Re: [PATCH 2/3] nvme: Fix missing address translation for PCIe inbound access

[Torsten Duwe <duwe@lst.de>]

On Mon, 11 May 2026 16:50:48 +0200
Neil Armstrong <neil.armstrong@linaro.org> wrote:

> On 5/8/26 17:42, Torsten Duwe wrote:
[...]
> > +#define DEV_ADDR(a)		dev_phys_to_bus(dev->udev, (a))
> 
> This doesn't look very clean, I would do something closer to linux by precalculating
> the DMA addresses after allocation like:
> ====================><================================
> diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
> index 2b14437f69c..1ce06402a90 100644
> --- a/drivers/nvme/nvme.c
> +++ b/drivers/nvme/nvme.c
> @@ -241,6 +241,7 @@ static struct nvme_queue *nvme_alloc_queue(struct nvme_dev *dev,
>   	nvmeq->sq_cmds = (void *)memalign(4096, NVME_SQ_SIZE(depth));
>   	if (!nvmeq->sq_cmds)
>   		goto free_queue;
> +	nvmeq->sq_dma_addr = dev_phys_to_bus(dev->udev, nvmeq->sq_cmds);
>   	memset((void *)nvmeq->sq_cmds, 0, NVME_SQ_SIZE(depth));
> 
>   	nvmeq->dev = dev;
> @@ -393,7 +394,7 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
>   	dev->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
> 
>   	writel(aqa, &dev->bar->aqa);
> -	nvme_writeq((ulong)nvmeq->sq_cmds, &dev->bar->asq);
> +	nvme_writeq((ulong)nvmeq->sq_dma_addr, &dev->bar->asq);
>   	nvme_writeq((ulong)nvmeq->cqes, &dev->bar->acq);
> 
>   	result = nvme_enable_ctrl(dev);

Hm, time / space tradeoff. I don't really have a strong preference
regarding this, I'd worry most about U-Boot code size (for which this
doesn't make much of a difference). However, I was under the impression
that during regular NVMe business a lot of those buffers and addresses
get allocated and the translations are required often. That's probably
only true once a full-blown operating system is running.

I'll check the allocations and assignments. Any other opinions?

	Torsten