[U-Boot] [PATCH 1/2] usb: xhci: implement FEAT_POWER hook for switching regulators for ports
Dr. Philipp Tomsich
philipp.tomsich at theobroma-systems.com
Fri Nov 17 09:43:57 UTC 2017
Bin,
> On 17 Nov 2017, at 10:27, Bin Meng <bmeng.cn at gmail.com> wrote:
>
> Hi Philipp,
>
> On Tue, Nov 7, 2017 at 6:04 AM, Philipp Tomsich
> <philipp.tomsich at theobroma-systems.com <mailto:philipp.tomsich at theobroma-systems.com>> wrote:
>> When the FEAT_POWER flag is set/cleared for a port, power to this port
>> should be enabled/disabled. As many embedded xHCI controllers do not
>> expose a signal to control this, extra effort may be required.
>>
>> In order to link up setting/clearing FEAT_POWER with the regulator
>> framework (so either a regulator or a GPIO modelled as a fixed
>> regulator) can be switched, two callbacks are implemented in this
>> change: if regulators are available an optional property
>> 'xhci,port-power' can contain a stringlist with names of regulators
>> that should be switched to control the power of ports (each entry in
>> the stringlist corresponds to its respective regulator).
>>
>> For some versions of the RK3399-Q7 (at least revisions v1.1 and v1.2
>> are affected), we need to turn on the power for the port connected to
>> the on-module USB hub only when FEAT_POWER is set to ensure that the
>> hub does not enter a low-power mode that U-Boot's USB stack can't deal
>> with. Note that Linux eventually manages to attach the hub even when
>> it's in its low-power state after a few seconds.
>>
>
> Please help me understand the problem. At first glance, I don't think
> such change should be put in the xHCI core codes.
> To me, this patch sounds like we use the regulator to enable/disable
> the power to an external on-board USB hub. For the xHC root port, this
> port power on/off is already configured by the xHC registers.
The problem is that we have only a limited window of time between enabling
the power to the USB hub and the USB controller starting its link-up procedure
(i.e. reset of the port and waiting for a port-change), as the hub will otherwise
go into a low-power mode and only come up for a short period of time every
[I don’t remember the amount of time] milliseconds.
While this is no problem on Linux (the USB hub eventually gets detected after
a delay of 2-3 seconds), the U-Boot USB stack (as it’s not interrupt driven)
usually misses the port-change event (i.e. the probing has already moved on
by the time the USB hub tries again).
By having a callback directly from within the xHCI root-hub code, we can
ensure that we always catch the USB hub. We can’t fix this from the board
code, as the time between us enabling the regulator and the probing from
within ‘usb start’ will be unpredictable. My first instinct was to have a call
to a board-specific weak-function from xhci, but I finally settled on using
the regulator-framework to have some that can be reused in the general
case and also allows for on-demand power-on/off of on-board USB devices
(if anybody has the need for it).
>
>> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
>> ---
>>
>> drivers/usb/host/xhci.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 55 insertions(+)
>>
>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>> index 4673738..dabba18 100644
>> --- a/drivers/usb/host/xhci.c
>> +++ b/drivers/usb/host/xhci.c
>> @@ -30,6 +30,7 @@
>> #include <asm/unaligned.h>
>> #include <linux/errno.h>
>> #include "xhci.h"
>> +#include <power/regulator.h>
>>
>> #ifndef CONFIG_USB_MAX_CONTROLLER_COUNT
>> #define CONFIG_USB_MAX_CONTROLLER_COUNT 1
>> @@ -872,6 +873,58 @@ static u32 xhci_port_state_to_neutral(u32 state)
>> }
>>
>> /**
>> + * Switch power at an external regulator each port at the root hub, when
>> + * the FEAT_POWER feature is set/cleared.
>> + *
>> + * @param ctrl pointer to the xHCI controller
>> + * @param req_index port number as in the control message (one-based)
>> + * @param enable boolean indicating whether to enable or disable power
>> + * @return returns 0 on success, an error-code on failure
>> + */
>> +static int xhci_board_port_powerset(struct xhci_ctrl *ctrl, int req_index,
>> + bool enable)
>> +{
>> +#if CONFIG_IS_ENABLED(OF_CONTROL) && CONFIG_IS_ENABLED(DM_REGULATOR)
>> + /* We start counting ports at 0, while the request counts from 1. */
>> + int index = req_index - 1;
>> + struct udevice *dev = ctrl->dev;
>> + const char *regname = NULL;
>> + struct udevice *regulator;
>> + int ret;
>> +
>> + debug("%s: ctrl '%s' port %d enable %s\n", __func__,
>> + dev_read_name(dev), req_index, enable ? "true" : "false");
>> +
>> + ret = dev_read_string_index(dev, "xhci,port-power", index, ®name);
>> + if (ret < 0) {
>> + debug("%s: ctrl '%s' port %d: no entry in 'xhci,port-power'\n",
>> + __func__, dev_read_name(dev), req_index);
>> + return ret;
>> + }
>> +
>> + ret = regulator_get_by_platname(regname, ®ulator);
>> + if (ret) {
>> + debug("%s: ctrl '%s' port %d: could not get regulator '%s'\n",
>> + __func__, dev_read_name(dev), req_index, regname);
>> + return ret;
>> + }
>> +
>> + regulator_set_enable(regulator, enable);
>> +#endif
>> + return 0;
>> +}
>> +
>> +static int xhci_board_port_poweron(struct xhci_ctrl *ctrl, int req_index)
>> +{
>> + return xhci_board_port_powerset(ctrl, req_index, true);
>> +}
>> +
>> +static int xhci_board_port_poweroff(struct xhci_ctrl *ctrl, int req_index)
>> +{
>> + return xhci_board_port_powerset(ctrl, req_index, false);
>> +}
>> +
>> +/**
>> * Submits the Requests to the XHCI Host Controller
>> *
>> * @param udev pointer to the USB device structure
>> @@ -1036,6 +1089,7 @@ static int xhci_submit_root(struct usb_device *udev, unsigned long pipe,
>> xhci_writel(status_reg, reg);
>> break;
>> case USB_PORT_FEAT_POWER:
>> + xhci_board_port_poweron(ctrl, le16_to_cpu(req->index));
>> reg |= PORT_POWER;
>> xhci_writel(status_reg, reg);
>> break;
>> @@ -1056,6 +1110,7 @@ static int xhci_submit_root(struct usb_device *udev, unsigned long pipe,
>> reg &= ~PORT_PE;
>> break;
>> case USB_PORT_FEAT_POWER:
>> + xhci_board_port_poweroff(ctrl, le16_to_cpu(req->index));
>> reg &= ~PORT_POWER;
>> break;
>> case USB_PORT_FEAT_C_RESET:
>> --
>
> Regards,
> Bin
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