Hey Andy, Linus,
Thanks for looking at this.
On 28/08/2020 11:09, Andy Shevchenko wrote:
On Fri, Aug 14, 2020 at 1:35 PM Thomas Preston
<thomas.preston@xxxxxxxxxxxxxxx> wrote:
- Fix a typo where mcp23x17 configs are referred to as mcp23x16.
I'm not sure it's correct. MPC23016 is an existing I²C IO expander.
The MCP23016 device is not mentioned anywhere else in this driver. The
only place this string is used is in `struct regmap_config
mcp23x17_regmap` (another device). It seems to me that this is a typo
but I might be wrong.
~/w/linux$ git grep -h compatible drivers/pinctrl/pinctrl-mcp23s08*
.compatible = "microchip,mcp23008",
.compatible = "microchip,mcp23017",
.compatible = "microchip,mcp23018",
.compatible = "mcp,mcp23008",
.compatible = "mcp,mcp23017",
.compatible = "microchip,mcp23s08",
.compatible = "microchip,mcp23s17",
.compatible = "microchip,mcp23s18",
.compatible = "mcp,mcp23s08",
.compatible = "mcp,mcp23s17",
Also I don't have an MC23016, so I can't test configuration for it.
- Fix precious range to include INTCAP{A,B}, which clear on read.
- Fix precious range to include GPIOB, which clears on read.
- Fix volatile range to include GPIOB, to fix debugfs registers
reporting different values than `gpioget gpiochip2 {0..15}`.
I'm wondering if you read all the datasheets before doing these changes.
MPC2308
MPC23016
MPC23017
...
I did not! I was only changing configuration for MCP23017 devices.
What have I missed?
For reference, I think you are referring to [0], [1], [2]. I'm familiar
with the last one.
-static const struct regmap_range mcp23x16_volatile_range = {
+static const struct regmap_range mcp23x17_volatile_range = {
.range_min = MCP_INTF << 1,
- .range_max = MCP_GPIO << 1,
+ .range_max = (MCP_GPIO << 1) + 1,
This looks weird. Usually we do a mask or a bit based mask, like (1 << x) - 1.
I don't think these are masks, they're addresses.
I believe the author has doubled the register indexing using a 1 bit
shift, because the MCP23017 device is configured with sequential
addresses (IOCON.BANK = 0). On page 12 of the datasheet [2] this looks like:
0x00 IODIRA, MCP_IODIR << 1
0x01 IODIRB
0x02 IPOLA, MCP_IPOL << 1
0x03 IPOLB
...
0x12 GPIOA, MCP_GPIO << 1
0x13 GPIOB
This means you can read 16 bits from MCP_GPIO << 1 and get the register
values for both banks, or even use this for .range_min.
However, this trick doesn't work for .range_max:
.range_max = MCP_GPIO << 1; /* 0x12 */
But I think it needs to be 0x13 to include GPIOB. Now that I'm looking
into it, how does `mcp23x17_regmap.val_bits = 16` affect this? Perhaps
`MCP_GPIO << 1` is fine after all.
I will whip up a v2 and test this. I'll split the changes across patches
and fix the typo last patch - in case you don't agree with me.
Many thanks,
Thomas
[0] MCP23008 https://ww1.microchip.com/downloads/en/DeviceDoc/21919e.pdf
[1] MCP23016 http://ww1.microchip.com/downloads/en/devicedoc/20090c.pdf
[2] MCP23017 https://ww1.microchip.com/downloads/en/DeviceDoc/20001952C.pdf
