linux-kernel - Re: [RFC PATCH] dmaengine: sh: Correct src_addr_widths/dst_addr

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Date:   Thu, 12 Oct 2017 19:48:12 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Stefan Brüns <stefan.bruens@...h-aachen.de>
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Subject: Re: [RFC PATCH] dmaengine: sh: Correct
 src_addr_widths/dst_addr_widths bitmask setting

On Sun, Sep 17, 2017 at 04:45:39PM +0200, Stefan Brüns wrote:
> Obviously, the current value for the burst widths are wrong, and if this
> value is retrieved from some other subsystem using dma_get_slave_caps,
> it will wrongly assume burst width of e.g. 3 bytes are supported.
> 
> Each bit in the bitmask corresponds to a supported width, but it uses
> an encoding of BIT(<widths>), not BIT(log2<widths>), as it must be able
> to encode a width of 3 bytes.
> 
> The corollary is, it is not possible to encode either a width of 32 or
> 64 bytes, as the field has a size of 32 bits, and only a subset of the
> controller capabilities can be exposed.

well the right way would have been to fix this in the core by extending the
src/dst_addr_widths. I am sending a patch for that. please use that and
update this

> 
> Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
> ---
>  drivers/dma/sh/rcar-dmac.c | 14 ++++++++++----
>  drivers/dma/sh/shdmac.c    | 13 +++++++++----
>  drivers/dma/sh/usb-dmac.c  |  9 ++++++---
>  3 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 2b2c7db3e480..768076caccfd 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1734,10 +1734,16 @@ static int rcar_dmac_parse_of(struct device *dev, struct rcar_dmac *dmac)
>  
>  static int rcar_dmac_probe(struct platform_device *pdev)
>  {
> -	const enum dma_slave_buswidth widths = DMA_SLAVE_BUSWIDTH_1_BYTE |
> -		DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
> -		DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
> -		DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
> +	/*
> +	 * FIXME: Controller supports DMA_SLAVE_BUSWIDTH_32_BYTES
> +	 * and DMA_SLAVE_BUSWIDTH_64_BYTES,
> +	 * but this overflows the u32 src/dst_addr_widths fields
> +	 */
> +	const u32 widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)  |
> +			   BIT(DMA_SLAVE_BUSWIDTH_8_BYTES) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_16_BYTES);
>  	unsigned int channels_offset = 0;
>  	struct dma_device *engine;
>  	struct rcar_dmac *dmac;
> diff --git a/drivers/dma/sh/shdmac.c b/drivers/dma/sh/shdmac.c
> index c94ffab0d25c..bf35b5588b11 100644
> --- a/drivers/dma/sh/shdmac.c
> +++ b/drivers/dma/sh/shdmac.c
> @@ -679,10 +679,15 @@ MODULE_DEVICE_TABLE(of, sh_dmae_of_match);
>  
>  static int sh_dmae_probe(struct platform_device *pdev)
>  {
> -	const enum dma_slave_buswidth widths =
> -		DMA_SLAVE_BUSWIDTH_1_BYTE   | DMA_SLAVE_BUSWIDTH_2_BYTES |
> -		DMA_SLAVE_BUSWIDTH_4_BYTES  | DMA_SLAVE_BUSWIDTH_8_BYTES |
> -		DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES;
> +	/*
> +	 * FIXME: Controller supports DMA_SLAVE_BUSWIDTH_32_BYTES
> +	 * but this overflows the u32 src/dst_addr_widths fields
> +	 */
> +	const u32 widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)  |
> +			   BIT(DMA_SLAVE_BUSWIDTH_8_BYTES) |
> +			   BIT(DMA_SLAVE_BUSWIDTH_16_BYTES);
>  	const struct sh_dmae_pdata *pdata;
>  	unsigned long chan_flag[SH_DMAE_MAX_CHANNELS] = {};
>  	int chan_irq[SH_DMAE_MAX_CHANNELS];
> diff --git a/drivers/dma/sh/usb-dmac.c b/drivers/dma/sh/usb-dmac.c
> index 31a145154e9f..0ac7e842b70c 100644
> --- a/drivers/dma/sh/usb-dmac.c
> +++ b/drivers/dma/sh/usb-dmac.c
> @@ -768,7 +768,6 @@ static int usb_dmac_parse_of(struct device *dev, struct usb_dmac *dmac)
>  
>  static int usb_dmac_probe(struct platform_device *pdev)
>  {
> -	const enum dma_slave_buswidth widths = USB_DMAC_SLAVE_BUSWIDTH;
>  	struct dma_device *engine;
>  	struct usb_dmac *dmac;
>  	struct resource *mem;
> @@ -837,8 +836,12 @@ static int usb_dmac_probe(struct platform_device *pdev)
>  
>  	engine->dev = &pdev->dev;
>  
> -	engine->src_addr_widths = widths;
> -	engine->dst_addr_widths = widths;
> +	/*
> +	 * FIXME: The controller supports a width of USB_DMAC_SLAVE_BUSWIDTH,
> +	 * i.e. 32 bytes, but BIT(32) overflows the u32 bitmask fields.
> +	 */
> +	engine->src_addr_widths = 0;
> +	engine->dst_addr_widths = 0;
>  	engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
>  	engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
>  
> -- 
> 2.14.1
> 
> --
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-- 
~Vinod