Subject: Re: [PATCH 2/2] can: m_can: Add CAN clock generated by UPLLCK support

From: Marc Kleine-Budde <[email-masked]>
Date: Wed, 18 Nov 2015 11:23:06 +0100

On 11/18/2015 11:04 AM, Wenyou Yang wrote:
> As said SAMA5D2 datasheet, it is recommended to use the CAN clock
> at frequencies of 20, 40 or 80 MHz. To achieve these frequencies,
> PMC GCK3 must select the UPLLCK(480 MHz) as source clock and
> divide by 24, 12 or 6. In this patch the CAN clock at 20 MHz.
> 
> As it is configured through DT, it doesn't affect the M_CAN
> without configuring CAN clock and its generated clock.
> 
> Signed-off-by: Wenyou Yang <[email-masked]>

NACK

Please do this setup in your SoC code, where you setup the clock
infrastructure or have a look at
Documentation/devicetree/bindings/clock/clock-bindings.txt "Assigned
clock parents and rates"

> ---
> 
>  drivers/net/can/m_can/m_can.c |   16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index fd1caa0..2ca47db 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -269,6 +269,8 @@ enum m_can_mram_cfg {
>  #define TX_BUF_XTD		BIT(30)
>  #define TX_BUF_RTR		BIT(29)
>  
> +#define AT91_CAN_CLK_FREQ	20000000
> +
>  /* address offset and element number for each FIFO/Buffer in the Message RAM */
>  struct mram_cfg {
>  	u16 off;
> @@ -1188,7 +1190,7 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  	struct m_can_priv *priv;
>  	struct resource *res;
>  	void __iomem *addr;
> -	struct clk *hclk, *cclk;
> +	struct clk *hclk, *cclk, *upll_clk;
>  	int irq, ret;
>  
>  	hclk = devm_clk_get(&pdev->dev, "hclk");
> @@ -1198,6 +1200,18 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  		return -ENODEV;
>  	}
>  
> +	upll_clk = devm_clk_get(&pdev->dev, "upllclk");
> +	if (!IS_ERR(upll_clk)) {
> +		ret = clk_set_parent(cclk, upll_clk);
> +		if (!ret) {
> +			ret = clk_set_rate(cclk, AT91_CAN_CLK_FREQ);
> +			if (ret) {
> +				dev_err(&pdev->dev, "failed to set gck\n");
> +				return -ENODEV;
> +			}
> +		}
> +	}
> +
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "m_can");
>  	addr = devm_ioremap_resource(&pdev->dev, res);
>  	irq = platform_get_irq_byname(pdev, "int0");
> 

regards,
Marc

-- 
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