Messages in this thread | | | Subject | Re: [PATCH v4 2/2] Embedded USB Debugger (EUD) driver | From | Bryan O'Donoghue <> | Date | Tue, 4 Feb 2020 03:10:30 +0000 |
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On 03/02/2020 19:35, Bjorn Andersson wrote: > On Thu 30 Jan 20:43 PST 2020, Avaneesh Kumar Dwivedi wrote:
Hi Avaneesh.
> Please aim for keeping the sort order in this file (ignore QCOM_APR > which obviously is in the wrong place) > >> + tristate "QTI Embedded USB Debugger (EUD)" >> + depends on ARCH_QCOM
If we persist with the model of EXTCON you should "select EXTCON" here.
>> + help >> + The Embedded USB Debugger (EUD) driver is a driver for the >> + control peripheral which waits on events like USB attach/detach >> + and charger enable/disable. The control peripheral further helps >> + support the USB-based debug and trace capabilities. >> + This module enables support for Qualcomm Technologies, Inc. >> + Embedded USB Debugger (EUD).
Suggest.
This module enables support for Qualcomm Technologies, Inc. Embedded USB Debugger (EUD). The EUD is a control peripheral which reports VBUS attach/detach, charger enable/disable and USB-based debug and trace capabilities.
>> + * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
2020
>> + >> +static int enable_eud(struct eud_chip *priv) >> +{ >> + int ret; >> + >> + /* write into CSR to enable EUD */ >> + writel_relaxed(BIT(0), priv->eud_reg_base + EUD_REG_CSR_EUD_EN); >> + /* Enable vbus, chgr & safe mode warning interrupts */ >> + writel_relaxed(EUD_INT_VBUS | EUD_INT_CHGR | EUD_INT_SAFE_MODE, >> + priv->eud_reg_base + EUD_REG_INT1_EN_MASK); >> + >> + /* Ensure Register Writes Complete */
So... You are writing a register in an on-chip PMIC. The PMIC is responsible for detecting USB ID and supplying VBUS as appropriate.
You then get an interrupt to inform you of the state ?
>> +static ssize_t enable_store(struct device *dev, >> + struct device_attribute *attr, >> + const char *buf, size_t count) >> +{ >> + struct eud_chip *chip = dev_get_drvdata(dev); >> + int enable = 0; > > You shouldn't need to initialize this as you're checking the return > value of sscanf(). > >> + int ret = 0; >> + >> + if (sscanf(buf, "%du", &enable) != 1) >> + return -EINVAL; >> + >> + if (enable == EUD_ENABLE_CMD) >> + ret = enable_eud(chip); > > If ret is !0 you should probably return that, rather than count... > >> + else if (enable == EUD_DISABLE_CMD) >> + disable_eud(chip); >> + if (!ret) > > ...and then you don't need this check, or initialize ret to 0 above. > >> + chip->enable = enable; > > So if I write 42 to "enable" nothing will change in the hardware, but > chip->enable will be 42... > >> + return count; >> +}
I was just going to comment on usb_connector but, does the above code need a synchronization primitive to serialize with the worker and interrupt handler ?
>> +static int msm_eud_probe(struct platform_device *pdev) >> +{ >> + struct eud_chip *chip; >> + struct resource *res; >> + int ret; >> + >> + chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL); >> + if (!chip) >> + return -ENOMEM; >> + >> + chip->dev = &pdev->dev; >> + platform_set_drvdata(pdev, chip); >> + >> + chip->extcon = devm_extcon_dev_allocate(&pdev->dev, eud_extcon_cable); > > Aren't we moving away from extcon in favor of the usb role switching > thing?
Yes.
For the VBUS notification you could use
usb-role-switch and model the USB connector as a child-node of the dual-role controller.
See: https://patchwork.kernel.org/cover/11346247/ https://patchwork.kernel.org/patch/11346295/ https://patchwork.kernel.org/patch/11346263/
Avaneesh do you have any kernel code that cares about the charger state ?
What we are suggesting here is dropping extcon and using role-switching but, if you have some other code that cares about EXTCON_CHG_USB_SDP you'd have to do additional work.
But, if I understood the implication of the code above where you write to the PMIC and let it handle VBUS/CHARGER on/off and you are just notified of the state change, you should be fine with usb-role-switching.
--- bod
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