[PATCH v2 2/8] pinctrl: stm32: Introduce HDP driver

[Clement LE GOFFIC]

On 5/21/25 11:49, Clement LE GOFFIC wrote:
> On 5/21/25 00:34, Linus Walleij wrote:
>> Hi Clément,
>>
>> thanks for your patch!
>>
>> On Tue, May 20, 2025 at 5:04 PM Clément Le Goffic
>> <clement.legoffic at foss.st.com> wrote:
>>
>>> This patch introduce the driver for the Hardware Debug Port available on
>>> STM32MP platforms. The HDP allows the observation of internal SoC
>>> signals by using multiplexers. Each HDP port can provide up to 16
>>> internal signals (one of them can be software controlled as a GPO).
>>>
>>> Signed-off-by: Clément Le Goffic <clement.legoffic at foss.st.com>
>>
>> (...)
>>> +static int stm32_hdp_gpio_get_direction(struct gpio_chip *gc, 
>>> unsigned int offset)
>>> +{
>>> +       return GPIO_LINE_DIRECTION_OUT;
>>> +}
>>
>> That's reasonable.
>>
>>> +static int stm32_hdp_gpio_get(struct gpio_chip *gc, unsigned int 
>>> offset)
>>> +{
>>> +       struct stm32_hdp *hdp = gpiochip_get_data(gc);
>>> +
>>> +       if (((hdp->mux_conf & HDP_MUX_MASK(offset))) == 
>>> HDP_MUX_GPOVAL(offset))
>>> +               return !!(readl_relaxed(hdp->base + HDP_GPOVAL) & 
>>> BIT(offset));
>>> +       else
>>> +               return !!(readl_relaxed(hdp->base + HDP_VAL) & 
>>> BIT(offset));
>>> +}
>>
>> ...but you still make it possible to read the value of the line
>> if it's not muxed as GPO?
>>
>> Should it not stm32_hdp_gpio_get_direction() return
>> GPIO_LINE_DIRECTION_IN if HDP_MUX_MASK(offset))) != 
>> HDP_MUX_GPOVAL(offset)?
> 
> Hi, oops, you're right !

I've answer too quickly. All the pins are "out" in fact.
The hardware is not able to read input signal.
I wanted to implement a way to read the register value in any case by 
leaving the line direction unchanged.

>>
>>> +static void stm32_hdp_gpio_set(struct gpio_chip *gc, unsigned int 
>>> offset, int value)
>>> +{
>>> +       struct stm32_hdp *hdp = gpiochip_get_data(gc);
>>> +
>>> +       if (value)
>>> +               writel_relaxed(BIT(offset), hdp->base + HDP_GPOSET);
>>> +       else
>>> +               writel_relaxed(BIT(offset), hdp->base + HDP_GPOCLR);
>>> +}
>>
>> Can't you just use GPIO_GENERIC for this?
>>
>> bgpio_init(gc, dev, ARRAY_SIZE(stm32_hdp_pins), // == 8
>>      hdp->base + HDP_VAL,
>>      hdp->base + HDP_GPOSET,
>>      hdp->base + HDP_GPOCLR,
>>      NULL,
>>      NULL,
>>      0);
>>
>> The default behaviour of GPIO MMIO is to read the output register
>> for the value if the line is in output mode.
>>
>> You may wanna override the .get_direction() callback after bgpio_init()
>> and before registering the chip, either with what you have or what
>> I described above.
> 
> I didn't know about it, I'll take a look and provide a V3.
> 
> Thank you,
> 
> Clément
> 
>> Yours,
>> Linus Walleij
>