linux-kernel - Re: [PATCH 1/2] dmaengine: Introduce DW AXI DMAC driver

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Date:   Tue, 20 Feb 2018 15:39:17 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Cc:     dmaengine <dmaengine@...r.kernel.org>,
        linux-snps-arc@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Vinod Koul <vinod.koul@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@...el.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH 1/2] dmaengine: Introduce DW AXI DMAC driver

On Tue, Feb 20, 2018 at 2:30 PM, Eugeniy Paltsev
<Eugeniy.Paltsev@...opsys.com> wrote:
> This patch adds support for the DW AXI DMAC controller.
> DW AXI DMAC is a part of HSDK development board from Synopsys.
>
> In this driver implementation only DMA_MEMCPY transfers are
> supported.

Just few comments, code looks fine I hope.

> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13344,6 +13344,12 @@ F:     include/linux/dma/dw.h
>  F:     include/linux/platform_data/dma-dw.h
>  F:     drivers/dma/dw/
>
> +SYNOPSYS DESIGNWARE AXI DMAC DRIVER
> +M:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> +S:     Maintained
> +F:     drivers/dma/dwi-axi-dmac/
> +F:     Documentation/devicetree/bindings/dma/snps,dw-axi-dmac.txt

AXI is earlier in alphabet than DMAC in previous record.

Linus even submitted a script last year to sort the MAINTAINERS data base.

> +/*
> + * Synopsys DesignWare AXI DMA Controller driver.
> + *
> + * Copyright (C) 2017-2018 Synopsys, Inc. (www.synopsys.com)
> + * Author: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */

Now we have SPDX identifiers.

> +static u32 axi_chan_get_xfer_width(struct axi_dma_chan *chan, dma_addr_t src,
> +                                  dma_addr_t dst, size_t len)
> +{
> +       u32 max_width = chan->chip->dw->hdata->m_data_width;
> +
> +       return min_t(size_t, __ffs(src | dst | len), max_width);

size_t -> u32 ?

> +}

> +       unsigned int timeout = 20; /* timeout iterations */

> +       do  {
> +               if (axi_chan_irq_read(chan) & DWAXIDMAC_IRQ_SUSPENDED) {
> +                       ret = 0;
> +                       break;
> +               }
> +               udelay(2);
> +       } while (timeout--);

Off-by-one. You will have 21 tries here.

} while (--timeout);

-- 
With Best Regards,
Andy Shevchenko