[PATCH v2 3/5] dmaengine: aspeed: Add AST2600 UART DMA driver

[Hillf Danton]

On 14 Mar 2023 10:18:15 +0800 Chia-Wei Wang <chiawei_wang at aspeedtech.com>
> +static irqreturn_t ast2600_udma_isr(int irq, void *arg)
> +{

[...]

> +	/* handle RX interrupt */
> +	sts = readl(udma->regs + UDMA_RX_INT_STS);
> +	for_each_set_bit(ch_bit, (unsigned long *)&sts, udma->n_ucs / 2) {
> +		ch_id = (ch_bit << 1) + 1;
> +		wptr = readl(udma->regs + UDMA_CH_WPTR(ch_id));
> +
> +		uc = &udma->ucs[ch_id];
> +		ud = &uc->ud;
> +		tx = &ud->tx;
> +
> +		uc->residue = (ud->size & ~UDMA_CH_CTRL_BUFSZ) - wptr;
> +
> +		/* handle non-4B-aligned case */
> +		if (ud->addr & 0x3) {
> +			p = phys_to_virt(dma_to_phys(uc->chan.device->dev, ud->addr));

This does not work if the dma address has no corresponding struct page.

> +			memcpy(p, uc->buf, wptr);
> +		}
> +
> +		ast2600_udma_terminate(&uc->chan);
> +
> +		dma_cookie_complete(tx);
> +		dma_descriptor_unmap(tx);
> +		dmaengine_desc_get_callback_invoke(tx, NULL);
> +	}
> +
> +	return IRQ_HANDLED;
> +}