clock in sam9g45 chip file.
> 
> Signed-off-by: Josh Wu <josh.wu@...el.com>

Looking a bit more at this, I think, the arch maintainer might want to 
take a closer look at this:

1. Wouldn't it be a good idea to also bind the isi_clk via a clock 
connection ID and not via the clock's name?

2. pck1 is not really dedicated to ISI on sam9g45. It can also be used, 
e.g., as a generic clock output and ISI_PCK can be supplied by an external 
oscillator. Such set up seems perfectly valid to me and your patch would 
just unconditionally grab PCK1 and configure it to some frequency... I 
think, this shall be improved.

3.

> +static int __init isi_set_clk_parent(void)
> +{
> +	struct clk *pck1;
> +	struct clk *plla;
> +	int ret;
> +
> +	/* ISI_MCK is supplied by PCK1 - set parent for it. */
> +	pck1 = clk_get(NULL, "pck1");
> +	if (IS_ERR(pck1)) {
> +		printk(KERN_ERR "Failed to get PCK1\n");
> +		ret = PTR_ERR(pck1);
> +		goto err;
> +	}
> +
> +	plla = clk_get(NULL, "plla");
> +	if (IS_ERR(plla)) {
> +		printk(KERN_ERR "Failed to get PLLA\n");
> +		ret = PTR_ERR(plla);
> +		goto err_pck1;
> +	}
> +	ret = clk_set_parent(pck1, plla);
> +	clk_put(plla);

I think, here you also need a

	clk_put(pck1);

> +	if (ret != 0) {
> +		printk(KERN_ERR "Failed to set PCK1 parent\n");
> +		goto err_pck1;
> +	}
> +	return ret;
> +
> +err_pck1:
> +	clk_put(pck1);
> +err:
> +	return ret;
> +}


Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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