linux-kernel - Re: [PATCH v1] dmaengine: pl330: Make sure the debug is idle before doing DMAGO

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Date:   Wed, 24 Jun 2020 13:11:41 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Sugar Zhang <sugar.zhang@...k-chips.com>
Cc:     Dan Williams <dan.j.williams@...el.com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: pl330: Make sure the debug is idle before
 doing DMAGO

On 04-06-20, 09:36, Sugar Zhang wrote:
> According to the datasheet of pl330:
> 
> Example 2-1 Using DMAGO with the debug instruction registers
> 
> 1. Create a program for the DMA channel
> 2. Store the program in a region of system memory
> 3. Poll the DBGSTATUS Register to ensure that the debug is idle
> 4. Write to the DBGINST0 Register
> 5. Write to the DBGINST1 Register
> 6. Write zero to the DBGCMD Register
> 
> so, we should make sure the debug is idle before step 4/5/6, not
> only step 6. if not, there maybe a risk that fail to write DBGINST0/1.

Applied, thanks

> 
> Signed-off-by: Sugar Zhang <sugar.zhang@...k-chips.com>
> ---
> 
>  drivers/dma/pl330.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 88b884c..6a158ee 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -885,6 +885,12 @@ static inline void _execute_DBGINSN(struct pl330_thread *thrd,
>  	void __iomem *regs = thrd->dmac->base;
>  	u32 val;
>  
> +	/* If timed out due to halted state-machine */
> +	if (_until_dmac_idle(thrd)) {
> +		dev_err(thrd->dmac->ddma.dev, "DMAC halted!\n");
> +		return;
> +	}
> +
>  	val = (insn[0] << 16) | (insn[1] << 24);
>  	if (!as_manager) {
>  		val |= (1 << 0);
> @@ -895,12 +901,6 @@ static inline void _execute_DBGINSN(struct pl330_thread *thrd,
>  	val = le32_to_cpu(*((__le32 *)&insn[2]));
>  	writel(val, regs + DBGINST1);
>  
> -	/* If timed out due to halted state-machine */
> -	if (_until_dmac_idle(thrd)) {
> -		dev_err(thrd->dmac->ddma.dev, "DMAC halted!\n");
> -		return;
> -	}
> -
>  	/* Get going */
>  	writel(0, regs + DBGCMD);
>  }
> -- 
> 2.7.4
> 
> 

-- 
~Vinod