linux-kernel - Re: [PATCH v3 6/7] USB: ohci-at91: add usb_clk for transition to common clk framework

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Date:	Tue, 16 Jul 2013 12:48:53 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Boris BREZILLON <b.brezillon@...rkiz.com>
cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3 6/7] USB: ohci-at91: add usb_clk for transition to
 common clk framework

On Tue, 16 Jul 2013, Boris BREZILLON wrote:

> The AT91 PMC (Power Management Controller) provides an USB clock used by
> USB Full Speed host (ohci) and USB Full Speed device (udc).
> The usb drivers (ohci and udc) must configure this clock to 48Mhz.
> This configuration was formely done in mach-at91/clock.c, but this
> implementation will be removed when moving to common clk framework.
> 
> This patch add support for usb clock retrieval and configuration, and is
> backward compatible with the current at91 clk implementation (if usb clk
> is not found, it does not configure/enable the usb clk).

But it does print a warning in the system log, right?

> @@ -144,6 +150,11 @@ static int usb_hcd_at91_probe(const struct hc_driver *driver,
>  		goto err2;
>  	}
>  
> +	uclk = clk_get(&pdev->dev, "usb_clk");
> +	if (IS_ERR(uclk)) {
> +		uclk = NULL;
> +		dev_warn(&pdev->dev, "failed to get usb_clk\n");
> +	}

Is this really what you want for backward compatibility?

Alan Stern

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