linux-kernel - Re: [PATCH v5 3/3] dmaengine: sf-pdma: Get number of channel by device tree

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Date:   Wed, 16 Feb 2022 14:52:14 +0800
From:   Zong Li <zong.li@...ive.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Bin Meng <bin.meng@...driver.com>,
        Green Wan <green.wan@...ive.com>,
        dmaengine <dmaengine@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v5 3/3] dmaengine: sf-pdma: Get number of channel by
 device tree

On Tue, Feb 15, 2022 at 8:06 PM Vinod Koul <vkoul@...nel.org> wrote:
>
> On 07-02-22, 14:30, Zong Li wrote:
> > It currently assumes that there are always four channels, it would
> > cause the error if there is actually less than four channels. Change
> > that by getting number of channel from device tree.
> >
> > For backwards-compatibility, it uses the default value (i.e. 4) when
> > there is no 'dma-channels' information in dts.
> >
> > Signed-off-by: Zong Li <zong.li@...ive.com>
> > ---
> >  drivers/dma/sf-pdma/sf-pdma.c | 21 ++++++++++++++-------
> >  drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
> >  2 files changed, 16 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> > index f12606aeff87..2ae10b61dfa1 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> >  static int sf_pdma_probe(struct platform_device *pdev)
> >  {
> >       struct sf_pdma *pdma;
> > -     struct sf_pdma_chan *chan;
> >       struct resource *res;
> > -     int len, chans;
> >       int ret;
> >       const enum dma_slave_buswidth widths =
> >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> >
> > -     chans = PDMA_NR_CH;
> > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> >       if (!pdma)
> >               return -ENOMEM;
> >
> > -     pdma->n_chans = chans;
> > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > +                                &pdma->n_chans);
> > +     if (ret) {
> > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
>
> This is useful for only debug i think, so dev_dbg perhaps
>

Thanks for your suggestion, let me change it in the next version.

> > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > +     }
> > +
> > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > +             return -EINVAL;
> > +     }
> >
> >       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >       pdma->membase = devm_ioremap_resource(&pdev->dev, res);
> > @@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
> >       struct sf_pdma_chan *ch;
> >       int i;
> >
> > -     for (i = 0; i < PDMA_NR_CH; i++) {
> > +     for (i = 0; i < pdma->n_chans; i++) {
> >               ch = &pdma->chans[i];
> >
> >               devm_free_irq(&pdev->dev, ch->txirq, ch);
> > @@ -574,6 +580,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
> >
> >  static const struct of_device_id sf_pdma_dt_ids[] = {
> >       { .compatible = "sifive,fu540-c000-pdma" },
> > +     { .compatible = "sifive,pdma0" },
> >       {},
> >  };
> >  MODULE_DEVICE_TABLE(of, sf_pdma_dt_ids);
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> > index 0c20167b097d..8127d792f639 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.h
> > +++ b/drivers/dma/sf-pdma/sf-pdma.h
> > @@ -22,11 +22,7 @@
> >  #include "../dmaengine.h"
> >  #include "../virt-dma.h"
> >
> > -#define PDMA_NR_CH                                   4
> > -
> > -#if (PDMA_NR_CH != 4)
> > -#error "Please define PDMA_NR_CH to 4"
> > -#endif
> > +#define PDMA_MAX_NR_CH                                       4
> >
> >  #define PDMA_BASE_ADDR                                       0x3000000
> >  #define PDMA_CHAN_OFFSET                             0x1000
> > @@ -118,7 +114,7 @@ struct sf_pdma {
> >       void __iomem            *membase;
> >       void __iomem            *mappedbase;
> >       u32                     n_chans;
> > -     struct sf_pdma_chan     chans[PDMA_NR_CH];
> > +     struct sf_pdma_chan     chans[PDMA_MAX_NR_CH];
>
> why waste memory allocating max, we know number of channels in probe,
> why not allocate runtime?
>

I kept it there because I'd like to do minimum change in this patch
set. You're right, let me change it in the next version.

> --
> ~Vinod