On Mon, Mar 21, 2022 at 5:50 PM Sven Peter <sven@xxxxxxxxxxxxx> wrote:
> +static int apple_nvme_sart_dma_setup(void *cookie, struct apple_rtkit_shmem *bfr,
> + dma_addr_t iova, size_t size)
> +{
> + struct apple_nvme *anv = cookie;
> + int ret;
> +
> + if (iova)
> + return -EINVAL;
> +
> + bfr->buffer = dma_alloc_coherent(anv->dev, size, &iova, GFP_KERNEL);
> + if (!bfr->buffer)
> + return -ENOMEM;
You pass 'iova' as an argument, but then replace it with the address
returned by dma_alloc_coherent(). Can you remove the function
argument?
> +static void apple_nvmmu_inval(struct apple_nvme_queue *q, unsigned int tag)
> +{
> + struct apple_nvme *anv = queue_to_apple_nvme(q);
> +
> + writel(tag, anv->mmio_nvme + APPLE_NVMMU_TCB_INVAL);
> + if (readl_relaxed(anv->mmio_nvme + APPLE_NVMMU_TCB_STAT))
> + dev_warn(anv->dev, "NVMMU TCB invalidation failed\n");
> +}
I don't like to see the _relaxed() accessors used without an explanation
about why that helps. Please use the non-relaxed version, or make sure
it's obvious here why you use it.
> +bad_sgl:
> + WARN(DO_ONCE(apple_nvme_print_sgl, iod->sg, iod->nents),
> + "Invalid SGL for payload:%d nents:%d\n", blk_rq_payload_bytes(req),
> + iod->nents);
I think you mean WARN_ONCE() here?
> + writel_relaxed(0, anv->mmio_coproc + APPLE_ANS_COPROC_CPU_CONTROL);
> + (void)readl_relaxed(anv->mmio_coproc + APPLE_ANS_COPROC_CPU_CONTROL);
What is the purpose of the readl_relaxed() here? It looks like you are
trying to flush
the write to the hardware, but then again
a) on Apple hardware, the registers are mapped using PROT_DEVICE_nGnRnE,
so MMIO writes are never posted
b) the read is "_relaxed", so there is no barrier, and the result is
unused, so
it would appear that the CPU can just keep executing code anyway.
Since this is all the initialization path, I can't imagine what the
relaxation of
the barriers helps with.
> +static int apple_nvme_reg_read32(struct nvme_ctrl *ctrl, u32 off, u32 *val)
> +{
> + *val = readl_relaxed(ctrl_to_apple_nvme(ctrl)->mmio_nvme + off);
> + return 0;
> +}
> +
> +static int apple_nvme_reg_write32(struct nvme_ctrl *ctrl, u32 off, u32 val)
> +{
> + writel_relaxed(val, ctrl_to_apple_nvme(ctrl)->mmio_nvme + off);
> + return 0;
> +}
If you have generic register access functions, don't make them use
_relaxed internally. If there are instances that need to be _relaxed,
add another version of the accessor that spells this out in the caller.
Arnd
