linux-kernel - Re: [PATCH] stmmac: extend DMA initialization delay to 2.5 seconds

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Message-ID: <20140605143015.GD24240@lee--X1>
Date:	Thu, 5 Jun 2014 15:30:15 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Hans de Goede <hdegoede@...hat.com>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	srinivas.kandagatla@...aro.org, kernel@...inux.com
Subject: Re: [PATCH] stmmac: extend DMA initialization delay to 2.5 seconds

+Srinivas and the ST list.

> On some platforms existing 100 msecond delay is not enough for DMA block to
> recover after reset. This is because MAC DMA waits for all PHY input clocks
> to present and depending on the board reset bit deassertion may take much
> longer than previously used 100 milliseconds
> 
> I have a board that requires more than 2 seconds for DMA to zero "reset" bit.
> If for other boards it's still not long enough this value should be extended
> once again.
> 
> In the same change I convert "mdelay" to "msleep" to make CPU available for
> other processes during DMA init delay which is especially useful in case of
> delay for a few seconds.
> 
> Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> 
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>
> Cc: Chen-Yu Tsai <wens@...e.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: devicetree@...r.kernel.org
> Cc: Vineet Gupta <vgupta@...opsys.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c | 4 ++--
>  drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c  | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
> index 0c2058a..f713ea7 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
> @@ -39,11 +39,11 @@ static int dwmac1000_dma_init(void __iomem *ioaddr, int pbl, int fb, int mb,
>  	/* DMA SW reset */
>  	value |= DMA_BUS_MODE_SFT_RESET;
>  	writel(value, ioaddr + DMA_BUS_MODE);
> -	limit = 10;
> +	limit = 100;
>  	while (limit--) {
>  		if (!(readl(ioaddr + DMA_BUS_MODE) & DMA_BUS_MODE_SFT_RESET))
>  			break;
> -		mdelay(10);
> +		msleep(25);
>  	}
>  	if (limit < 0)
>  		return -EBUSY;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
> index 7d1dce9..043585f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
> @@ -41,11 +41,11 @@ static int dwmac100_dma_init(void __iomem *ioaddr, int pbl, int fb, int mb,
>  	/* DMA SW reset */
>  	value |= DMA_BUS_MODE_SFT_RESET;
>  	writel(value, ioaddr + DMA_BUS_MODE);
> -	limit = 10;
> +	limit = 100;
>  	while (limit--) {
>  		if (!(readl(ioaddr + DMA_BUS_MODE) & DMA_BUS_MODE_SFT_RESET))
>  			break;
> -		mdelay(10);
> +		msleep(25);
>  	}
>  	if (limit < 0)
>  		return -EBUSY;

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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