linux-kernel - Re: [PATCH v5 4/4] misc: fastrpc: Update dma

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Message-ID: <l6pf6zoz3sfawnsdmtacczykg2dgnaw4x26dfg4o3al44y7fc5@vgzd5s4uygm6>
Date: Sat, 6 Dec 2025 04:31:11 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Kumari Pallavi <kumari.pallavi@....qualcomm.com>
Cc: kpallavi@....qualcomm.com, srini@...nel.org, amahesh@....qualcomm.com,
        arnd@...db.de, gregkh@...uxfoundation.org, robh@...nel.org,
        krzk+dt@...nel.org, conor+dt@...nel.org, quic_bkumar@...cinc.com,
        ekansh.gupta@....qualcomm.com, linux-kernel@...r.kernel.org,
        quic_chennak@...cinc.com, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        jingyi.wang@....qualcomm.com, aiqun.yu@....qualcomm.com,
        ktadakam@....qualcomm.com
Subject: Re: [PATCH v5 4/4] misc: fastrpc: Update dma_bits for CDSP support
 on Kaanapali SoC

On Tue, Dec 02, 2025 at 11:36:28AM +0530, Kumari Pallavi wrote:
> DSP currently supports 32-bit IOVA (32-bit PA + 4-bit SID) for
> both Q6 and user DMA (uDMA) access. This is being upgraded to
> 34-bit PA + 4-bit SID due to a hardware revision in CDSP for
> Kaanapali SoC, which expands the DMA addressable range.
> Update DMA bits configuration in the driver to support CDSP on
> Kaanapali SoC. Set the default `dma_bits` to 32-bit and update
> it to 34-bit based on CDSP and OF matching on the fastrpc node.
> 
> Signed-off-by: Kumari Pallavi <kumari.pallavi@....qualcomm.com>
> ---
>  drivers/misc/fastrpc.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 6a67daafeaa1..c5d2c426fcbc 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -269,6 +269,8 @@ struct fastrpc_session_ctx {
>  
>  struct fastrpc_soc_data {
>  	u32 sid_pos;
> +	u32 dma_addr_bits_extended;

s/extended/cdsp/

> +	u32 dma_addr_bits_default;
>  };
>  
>  struct fastrpc_channel_ctx {
> @@ -2189,6 +2191,7 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  	int i, sessions = 0;
>  	unsigned long flags;
>  	int rc;
> +	u32 dma_bits;
>  
>  	cctx = dev_get_drvdata(dev->parent);
>  	if (!cctx)
> @@ -2202,12 +2205,16 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  		spin_unlock_irqrestore(&cctx->lock, flags);
>  		return -ENOSPC;
>  	}
> +	dma_bits = cctx->soc_data->dma_addr_bits_default;
>  	sess = &cctx->session[cctx->sesscount++];
>  	sess->used = false;
>  	sess->valid = true;
>  	sess->dev = dev;
>  	dev_set_drvdata(dev, sess);
>  
> +	if (cctx->domain_id == CDSP_DOMAIN_ID)
> +		dma_bits = cctx->soc_data->dma_addr_bits_extended;
> +
>  	if (of_property_read_u32(dev->of_node, "reg", &sess->sid))
>  		dev_info(dev, "FastRPC Session ID not specified in DT\n");
>  
> @@ -2222,9 +2229,9 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  		}
>  	}
>  	spin_unlock_irqrestore(&cctx->lock, flags);
> -	rc = dma_set_mask(dev, DMA_BIT_MASK(32));
> +	rc = dma_set_mask(dev, DMA_BIT_MASK(dma_bits));
>  	if (rc) {
> -		dev_err(dev, "32-bit DMA enable failed\n");
> +		dev_err(dev, "%u-bit DMA enable failed\n", dma_bits);
>  		return rc;
>  	}
>  
> @@ -2311,10 +2318,14 @@ static int fastrpc_get_domain_id(const char *domain)
>  
>  static const struct fastrpc_soc_data kaanapali_soc_data = {
>  	.sid_pos = 56,
> +	.dma_addr_bits_extended = 34,
> +	.dma_addr_bits_default = 32,
>  };
>  
>  static const struct fastrpc_soc_data default_soc_data = {
>  	.sid_pos = 32,
> +	.dma_addr_bits_extended = 32,
> +	.dma_addr_bits_default = 32,
>  };
>  
>  static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry