On Mon, Mar 21, 2022 at 5:50 PM Sven Peter <sven@xxxxxxxxxxxxx> wrote:
>
> The NVMe co-processor on the Apple M1 uses a DMA address filter called
> SART for some DMA transactions. This adds a simple driver used to
> configure the memory regions from which DMA transactions are allowed.
>
> Co-developed-by: Hector Martin <marcan@xxxxxxxxx>
> Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
> Signed-off-by: Sven Peter <sven@xxxxxxxxxxxxx>
Can you add some explanation about why this uses a custom interface
instead of hooking into the dma_map_ops?
> +static void sart2_get_entry(struct apple_sart *sart, int index, u8 *flags,
> + phys_addr_t *paddr, size_t *size)
> +{
> + u32 cfg = readl_relaxed(sart->regs + APPLE_SART2_CONFIG(index));
> + u32 paddr_ = readl_relaxed(sart->regs + APPLE_SART2_PADDR(index));
Why do you use the _relaxed() accessors here and elsewhere in the driver?
> +struct apple_sart *apple_sart_get(struct device *dev)
> +{
> + struct device_node *sart_node;
> + struct platform_device *sart_pdev;
> + struct apple_sart *sart;
> +
> + sart_node = of_parse_phandle(dev->of_node, "apple,sart", 0);
> + if (!sart_node)
> + return ERR_PTR(ENODEV);
The error pointers need to take negative values, like 'ERR_PTR(-ENODEV)',
here and everywhere else in the driver.
Arnd
