linux-kernel - Re: [PATCH] coresight: tmc: Configure DMA mask appropriately

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Date:   Fri, 19 May 2017 14:29:14 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Robin Murphy <robin.murphy@....com>, mathieu.poirier@...aro.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: tmc: Configure DMA mask appropriately

On 18/05/17 16:14, Robin Murphy wrote:
> Before making any DMA API calls, the ETR driver should really be setting
> its masks to ensure that DMA is possible. Especially since it can
> address more than the 32-bit default mask set by the AMBA bus code.
>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/hwtracing/coresight/coresight-tmc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
> index d8517d2a968c..864488793f09 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc.c
> @@ -362,6 +362,13 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  		desc.type = CORESIGHT_DEV_TYPE_SINK;
>  		desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
>  		desc.ops = &tmc_etr_cs_ops;
> +		/*
> +		 * ETR configuration uses a 40-bit AXI master in place of
> +		 * the embedded SRAM of ETB/ETF.
> +		 */
> +		ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(40));
> +		if (ret)
> +			goto out;
>  	} else {
>  		desc.type = CORESIGHT_DEV_TYPE_LINKSINK;
>  		desc.subtype.link_subtype = CORESIGHT_DEV_SUBTYPE_LINK_FIFO;
>

Tested this patch on Juno, with the SMMU enabled for the etr. I was able to
allocate 32M using (the CMA was only 16M). FWIW :

Tested-by: Suzuki K Poulose <suzuki.poulose@....com>