linux-kernel - Re: [PATCH v5 1/5] dmaengine: imx-sdma: add clock ratio 1:1 check

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Date:   Mon, 28 Jan 2019 10:29:07 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     "Angus Ainslie (Purism)" <angus@...ea.ca>
Cc:     angus.ainslie@...i.sm, Vinod Koul <vkoul@...nel.org>,
        dmaengine@...r.kernel.org, NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Daniel Baluta <daniel.baluta@...il.com>
Subject: Re: [PATCH v5 1/5] dmaengine: imx-sdma: add clock ratio 1:1 check

Am Sonntag, den 27.01.2019, 23:08 -0700 schrieb Angus Ainslie (Purism):
> On i.mx8 mscale B0 chip, AHB/SDMA clock ratio 2:1 can't be supportted,
> since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
> to 500Mhz, so use 1:1 instead.
> 
> Based on NXP commit MLK-16841-1 by Robin Gong <yibin.gong@....com>
> 
> Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/dma/imx-sdma.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 0b3a67ff8e82..757fad2fbfae 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -440,6 +440,8 @@ struct sdma_engine {
>  	unsigned int			irq;
>  	dma_addr_t			bd0_phys;
>  	struct sdma_buffer_descriptor	*bd0;
> +	/* clock ratio for AHB:SDMA core. 1:1 is 1, 2:1 is 0*/
> +	bool				clk_ratio;
>  };
>  
>  static int sdma_config_write(struct dma_chan *chan,
> @@ -662,8 +664,11 @@ static int sdma_run_channel0(struct sdma_engine *sdma)
>  		dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
>  
>  	/* Set bits of CONFIG register with dynamic context switching */
> -	if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
> -		writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
> +	reg = readl(sdma->regs + SDMA_H_CONFIG);
> +	if ((reg & SDMA_H_CONFIG_CSM) == 0) {
> +		reg |= SDMA_H_CONFIG_CSM;
> +		writel_relaxed(reg, sdma->regs + SDMA_H_CONFIG);
> +	}
>  
>  	return ret;
>  }
> @@ -1840,6 +1845,9 @@ static int sdma_init(struct sdma_engine *sdma)
>  	if (ret)
>  		goto disable_clk_ipg;
>  
> +	if (clk_get_rate(sdma->clk_ahb) == clk_get_rate(sdma->clk_ipg))
> +		sdma->clk_ratio = 1;
> +
>  	/* Be sure SDMA has not started yet */
>  	writel_relaxed(0, sdma->regs + SDMA_H_C0PTR);
>  
> @@ -1880,8 +1888,10 @@ static int sdma_init(struct sdma_engine *sdma)
>  	writel_relaxed(0x4050, sdma->regs + SDMA_CHN0ADDR);
>  
>  	/* Set bits of CONFIG register but with static context switching */
> -	/* FIXME: Check whether to set ACR bit depending on clock ratios */
> -	writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
> +	if (sdma->clk_ratio)
> +		writel_relaxed(SDMA_H_CONFIG_ACR, sdma->regs + SDMA_H_CONFIG);
> +	else
> +		writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
>  
>  	writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);
>