linux-kernel - Re: [PATCH v2 1/1] dmaengine: switchtec-dma: Introduce Switchtec DMA engine PCI driver

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Date:   Mon, 3 Apr 2023 22:26:28 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Kelvin Cao <kelvin.cao@...rochip.com>, vkoul@...nel.org,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     logang@...tatee.com, george.ge@...rochip.com
Subject: Re: [PATCH v2 1/1] dmaengine: switchtec-dma: Introduce Switchtec DMA
 engine PCI driver

Le 03/04/2023 à 20:06, Kelvin Cao a écrit :
> Some Switchtec Switches can expose DMA engines via extra PCI functions
> on the upstream ports. At most one such function can be supported on
> each upstream port. Each function can have one or more DMA channels.
> 
> Implement core PCI driver skeleton and register DMA engine callbacks.
> 
> Signed-off-by: Kelvin Cao <kelvin.cao@...rochip.com>
> Co-developed-by: George Ge <george.ge@...rochip.com>
> Signed-off-by: George Ge <george.ge@...rochip.com>
> ---
>   MAINTAINERS                 |    5 +
>   drivers/dma/Kconfig         |    9 +
>   drivers/dma/Makefile        |    1 +
>   drivers/dma/switchtec_dma.c | 1734 +++++++++++++++++++++++++++++++++++
>   4 files changed, 1749 insertions(+)
>   create mode 100644 drivers/dma/switchtec_dma.c
> 

Hi,
just a few nit, should you find them useful.

[...]

> +static void switchtec_dma_process_desc(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct device *chan_dev = to_chan_dev(swdma_chan);
> +	struct dmaengine_result res;
> +	struct switchtec_dma_desc *desc;
> +	struct switchtec_dma_hw_ce *ce;
> +	__le16 phase_tag;
> +	int tail;
> +	int cid;
> +	int se_idx;
> +	u32 sts_code;
> +	int i = 0;

No need to init.

[...]

> +static int switchtec_dma_alloc_desc(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
> +	struct pci_dev *pdev;
> +	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
> +	size_t size;
> +	struct switchtec_dma_desc *desc;
> +	int rc;
> +	int i;
> +
> +	swdma_chan->head = swdma_chan->tail = 0;
> +	swdma_chan->cq_tail = 0;
> +
> +	size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
> +	swdma_chan->hw_sq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
> +					       &swdma_chan->dma_addr_sq,
> +					       GFP_KERNEL);
> +	if (!swdma_chan->hw_sq) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	size = SWITCHTEC_DMA_CQ_SIZE * sizeof(*swdma_chan->hw_cq);
> +	swdma_chan->hw_cq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
> +					       &swdma_chan->dma_addr_cq,
> +					       GFP_KERNEL);
> +	if (!swdma_chan->hw_cq) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	memset(swdma_chan->hw_cq, 0, size);

The memory allocated with dma_alloc_coherent() is already zeroed.

> +
> +	/* reset host phase tag */
> +	swdma_chan->phase_tag = 0;
> +
> +	size = sizeof(*swdma_chan->desc_ring);
> +	swdma_chan->desc_ring = kcalloc(SWITCHTEC_DMA_RING_SIZE, size,
> +					GFP_KERNEL);
> +	if (!swdma_chan->desc_ring) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	memset(swdma_chan->desc_ring, 0, SWITCHTEC_DMA_RING_SIZE * size);

This is already kcalloc()'ed.

CJ