Re: [PATCH V4 RESEND] dmaengine: Loongson1: Add Loongson1 dmaengine driver

[Kelvin Cheung <keguang.zhang@gmail.com>]

Vinod Koul <vkoul@kernel.org> 于2021年6月7日周一 下午7:07写道：
>
> On 21-05-21, 07:02, Keguang Zhang wrote:
>
> > +config LOONGSON1_DMA
> > +     tristate "Loongson1 DMA support"
> > +     depends on MACH_LOONGSON32
>
> Why does it have to do that? The dma driver is generic..

This driver is only available for LOONGSON32 CPUs.
>
> > +static int ls1x_dma_alloc_chan_resources(struct dma_chan *dchan)
> > +{
> > +     struct ls1x_dma_chan *chan = to_ls1x_dma_chan(dchan);
> > +
> > +     chan->desc_pool = dma_pool_create(dma_chan_name(dchan),
> > +                                       dchan->device->dev,
> > +                                       sizeof(struct ls1x_dma_lli),
> > +                                       __alignof__(struct ls1x_dma_lli), 0);
> > +     if (!chan->desc_pool) {
> > +             dev_err(chan2dev(dchan),
> > +                     "failed to alloc DMA descriptor pool!\n");
>
> This can be dropped, allocators will warn you for the allocation
> failures

will do.
>
> > +             return -ENOMEM;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static void ls1x_dma_free_desc(struct virt_dma_desc *vdesc)
> > +{
> > +     struct ls1x_dma_desc *desc = to_ls1x_dma_desc(vdesc);
> > +
> > +     if (desc->nr_descs) {
> > +             unsigned int i = desc->nr_descs;
> > +             struct ls1x_dma_hwdesc *hwdesc;
> > +
> > +             do {
> > +                     hwdesc = &desc->hwdesc[--i];
> > +                     dma_pool_free(desc->chan->desc_pool, hwdesc->lli,
> > +                                   hwdesc->phys);
> > +             } while (i);
> > +     }
> > +
> > +     kfree(desc);
> > +}
> > +
> > +static struct ls1x_dma_desc *ls1x_dma_alloc_desc(struct ls1x_dma_chan *chan,
> > +                                              int sg_len)
>
> single line now :)

will do.
>
> > +{
> > +     struct ls1x_dma_desc *desc;
> > +     struct dma_chan *dchan = &chan->vchan.chan;
> > +
> > +     desc = kzalloc(struct_size(desc, hwdesc, sg_len), GFP_NOWAIT);
> > +     if (!desc)
> > +             dev_err(chan2dev(dchan), "failed to alloc DMA descriptor!\n");
>
> this can be dropped too..

will do.
>
> > +static struct dma_async_tx_descriptor *
> > +ls1x_dma_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
> > +                    unsigned int sg_len,
> > +                    enum dma_transfer_direction direction,
> > +                    unsigned long flags, void *context)
> > +{
> > +     struct ls1x_dma_chan *chan = to_ls1x_dma_chan(dchan);
> > +     struct dma_slave_config *cfg = &chan->cfg;
> > +     struct ls1x_dma_desc *desc;
> > +     struct scatterlist *sg;
> > +     unsigned int dev_addr, bus_width, cmd, i;
> > +
> > +     if (!is_slave_direction(direction)) {
> > +             dev_err(chan2dev(dchan), "invalid DMA direction!\n");
> > +             return NULL;
> > +     }
> > +
> > +     dev_dbg(chan2dev(dchan), "sg_len=%d, dir=%s, flags=0x%lx\n", sg_len,
> > +             direction == DMA_MEM_TO_DEV ? "to device" : "from device",
> > +             flags);
> > +
> > +     switch (direction) {
> > +     case DMA_MEM_TO_DEV:
> > +             dev_addr = cfg->dst_addr;
> > +             bus_width = cfg->dst_addr_width;
> > +             cmd = LS1X_DMA_RAM2DEV | LS1X_DMA_INT;
> > +             break;
> > +     case DMA_DEV_TO_MEM:
> > +             dev_addr = cfg->src_addr;
> > +             bus_width = cfg->src_addr_width;
> > +             cmd = LS1X_DMA_INT;
> > +             break;
> > +     default:
> > +             dev_err(chan2dev(dchan),
> > +                     "unsupported DMA transfer mode! %d\n", direction);
> > +             return NULL;
>
> will this be ever executed?

just in case.
>
> > +static int ls1x_dma_slave_config(struct dma_chan *dchan,
> > +                              struct dma_slave_config *config)
> > +{
> > +     struct ls1x_dma_chan *chan = to_ls1x_dma_chan(dchan);
> > +
> > +     if (!dchan)
> > +             return -EINVAL;
>
> should this not be checked before you dereference this to get chan

will drop this check.
>
> > +static void ls1x_dma_trigger(struct ls1x_dma_chan *chan)
> > +{
> > +     struct dma_chan *dchan = &chan->vchan.chan;
> > +     struct ls1x_dma_desc *desc;
> > +     struct virt_dma_desc *vdesc;
> > +     unsigned int val;
> > +
> > +     vdesc = vchan_next_desc(&chan->vchan);
> > +     if (!vdesc) {
> > +             dev_warn(chan2dev(dchan), "No pending descriptor\n");
>
> Hmm, I would not log that... this is called from
> ls1x_dma_issue_pending() and which can be called from client driver but
> previous completion would push and this can find empty queue so it can
> happen quite frequently

will drop this warning.
>
> > +static irqreturn_t ls1x_dma_irq_handler(int irq, void *data)
> > +{
> > +     struct ls1x_dma_chan *chan = data;
> > +     struct dma_chan *dchan = &chan->vchan.chan;
> > +
> > +     dev_dbg(chan2dev(dchan), "DMA IRQ %d on channel %d\n", irq, chan->id);
> > +     if (!chan->desc) {
> > +             dev_warn(chan2dev(dchan),
> > +                      "DMA IRQ with no active descriptor on channel %d\n",
> > +                      chan->id);
>
> single line pls

will do.
>
> > +             return IRQ_NONE;
> > +     }
> > +
> > +     spin_lock(&chan->vchan.lock);
> > +
> > +     if (chan->desc->type == DMA_CYCLIC) {
> > +             vchan_cyclic_callback(&chan->desc->vdesc);
> > +     } else {
> > +             list_del(&chan->desc->vdesc.node);
> > +             vchan_cookie_complete(&chan->desc->vdesc);
> > +             chan->desc = NULL;
> > +     }
>
> not submitting next txn, defeats the purpose of dma if we dont push txns
> as fast as possible..

will fix it.
>
> > +static struct platform_driver ls1x_dma_driver = {
> > +     .probe  = ls1x_dma_probe,
> > +     .remove = ls1x_dma_remove,
> > +     .driver = {
> > +             .name   = "ls1x-dma",
> > +     },
>
> No device tree?

Because the LOONGSON32 platform doesn't support DT yet.
>
> --
> ~Vinod



-- 
Best regards,

Kelvin Cheung