On 13-12-18 03:56 PM, Sherman Yin wrote:
On 13-12-12 12:54 PM, Linus Walleij wrote:
+/*
+ * Write to the register using the value and mask if current value
is different
+ */
+static void capri_reg_write(struct pinctrl_dev *pctldev,
+ void __iomem *reg,
+ u32 val,
+ u32 mask)
+{
+ u32 old_val;
+ u32 new_val;
+
+ old_val = readl(reg);
+ new_val = (old_val & ~mask) | (val & mask);
+
+ if (new_val == old_val) {
+ dev_dbg(pctldev->dev,
+ "Reg 0x%p=0x%x (no change)\n",
+ reg, old_val);
+ return;
+ }
+
+ dev_dbg(pctldev->dev,
+ "Reg 0x%p change from 0x%x to 0x%x\n",
+ reg, old_val, new_val);
+ writel(new_val, reg);
+}
This is a reimplementation of regmap for MMIO.
See drivers/base/regmap/regmap-mmio.c
Notice how regmap_update_bits() is used throughout the
kernel.
If you want to do this, use regmap.
Ok.
As you can see in v4 of my patchset, I've changed my driver to use the
mmio regmap. However, as I was tracing through regmap_update_bits(), it
looks like I have to go through a lot of checks and function pointers
just to do a simple write to a register. Also, I have to select
REGMAP_MMIO which brings in a bunch of code as well.
I understand the benefits of using common code, but in this case it
seems there is a lot of extra code and run-time overhead to use regmap.
In the end it also doesn't buy much in terms of functionality.
Just a quick note - it looks like the 2nd parameter of
regmap_update_bits() wants the offset of a register (offset from
regmap_mmio_context.regs). So calling the parameter "reg" is a little
confusing, at least in the MMIO case.
Regards,
Sherman
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