Messages in this thread | | | Subject | Re: [PATCH 1/3] pinctrl: mcp23s08: Fixup mcp23x17 regmap_config | From | Thomas Preston <> | Date | Fri, 28 Aug 2020 20:19:54 +0100 |
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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@codethink.co.uk> 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
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