Re: [PATCH 1/2] spi: bcm2835: add spi-bcm2835aux driver for the auxiliar spi1 and spi2

On 22.07.2015, at 03:55, Stephen Warren [off-list ref] wrote:

However, I'd like to see a "semantic" driver for the shared register
region rather than a "syscon". IIUC, "syscon" simply provides a stylized
way for one driver to touch some shared registers directly without any
semantics. I'd strongly prefer to see a real driver inside Linux rather
than something that just lets drivers fiddle with the shared registers
willy nilly. Still, this aspect is an internal implementation detail
inside the kernel that we can change without external impact later if we
need.

More concerning: The bcm283x HW doesn't implement a "syscon" module, but
some semantic IP block. The DT should contain a real compatible value
that describes what the HW block really is, not just "syscon". We could
bind the syscon driver to this compatible value if we have to for

So, do I understand you correctly that if we would call the node 
bcm2835aux_enable as syscon with only the enable bit field register in it 
and add a enable_reg (pointing to the above) and enable_reg_mask=2 or 4
to the spi1/2 nodes then it would be acceptable? 

Would look like this:
spi2@7e2150c0 {
+    compatible = "brcm,bcm2835-aux-spi";
+    reg = <0x7e2150c0 0x40>;
+    interrupts = <1 29>;
+    clocks = <&clk_spi>;
+    #address-cells = <1>;
+    #size-cells = <0>;
+    cs-gpios = <&gpio 43>, <&gpio 44>, <&gpio 45>;
+    enable_reg = <&bcm2835aux_enable>;
+    enable_reg_mask = 4;
+};
+
+/* the necessary syscon config referenced above */
+bcm2835aux_enable: bcm2835aux_enable@0x7e215004 {
+    compatible = "syscon";
+    reg = <0x7e215004 0x04>;
+};


The uart aux driver would use:
+    enable_reg = <&bcm2835aux_enable>;
+    enable_reg_mask = 1;

Or maybe you would prefer a different naming?

The only use-case would be using:
regmap_update_bits(enable_reg, 0, enable_reg_mask, enable_reg_mask); /*enable */
regmap_update_bits(enable_reg, 0, enable_reg_mask, 0); /* disable */


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