Re: [PATCH v6 7/9] dmaengine: dw-edma: Add support for chip specific flags

From: Serge Semin <fancer.lancer@gmail.com>
To: Frank Li <Frank.Li@nxp.com>
Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>,
	gustavo.pimentel@synopsys.com, hongxing.zhu@nxp.com,
	l.stach@pengutronix.de, linux-imx@nxp.com,
	linux-pci@vger.kernel.org, dmaengine@vger.kernel.org,
	lznuaa@gmail.com, helgaas@kernel.org, vkoul@kernel.org,
	lorenzo.pieralisi@arm.com, robh@kernel.org, kw@linux.com,
	bhelgaas@google.com, manivannan.sadhasivam@linaro.org
Subject: Re: [PATCH v6 7/9] dmaengine: dw-edma: Add support for chip specific flags
Date: Wed, 13 Apr 2022 12:18:37 +0300	[thread overview]
Message-ID: <20220413091837.an75fiqazjhpapf4@mobilestation> (raw)
In-Reply-To: <20220406152347.85908-8-Frank.Li@nxp.com>

On Wed, Apr 06, 2022 at 10:23:45AM -0500, Frank Li wrote:
> Add a "flags" field to the "struct dw_edma_chip" so that the controller
> drivers can pass flags that are relevant to the platform.
> 
> DW_EDMA_CHIP_LOCAL - Used by the controller drivers accessing eDMA
> locally. Local eDMA access doesn't require generating MSIs to the remote.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---

> Change from v5 to v6
>  - use enum instead of define

Hm, why have you decided to do that? I don't see a well justified
reason to use the enumeration here, but see my next comment for
details.

> 
> Change from v4 to v5
>  - split two two patch
>  - rework commit message
> Change from v3 to v4
> none
> Change from v2 to v3
>  - rework commit message
>  - Change to DW_EDMA_CHIP_32BIT_DBI
>  - using DW_EDMA_CHIP_LOCAL control msi
>  - Apply Bjorn's comments,
>         if (!j) {
>                control |= DW_EDMA_V0_LIE;
>                if (!(chan->chip->flags & DW_EDMA_CHIP_LOCAL))
>                                control |= DW_EDMA_V0_RIE;
>         }
> 
>         if ((chan->chip->flags & DW_EDMA_CHIP_REG32BIT) ||
>               !IS_ENABLED(CONFIG_64BIT)) {
>           SET_CH_32(...);
>           SET_CH_32(...);
>        } else {
>           SET_CH_64(...);
>        }
> 
> 
> Change from v1 to v2
> - none
> 
>  drivers/dma/dw-edma/dw-edma-v0-core.c | 9 ++++++---
>  include/linux/dma/edma.h              | 9 +++++++++
>  2 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> index 8ddc537d11fd6..30f8bfe6e5712 100644
> --- a/drivers/dma/dw-edma/dw-edma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
> @@ -301,6 +301,7 @@ u32 dw_edma_v0_core_status_abort_int(struct dw_edma *dw, enum dw_edma_dir dir)
>  static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
>  {
>  	struct dw_edma_burst *child;
> +	struct dw_edma_chan *chan = chunk->chan;
>  	struct dw_edma_v0_lli __iomem *lli;
>  	struct dw_edma_v0_llp __iomem *llp;
>  	u32 control = 0, i = 0;
> @@ -314,9 +315,11 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
>  	j = chunk->bursts_alloc;
>  	list_for_each_entry(child, &chunk->burst->list, list) {
>  		j--;
> -		if (!j)
> -			control |= (DW_EDMA_V0_LIE | DW_EDMA_V0_RIE);
> -
> +		if (!j) {
> +			control |= DW_EDMA_V0_LIE;
> +			if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
> +				control |= DW_EDMA_V0_RIE;
> +		}
>  		/* Channel control */
>  		SET_LL_32(&lli[i].control, control);
>  		/* Transfer size */
> diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> index c2039246fc08c..bec444e2939b2 100644
> --- a/include/linux/dma/edma.h
> +++ b/include/linux/dma/edma.h
> @@ -33,6 +33,14 @@ enum dw_edma_map_format {
>  	EDMA_MF_HDMA_COMPAT = 0x5
>  };
>  

> +/**
> + * enum dw_edma_chip_flags - Flags specific to an eDMA chip
> + * @DW_EDMA_CHIP_LOCAL:		eDMA is used locally by an endpoint
> + */
> +enum dw_edma_chip_flags {
> +	DW_EDMA_CHIP_LOCAL	= BIT(0),
> +};
> +
>  /**
>   * struct dw_edma_chip - representation of DesignWare eDMA controller hardware
>   * @dev:		 struct device of the eDMA controller
> @@ -53,6 +61,7 @@ struct dw_edma_chip {
>  	int			id;
>  	int			nr_irqs;
>  	const struct dw_edma_core_ops   *ops;
> +	enum dw_edma_chip_flags	flags;

There is no point in having the named enumeration here since the flags
field semantics is actually a bitfield rather than a single value. If
you want to stick to the enumerated flags, then please use the
anonymous enum like this:
+enum {
+	DW_EDMA_CHIP_LOCAL	= BIT(0),
+};
and explicit unsigned int type of the flags field.

-Sergey

>  
>  	void __iomem		*reg_base;
>  
> -- 
> 2.35.1
> 