Hello Nicolas,
On Thu, Jun 12, 2025 at 08:56:19PM +0200, Nicolas Frattaroli wrote:
>
> PCIE_CLIENT_RC_MODE/PCIE_CLIENT_EP_MODE was another field that wasn't
> super clear on what the bit field modification actually is. As far as I
> can tell, switching to RC mode doesn't actually write the correct value
> to the field if any of its bits have been set previously, as it only
> updates one bit of a 4 bit field.
>
> Replace it by actually writing the full values to the field, using the
> new HWORD_UPDATE macro, which grants us the benefit of better
> compile-time error checking.
The current code looks like this:
#define PCIE_CLIENT_RC_MODE HIWORD_UPDATE_BIT(0x40)
#define PCIE_CLIENT_EP_MODE HIWORD_UPDATE(0xf0, 0x0)
The device_type field is defined like this:
4'h0: PCI Express endpoint
4'h1: Legacy PCI Express endpoint
4'h4: Root port of PCI Express root complex
The reset value of the device_type field is 0x0 (EP mode).
So switching between RC mode / EP mode should be fine.
But I agree, theoretically there could be a bug if e.g. bootloader
has set the device_type to 0x1 (Legacy EP).
So if you want, you could send a patch:
-#define PCIE_CLIENT_RC_MODE HIWORD_UPDATE_BIT(0x40)
+#define PCIE_CLIENT_RC_MODE HIWORD_UPDATE(0xf0, 0x40)
With:
Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller
driver")
But I also think that your current patch is fine as-is.
I do however think that you can drop this line:
+#define PCIE_CLIENT_MODE_LEGACY 0x1U
Since the define is never used.
Also, is there any point in adding the U suffix?
Usually you see UL or ULL suffix, when that is needed, but there actually
seems to be extremely few hits of simply U suffix:
$ git grep 0x1U | grep -v UL
Kind regards,
Niklas
