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

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On Tue, 15 Feb 2022 22:52:14 PST (-0800), zong.li@xxxxxxxxxx wrote:
On Tue, Feb 15, 2022 at 8:06 PM Vinod Koul <vkoul@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
>  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.

Not sure if I'm missing something, but I don't see a v6. I'm going to assume that one will be sent, but the suggested changes look minor enough so
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

LMK if you guys were expecting this to go in via the RISC-V tree, otherwise I'll assume this aimed at the dmaengine tree. Probably best to keep
all three together, so feel free to take the DTS updates as well -- having some
shared tag never hurts, but the DTs don't move that much so any conflicts
should be straight-forward to just fix at merge time.

Thanks!

> +             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



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