linux-kernel - Re: [PATCH v3 3/4] dmaengine: dw-edma: Add support for native HDMA

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Date:   Mon, 13 Feb 2023 14:59:27 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Cai Huoqing <cai.huoqing@...ux.dev>
Cc:     Sergey.Semin@...kalelectronics.ru,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 3/4] dmaengine: dw-edma: Add support for native HDMA

On Mon, Feb 13, 2023 at 09:24:08PM +0800, Cai Huoqing wrote:
> From: Cai huoqing <cai.huoqing@...ux.dev>
> 
> Add support for HDMA NATIVE, as long the IP design has set
> the compatible register map parameter-HDMA_NATIVE,
> which allows compatibility for native HDMA register configuration.

Rewrap to fill 75 columns.  Also applies below.

> The HDMA Hyper-DMA IP is an enhancement of the eDMA embedded-DMA IP.
> And the native HDMA registers are different from eDMA,
> so this patch add support for HDMA NATIVE mode.
> 
> HDMA write and read channels operate independently to maximize
> the performance of the HDMA read and write data transfer over
> the link When you configure the HDMA with multiple read channels,
> then it uses a round robin (RR) arbitration scheme to select
> the next read channel to be serviced.
> The same applies when you have multiple write channels.

Wrap into a single paragraph or add a blank line if you want the last
sentence to be a new paragraph.

> The native HDMA driver also supports a maximum of 16 independent
> channels (8 write + 8 read), which can run simultaneously.
> Both SAR (Source Address Register) and DAR (Destination Address Register)
> are alignmented to byte.

s/alignmented/aligned/

> +	u32 watermark_en;			/* 0x0030 */
> +	u32	control1;			/* 0x0034 */
> +	u32	func_num;			/* 0x0038 */
> +	u32	qos;				/* 0x003c */
> +	u32	reserved;			/* 0x0040..0x007c */
> +	u32 ch_stat;				/* 0x0080 */

Weird indentation of control1, func_num, etc.  Is that meaningful or a
mistake?

> +	union {
> +		u64 reg;			/* 0x00a0..0x00a4 */
> +		struct {
> +			u32 lsb;		/* 0x00a0 */
> +			u32 msb;		/* 0x00a4 */
> +		};
> +	} msi_abort;
> +	u32	msi_msgdata;			/* 0x00a8 */

Again here.

Bjorn