Hi Josua,

On Mon, Oct 28, 2024 at 6:19 PM Josua Mayer [off-list ref] wrote:

Am 28.10.24 um 16:31 schrieb Vignesh Raghavendra:

quoted

On 25/10/24 19:27, Geert Uytterhoeven wrote:

quoted

On Mon, Feb 19, 2024 at 4:05 PM Josua Mayer [off-list ref] wrote:

quoted

HummingBoard-T features two M.2 connectors labeled "M1" and "M2".
The single SerDes lane of the SoC can be routed to either M1 pci-e
signals, or M2 usb-3 signals by a gpio-controlled mux.

Add overlays for each configuration.

Signed-off-by: Josua Mayer <redacted>

Thanks for your patch, which is now commit bbef42084cc170cb ("arm64:
dts: ti: hummingboard-t: add overlays for m.2 pci-e and usb-3") in v6.9.

quoted

--- /dev/null
+++ b/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dtso

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Josua Mayer <josua@solid-run.com>
+ *
+ * Overlay for SolidRun AM642 HummingBoard-T to enable USB-3.1.
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include <dt-bindings/phy/phy.h>
+
+#include "k3-serdes.h"
+
+&serdes0 {
+       #address-cells = <1>;
+       #size-cells = <0>;
+
+       serdes0_link: phy@0 {
+               reg = <0>;
+               cdns,num-lanes = <1>;
+               cdns,phy-type = <PHY_TYPE_USB3>;
+               #phy-cells = <0>;
+               resets = <&serdes_wiz0 1>;
+       };
+};
+
+&serdes_ln_ctrl {
+       idle-states = <AM64_SERDES0_LANE0_USB>;
+};
+
+&serdes_mux {
+       idle-state = <0>;
+};
+
+&usbss0 {
+       /delete-property/ ti,usb2-only;

/delete-property/ (and /delete-node/) to delete something in the base DTS
does not work.

My understanding is that flags are equivalent to boolean, i.e:

ti,usb2-only = <true>;
ti,usb2-only;

are equivalent.

If so, can we assign <false> within the overlay?

Unfortunately not. My first thought was "it depends on the actual code
in the driver", but that turns out to be wrong:

    static inline bool of_property_read_bool(const struct device_node *np,
                                             const char *propname)
    {
            const struct property *prop = of_find_property(np, propname, NULL);

            return prop ? true : false;
    }

    static inline bool of_property_present(const struct device_node
*np, const char *propname)
    {
            return of_property_read_bool(np, propname);
    }

So both methods just check if the property is present, and do not use
its value, when present (i.e. the former does not "read" the bool).

drivers/usb/cdns3/cdns3-ti.c uses device_property_read_bool:

    static inline bool device_property_read_bool(const struct device *dev,
                                                 const char *propname)
    {
            return device_property_present(dev, propname);
    }

so (at least for DT) that should map to the above.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds