Re: [PATCH V4 13/14] i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()

On Thu, Aug 06, 2026 at 04:18:56PM +0300, Adrian Hunter wrote:
> The MIPI I3C HCI driver needs to identify the underlying system device
> used for DMA mapping and PM operations. The logic for determining that
> device is currently embedded in the DMA implementation.
>
> Factor this code out into i3c_hci_sysdev() so it can be shared by other
> parts of the driver and keep the device-selection logic in one place.
>
> The explanatory comment moves with the code, reworked as kernel-doc now
> that it documents a function rather than an inline block.
>
> Signed-off-by: Adrian Hunter <[email protected]>
> ---

Reviewed-by: Frank Li <[email protected]>

>
>
> Changes in V4:
>
> 	Reworked the comment that moves with the code into kernel-doc,
> 	and mentioned that in the commit message.
>
> Changes in V2 and V3:
>
> 	None
>
>
>  drivers/i3c/master/mipi-i3c-hci/core.c | 16 ++++++++++++++++
>  drivers/i3c/master/mipi-i3c-hci/dma.c  | 15 +--------------
>  drivers/i3c/master/mipi-i3c-hci/hci.h  |  2 ++
>  3 files changed, 19 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index cfe9b5390b56..f95da427d7a9 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
> @@ -15,6 +15,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/iopoll.h>
>  #include <linux/module.h>
> +#include <linux/pci.h>
>  #include <linux/platform_data/mipi-i3c-hci.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> @@ -117,6 +118,21 @@ static inline struct i3c_hci *to_i3c_hci(struct i3c_master_controller *m)
>  	return container_of(m, struct i3c_hci, master);
>  }
>
> +/**
> + * i3c_hci_sysdev() - Get the device to use for DMA
> + * @dev: Device the HCI controller is bound to
> + *
> + * When an IOMMU is enabled, DMA API calls must use the device that IOMMU
> + * setup was done for.  Under PCI enumeration that is the PCI device, not
> + * the "mipi-i3c-hci" platform device below it.
> + *
> + * Return: @dev's parent if it is a PCI device, otherwise @dev.
> + */
> +struct device *i3c_hci_sysdev(struct device *dev)
> +{
> +	return dev->parent && dev_is_pci(dev->parent) ? dev->parent : dev;
> +}
> +
>  static void i3c_hci_set_master_dyn_addr(struct i3c_hci *hci)
>  {
>  	reg_write(MASTER_DEVICE_ADDR,
> diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
> index 0672ed1132f8..7c2b20474130 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/dma.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
> @@ -15,7 +15,6 @@
>  #include <linux/errno.h>
>  #include <linux/i3c/master.h>
>  #include <linux/io.h>
> -#include <linux/pci.h>
>
>  #include "hci.h"
>  #include "cmd.h"
> @@ -301,23 +300,11 @@ static int hci_dma_init(struct i3c_hci *hci)
>  {
>  	struct hci_rings_data *rings;
>  	struct hci_rh_data *rh;
> -	struct device *sysdev;
>  	u32 regval;
>  	unsigned int i, nr_rings, xfers_sz, resps_sz;
>  	unsigned int ibi_status_ring_sz, ibi_data_ring_sz;
>  	int ret;
>
> -	/*
> -	 * Set pointer to a physical device that does DMA and has IOMMU setup
> -	 * done for it in case of enabled IOMMU and use it with the DMA API.
> -	 * Here such device is either
> -	 * "mipi-i3c-hci" platform device (OF/ACPI enumeration) parent or
> -	 * grandparent (PCI enumeration).
> -	 */
> -	sysdev = hci->master.dev.parent;
> -	if (sysdev->parent && dev_is_pci(sysdev->parent))
> -		sysdev = sysdev->parent;
> -
>  	regval = rhs_reg_read(CONTROL);
>  	nr_rings = FIELD_GET(MAX_HEADER_COUNT_CAP, regval);
>  	dev_dbg(&hci->master.dev, "%d DMA rings available\n", nr_rings);
> @@ -332,7 +319,7 @@ static int hci_dma_init(struct i3c_hci *hci)
>  		return -ENOMEM;
>  	hci->io_data = rings;
>  	rings->total = nr_rings;
> -	rings->sysdev = sysdev;
> +	rings->sysdev = i3c_hci_sysdev(hci->master.dev.parent);
>
>  	for (i = 0; i < rings->total; i++) {
>  		u32 offset = rhs_reg_read(RHn_OFFSET(i));
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
> index b3d9803b1968..b8d2a3d680f8 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/hci.h
> +++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
> @@ -184,6 +184,8 @@ void amd_set_resp_buf_thld(struct i3c_hci *hci);
>  void i3c_hci_sync_irq_inactive(struct i3c_hci *hci);
>  int i3c_hci_process_xfer(struct i3c_hci *hci, struct hci_xfer *xfer, int n);
>
> +struct device *i3c_hci_sysdev(struct device *dev);
> +
>  #define DEFAULT_AUTOSUSPEND_DELAY_MS 1000
>
>  int i3c_hci_rpm_suspend(struct device *dev);
> --
> 2.53.0
>