Am Freitag, 2. September 2016, 10:44:09 schrieb Bjorn Helgaas:

On Thu, Sep 01, 2016 at 12:48:52PM -0500, Bjorn Helgaas wrote:

quoted

On Thu, Sep 01, 2016 at 10:14:01AM -0700, Brian Norris wrote:

quoted

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()?).

Here's a second proposal.  It retains HIWORD_UPDATE (though the structure
is different) so grep finds it along with the other Rockchip ones.

I'll post updated actual patches; this is just to give the idea:

-/*
-  * 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))

-#define PCIE_CLIENT_CONF_ENABLE			BIT(0)
-#define PCIE_CLIENT_CONF_ENABLE_SHIFT		0
-#define PCIE_CLIENT_CONF_ENABLE_MASK		0x1
-#define PCIE_CLIENT_LINK_TRAIN_ENABLE		1
-#define PCIE_CLIENT_LINK_TRAIN_SHIFT		1
-#define PCIE_CLIENT_LINK_TRAIN_MASK		0x1
-#define PCIE_CLIENT_ARI_ENABLE			BIT(0)
-#define PCIE_CLIENT_ARI_ENABLE_SHIFT		3
-#define PCIE_CLIENT_ARI_ENABLE_MASK		0x1
-#define PCIE_CLIENT_CONF_LANE_NUM(x)		(x / 2)
-#define PCIE_CLIENT_CONF_LANE_NUM_SHIFT		4
-#define PCIE_CLIENT_CONF_LANE_NUM_MASK		0x3
-#define PCIE_CLIENT_MODE_RC			BIT(0)
-#define PCIE_CLIENT_MODE_SHIFT			6
-#define PCIE_CLIENT_MODE_MASK			0x1
-#define PCIE_CLIENT_GEN_SEL_2			1
-#define PCIE_CLIENT_GEN_SEL_SHIFT		7
-#define PCIE_CLIENT_GEN_SEL_MASK		0x1

+/*
+ * The upper 16 bits of the PCIE_CLIENT registers are a write mask for the
+ * lower 16 bits.  This allows atomic updates of the register without
+ * locking.
+ */
+#define HIWORD_UPDATE(mask, val)	((mask << 16) | val)
+
+#define ENCODE_LANES(x)			(((x >> 1) & 3) << 4)
+
+#define PCIE_CLIENT_CONF_ENABLE		HIWORD_UPDATE(0x0001, 0x0001)
+#define PCIE_CLIENT_LINK_TRAIN_ENABLE	HIWORD_UPDATE(0x0002, 0x0002)
+#define PCIE_CLIENT_CONF_LANE_NUM(x)	HIWORD_UPDATE(0x0030, ENCODE_LANES(x))
+#define PCIE_CLIENT_GEN_SEL_2		HIWORD_UPDATE(0x0040, 0x0040)

 	rockchip_pcie_write(rockchip,
-		   HIWORD_UPDATE(PCIE_CLIENT_CONF_ENABLE,
-				 PCIE_CLIENT_CONF_ENABLE_MASK,
-				 PCIE_CLIENT_CONF_ENABLE_SHIFT) |
-		   HIWORD_UPDATE(PCIE_CLIENT_CONF_LANE_NUM(rockchip->lanes),
-				 PCIE_CLIENT_CONF_LANE_NUM_MASK,
-				 PCIE_CLIENT_CONF_LANE_NUM_SHIFT) |
-		   HIWORD_UPDATE(PCIE_CLIENT_MODE_RC,
-				 PCIE_CLIENT_MODE_MASK,
-				 PCIE_CLIENT_MODE_SHIFT) |
-		   HIWORD_UPDATE(PCIE_CLIENT_ARI_ENABLE,
-				 PCIE_CLIENT_ARI_ENABLE_MASK,
-				 PCIE_CLIENT_ARI_ENABLE_SHIFT) |
-		   HIWORD_UPDATE(PCIE_CLIENT_GEN_SEL_2,
-				 PCIE_CLIENT_GEN_SEL_MASK,
-				 PCIE_CLIENT_GEN_SEL_SHIFT),
-		   PCIE_CLIENT_BASE);
+			    PCIE_CLIENT_CONF_ENABLE |
+			    PCIE_CLIENT_LINK_TRAIN_ENABLE |
+			    PCIE_CLIENT_ARI_ENABLE |
+			    PCIE_CLIENT_CONF_LANE_NUM(rockchip->lanes) |
+			    PCIE_CLIENT_MODE_RC |
+			    PCIE_CLIENT_GEN_SEL_2,
+				PCIE_CLIENT_BASE);

I like this new approach :-)
Improves the readability in the code but also future readability of the defined 
constants, when comparing with register descriptions


Thanks
Heiko