linux-kernel - Re: pinctrl: zynqmp: Valid pin muxings cannot be configured

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Date: Wed, 24 Apr 2024 08:22:33 +0200
From: Michal Simek <michal.simek@....com>
To: Sean Anderson <sean.anderson@...ux.dev>,
 "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Cc: Linus Walleij <linus.walleij@...aro.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: pinctrl: zynqmp: Valid pin muxings cannot be configured

Hi Sean,

On 4/24/24 01:04, Sean Anderson wrote:
> Hi Michal,
> 
> I was looking to upstream one of our ZynqMP boards, and I ran into an
> issue with the pinmuxing. We use almost all of the I/Os, so everything
> is tightly packed into the MIO. For example, we have the QSPI on MIO0 to
> MIO5, and MIO6 to MIO11 are used for SPI1. However, I cannot select this
> configuration using the pinmux driver. I am using the following
> configuration:
> 
> pinctrl_qspi_default: qspi-default {
> 	mux {
> 		groups = "qspi0_0_grp";
> 		function = "qspi0";
> 	};
> 
> 	mux-cs {
> 		groups = "qspi_ss_0_grp";
> 		function = "qspi_ss";
> 	};
> };
> 
> pinctrl_spi1_default: spi1-default {
> 	mux {
> 		groups = "spi1_0_grp";
> 		function = "spi1";
> 	};
> 
> 	mux-cs {
> 		groups = "spi1_ss_0_grp", "spi1_ss_1_grp";
> 		function = "spi1_ss";
> 	};
> };
> 
> But I get the following errors on boot:
> 
> [    4.261739] zynqmp-pinctrl firmware:zynqmp-firmware:pinctrl: pin MIO8 already requested by ff050000.spi; cannot claim for ff0f0000.spi
> [    4.274506] zynqmp-pinctrl firmware:zynqmp-firmware:pinctrl: error -EINVAL: pin-8 (ff0f0000.spi)
> [    4.283789] zynqmp-pinctrl firmware:zynqmp-firmware:pinctrl: error -EINVAL: could not request pin 8 (MIO8) from group qspi0_0_grp  on device zynqmp_pinctrl
> 
> This is because the qspi0_0_grp and spi1_0_grp groups overlap:
> 
> group: qspi0_0_grp
> pin 0 (MIO0)
> pin 1 (MIO1)
> pin 2 (MIO2)
> pin 3 (MIO3)
> pin 4 (MIO4)
> pin 8 (MIO8)
> pin 9 (MIO9)
> pin 10 (MIO10)
> pin 11 (MIO11)
> pin 12 (MIO12)
> 
> group: qspi_ss_0_grp
> pin 5 (MIO5)
> pin 7 (MIO7)
> 
> group: qspi_fbclk_0_grp
> pin 6 (MIO6)
> 
> group: spi1_0_grp
> pin 6 (MIO6)
> pin 10 (MIO10)
> pin 11 (MIO11)
> 
> group: spi1_ss_0_grp
> pin 9 (MIO9)
> 
> group: spi1_ss_1_grp
> pin 8 (MIO8)
> 
> group: spi1_ss_2_grp
> pin 7 (MIO7)
> 
> However, we are not using the "upper" pins of the QSPI device.
> Therefore, these pins should not be included in the qspi0_0_grp. This
> stems from the driver placing all possible pins into a function's group,
> even though each pin can be muxed individially and it is not necessary
> to mux all pins for full functionality.

Correct. These configurations were not consider at that time when code was 
written. The same issue is there if you want to combine pins from different 
groups. IIRC uart rx via MIOX and tx not from MIOX+1.

> 
> I think it would be better to have a single group for each pin:
> 
> pinctrl_qspi_default: qspi-default {
> 	mux {
> 		groups = "mio0", "mio1", "mio2", "mio3", "mio4";
> 		function = "qspi0";
> 	};
> 
> 	mux-cs {
> 		groups = "mio5";
> 		function = "qspi_ss";
> 	};
> };
> 
> pinctrl_spi1_default: spi1-default {
> 	mux {
> 		groups = "mio6", "mio10", "mio11";
> 		function = "spi1";
> 	};
> 
> 	mux-cs {
> 		groups = "mio8", "mio9";
> 		function = "spi1_ss";
> 	};
> };
> 
> This allows the full functionality of this chip to be configured. Does
> that sound good? I can send a patch to this effect if you agree.

The only question is if this can be done without changing TF-A code because we 
are running out of space in OCM for it.

Just a generic question to your problem. It doesn't sound like a dynamic case. 
You have static assignment for pins which likely won't change over lifecycle. 
QSPI can be even boot device. Do you really need to describe pins via DT that it 
is not enough to have them configured via psu_init directly?
Driver has been developed for i2c bus recovery via gpio which was the main 
application. Right now Kria SOM is using it for carrier card pins configuration.
And Kria is pretty much only platform where this is regularly tested.

Thanks,
Michal