On Tue, Oct 3, 2023 at 6:42 PM Dipen Patel <dipenp@xxxxxxxxxx> wrote: > > On 10/3/23 1:58 AM, Bartosz Golaszewski wrote: > > On Mon, Oct 2, 2023 at 6:27 PM Dipen Patel <dipenp@xxxxxxxxxx> wrote: > >> > >> On 10/2/23 1:33 AM, Bartosz Golaszewski wrote: > >>> On Fri, Sep 29, 2023 at 11:38 PM Dipen Patel <dipenp@xxxxxxxxxx> wrote: > >>>> > >>>> On 9/11/23 2:44 AM, Bartosz Golaszewski wrote: > >>>>> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > >>>>> > >>>>> Using any of the GPIO interfaces using the global numberspace is > >>>>> deprecated. Make it clear in the comment. > >>>>> > >>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > >>>>> Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > >>>>> --- > >>>>> This was part of a wider series but since this is independent, I'm sending > >>>>> it separately. > >>>>> > >>>>> drivers/hte/hte-tegra194.c | 13 ++++++++----- > >>>>> 1 file changed, 8 insertions(+), 5 deletions(-) > >>>>> > >>>>> diff --git a/drivers/hte/hte-tegra194.c b/drivers/hte/hte-tegra194.c > >>>>> index 6fe6897047ac..9fd3c00ff695 100644 > >>>>> --- a/drivers/hte/hte-tegra194.c > >>>>> +++ b/drivers/hte/hte-tegra194.c > >>>>> @@ -407,12 +407,15 @@ static int tegra_hte_line_xlate(struct hte_chip *gc, > >>>>> return -EINVAL; > >>>>> > >>>>> /* > >>>>> + * GPIO consumers can access GPIOs in two ways: > >>>>> * > >>>>> - * There are two paths GPIO consumers can take as follows: > >>>>> - * 1) The consumer (gpiolib-cdev for example) which uses GPIO global > >>>>> - * number which gets assigned run time. > >>>>> - * 2) The consumer passing GPIO from the DT which is assigned > >>>>> - * statically for example by using TEGRA194_AON_GPIO gpio DT binding. > >>>>> + * 1) Using the global GPIO numberspace. > >>>>> + * > >>>>> + * This is the old, now DEPRECATED method and should not be used in > >>>>> + * new code. TODO: Check if tegra is even concerned by this. > >>>> This use case is to do namespace mapping from gpio subsystem to hte. Few doubts: > >>>> 1. What does deprecate mean here? Does gpio subsys not use global space anymore? > >>> > >>> It does but we don't want to expose this to external users in any way > >>> anymore (and haven't to for years). This is what deprecated means. > >>> Users should deal with opaque GPIO descriptors not global GPIO > >>> numberspace. > >>> > >>>> 2. If yes, what GPIO number is set when it comes from gpiolib-cdev, as based on that I may have to > >>>> reflect in the mapping, tegra194_aon_gpio_map for example. > >>> > >>> Why DO you have to use a GPIO number though? If HTE needs just a > >>> number from some HTE numberspace (which in itself may be unnecessary) > >>> then why not just keep a local IDA for it? Do you have to know the > >>> GPIOs internal numbering scheme to make it work? > >> > > > > Dipen, > > > > Please set your mailer to wrap lines around at 80 characters as is > > customary on the mailing list. > > my email client misfired, will make sure. Thanks. > > > >> humm, overall, I just need to know which GPIO it is, for example, GPIO controller X Port A GPIO number 3 > >> to do proper mapping. > >> Continuing from above example, the hte driver gets: > >> - GPIO Controller X from DT node > >> - the rest details in current code gets it from [1] and [2] > >> > >> If there is alternate method exists, I would like to explore. I think IDA will not help in this case as ID assigned > >> does not hold meaning in this context. > >> > >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpio/gpiolib-cdev.c?h=v6.6-rc3#n760 > > > > Here: any reason why we have to translate the desc to the global GPIO > > numberspace? Can we just pass the descriptor pointer directly to the > > HTE subsystem? > Sure, if from GPIO descriptor with combination of any helper APIs from > the GPIO subsystem can help identify the GPIO pin, we can eliminate the need > to pass global number (I assume gpio desc > can be only accessed/manipulated using GPIO subsystem APIs) > > > > >> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/hte/hte-tegra194.c?h=v6.6-rc3#n421 > > > > I still don't understand why you need to know the GPIO base? I'm not > > quite sure what the role of line_id is in this driver. Is it only to > > index the array? > > > > Please bear with me, I don't know this subsystem very well. > > Sure, no problem. Let me see if I am able to elaborate: > > 1. Map arrays' indexes are GPIO offsets so to avoid having > the extra field for the GPIO numbers. > > 2. The HTE driver needs to know exact GPIO to enable corresponding bits > in its registers. For example, hte register bit 3 would correspond to > GPIO 6 of GPIO controller X. If gpio descriptor is passed here, I think > I would need to do some conversions to identify the GPIO to enable > corresponding register bits. In the current scheme of things, > I though it was easier to identify passing the output of the desc_to_gpio* API. > > 3. Since GPIO global space is runtime, need base to calculate the offset > where offset does not change. So in the above example, gpio cdev would pass > 306 and HTE does simple conversion from the base, ie. 306 - 300 = 6. > Now 6 will serve as pin number as map array index to find the register. > > 4. Overall, I rely on base + global number to do namespace conversion > between gpio and hte subsys as far as gpio-cdev use case is concerned. > Ok, so you *don't* need the global numbers, just controller-relative offsets. This makes sense. This ties nicely into my plan for removing all accesses to gpio_chip except for GPIO providers. Looking at the tegra dts I'm surprised that the GPIO controllers that use the HTE don't take the hte_lic or hte_aon phandles as arguments. How exactly do they resolve the HTE device to use for timestamping? In any case, I think this commit is still correct. Bart > > > > Bart > > > >> > >>> > >>> Bart > >>> > >>>>> + * > >>>>> + * 2) Using GPIO descriptors that can be assigned to consumer devices > >>>>> + * using device-tree, ACPI or lookup tables. > >>>>> * > >>>>> * The code below addresses both the consumer use cases and maps into > >>>>> * HTE/GTE namespace. > >>>> > >> >
