Re: [v10,2/2] PCI: Rockchip: Add Rockchip PCIe controller support

Brian Norris
2016-09-01T17:14:01Z

On Thu, Sep 01, 2016 at 11:34:55AM -0500, Bjorn Helgaas wrote:
> In the interest of making progress, I made most of the changes Guenter
> suggested (thanks very much, Guenter!) and made some more of my own on
> top of those.

I'm not sure, but was this change your idea Bjorn?

commit 88cb3f59d73e261a3cd1957ff392f98c9916a5d1
Author: Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Date: Thu Sep 1 10:27:44 2016 -0500

Simplify the confusing HIWORD_UPDATE scheme.

[Which I'll summarize here; you're replacing the macro:

-/*
- * The higher 16-bit of this register is used for write protection
- * only if BIT(x + 16) set to 1 the BIT(x) can be written.
- */
-#define HIWORD_UPDATE(val, mask, shift) \
- ((val) << (shift) | (mask) << ((shift) + 16))

with its expansions:

+
+/*
+ * The higher 16-bit of this register is used for write protection
+ * only if BIT(x + 16) set to 1 the BIT(x) can be written.
+ */
+#define PCIE_CLIENT_CONF_ENABLE (0x00010000 | 0x0001)
+#define PCIE_CLIENT_LINK_TRAIN_ENABLE (0x00020000 | 0x0002)
+#define PCIE_CLIENT_ARI_ENABLE (0x00080000 | 0x0008)
+#define PCIE_CLIENT_CONF_LANE_NUM(x) (0x00300000 | (((x >> 1) & 3) << 4)
+#define PCIE_CLIENT_MODE_RC (0x00400000 | 0x0040)
+#define PCIE_CLIENT_GEN_SEL(x) (0x00800000 | ((x & 1) << 7)
+#define PCIE_CLIENT_GEN_SEL_0 0
+#define PCIE_CLIENT_GEN_SEL_2 1

Full change can be had by:
git fetch git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git pci/host-rockchip-wip
]

The use of HIWORD_UPDATE can indeed be a bit confusing, IMO, but this is
really a common Rockchip-ism that, once you read several of their
drivers, can make a little more sense. If you grep around, it's in at
least their clock, ethernet, SDHCI, PHY, and DP/DRM drivers. I might
defer to Heiko (upstream maintainer of Rockchip code) for a decision.
Maybe there's some intermediate ground where we keep the HIWORK_UPDATE()
logic (it does make sure we get the 16-bit shift right, I think) while
still refactoring a few other bits (like PCIE_CLIENT_CONF_LANE_NUM() and
PCIE_CLIENT_GEN_SEL() for wrapping HIWORK_UPDATE()?).

Anyway, just a thought. If it really is most understandable to write it
this way, then maybe it's fine to be different than the other 16
rockchip files that have this pattern.

Brian