linux-kernel - Re: [PATCH 2/3] k3dma: add support to reserved minimum channels

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Date:   Thu, 28 Jun 2018 11:32:39 +0530
From:   Vinod <vkoul@...nel.org>
To:     Guodong Xu <guodong.xu@...aro.org>
Cc:     robh+dt@...nel.org, mark.rutland@....com, dan.j.williams@...el.com,
        liyu65@...ilicon.com, suzhuangluan@...ilicon.com,
        xuhongtao8@...ilicon.com, zhongkaihua@...wei.com,
        xuezhiliang@...ilicon.com, xupeng7@...wei.com,
        sunliang10@...wei.com, fengbaopeng@...ilicon.com,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] k3dma: add support to reserved minimum channels

On 22-06-18, 11:24, Guodong Xu wrote:
> From: Li Yu <liyu65@...ilicon.com>
> 
> On k3 series of SoC, DMA controller reserves some channels for
> other on-chip coprocessors. By adding support to dma_min_chan, kernel
> will not be able to use these reserved channels.
> 
> One example is on Hi3660 platform, channel 0 is reserved to lpm3.
> 
> Please also refer to Documentation/devicetree/bindings/dma/k3dma.txt

and if some other platform has channel X marked for co-processor, maybe
a last channel or something in middle, how will this work then?

I am thinking this should be a mask, rather than min.

> 
> Signed-off-by: Li Yu <liyu65@...ilicon.com>
> Signed-off-by: Guodong Xu <guodong.xu@...aro.org>
> ---
>  drivers/dma/k3dma.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/k3dma.c b/drivers/dma/k3dma.c
> index fa31cccbe04f..13cec12742e3 100644
> --- a/drivers/dma/k3dma.c
> +++ b/drivers/dma/k3dma.c
> @@ -113,6 +113,7 @@ struct k3_dma_dev {
>  	struct dma_pool		*pool;
>  	u32			dma_channels;
>  	u32			dma_requests;
> +	u32			dma_min_chan;
>  	unsigned int		irq;
>  };
>  
> @@ -309,7 +310,7 @@ static void k3_dma_tasklet(unsigned long arg)
>  
>  	/* check new channel request in d->chan_pending */
>  	spin_lock_irq(&d->lock);
> -	for (pch = 0; pch < d->dma_channels; pch++) {
> +	for (pch = d->dma_min_chan; pch < d->dma_channels; pch++) {
>  		p = &d->phy[pch];
>  
>  		if (p->vchan == NULL && !list_empty(&d->chan_pending)) {
> @@ -326,7 +327,7 @@ static void k3_dma_tasklet(unsigned long arg)
>  	}
>  	spin_unlock_irq(&d->lock);
>  
> -	for (pch = 0; pch < d->dma_channels; pch++) {
> +	for (pch = d->dma_min_chan; pch < d->dma_channels; pch++) {
>  		if (pch_alloc & (1 << pch)) {
>  			p = &d->phy[pch];
>  			c = p->vchan;
> @@ -825,6 +826,8 @@ static int k3_dma_probe(struct platform_device *op)
>  				"dma-channels", &d->dma_channels);
>  		of_property_read_u32((&op->dev)->of_node,
>  				"dma-requests", &d->dma_requests);
> +		of_property_read_u32((&op->dev)->of_node,
> +				"dma-min-chan", &d->dma_min_chan);
>  	}
>  
>  	d->clk = devm_clk_get(&op->dev, NULL);
> @@ -848,12 +851,12 @@ static int k3_dma_probe(struct platform_device *op)
>  		return -ENOMEM;
>  
>  	/* init phy channel */
> -	d->phy = devm_kcalloc(&op->dev,
> -		d->dma_channels, sizeof(struct k3_dma_phy), GFP_KERNEL);
> +	d->phy = devm_kcalloc(&op->dev, (d->dma_channels - d->dma_min_chan),
> +			sizeof(struct k3_dma_phy), GFP_KERNEL);
>  	if (d->phy == NULL)
>  		return -ENOMEM;
>  
> -	for (i = 0; i < d->dma_channels; i++) {
> +	for (i = d->dma_min_chan; i < d->dma_channels; i++) {
>  		struct k3_dma_phy *p = &d->phy[i];
>  
>  		p->idx = i;
> -- 
> 2.17.1

-- 
~Vinod