| Message ID | 20190314163725.7918-1-jbrunet@baylibre.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | pinctrl: meson: add g12a drive strength support | expand |
On Thu, 2019-03-14 at 17:37 +0100, Jerome Brunet wrote: > The purpose of this patchset is to add drive-strength support in meson pinconf > driver. This is a new feature that was added on the g12a. It is critical for us > to support this since many functions are failing with default pad drive-strength. > > Now the slightly annoying part :( > The value achievable by the SoC are 0.5mA, 2.5mA, 3mA and 4mA and the DT property > 'drive-strength' is expressed in mA. > > 1) Rounding down the value, we could be requesting a 0mA drive strength. > That would look weird. > 2) Rounding up, we can't distinguish between 2.5mA and 3mA > > To solve this issue in this in this v1, we chose to document that, on Amlogic, > drive-strength is expressed in uA instead of mA. > It works well and there is no impact on the other platforms but I'm not sure this > is really OK with the DT rules ? > > Linus, if this is not OK with you, here are 2 other options we are > considering. We would be very interested to get your opinion on the matter: > > 1) instead the generic 'drive-strength' property, we could add an amlogic > specific property, 'amlogic,drive-strength'. It would be expressed in uA > and parsed in amlogic specific code. > I think this option is kind of overkill. Expressing drive strength in uA is > not really amlogic specific so it does not make much sense, but it would > work ... > > 2) Add another generic property "drive-strength-uA". The change to do so > would be minimal and could be benefit to other platforms later on. Hi Linus, I know it has only been 10 days and you must be busy but I was wondering if we could get your view on the issue above ? Since the vast majority of SoC functions need a drive strength setting, DT patches are somehow blocked until we decide which binding to use for it. Sorry for this early ping. Jerome > > Cheers > Jerome > > Guillaume La Roque (2): > dt-bindings: pinctrl: meson: Add drive-strength property > pinctrl: meson: add support of drive-strength > > .../bindings/pinctrl/meson,pinctrl.txt | 3 + > drivers/pinctrl/meson/pinctrl-meson-g12a.c | 36 ++-- > drivers/pinctrl/meson/pinctrl-meson.c | 166 +++++++++++++----- > drivers/pinctrl/meson/pinctrl-meson.h | 20 ++- > 4 files changed, 165 insertions(+), 60 deletions(-) >
On Thu, Mar 14, 2019 at 11:37 PM Jerome Brunet <jbrunet@baylibre.com> wrote: > Now the slightly annoying part :( > The value achievable by the SoC are 0.5mA, 2.5mA, 3mA and 4mA and the DT property > 'drive-strength' is expressed in mA. > > 1) Rounding down the value, we could be requesting a 0mA drive strength. > That would look weird. > 2) Rounding up, we can't distinguish between 2.5mA and 3mA > > To solve this issue in this in this v1, we chose to document that, on Amlogic, > drive-strength is expressed in uA instead of mA. > It works well and there is no impact on the other platforms but I'm not sure this > is really OK with the DT rules ? I want the DT people to say what they think about this. > Linus, if this is not OK with you, here are 2 other options we are > considering. We would be very interested to get your opinion on the matter: > > 1) instead the generic 'drive-strength' property, we could add an amlogic > specific property, 'amlogic,drive-strength'. It would be expressed in uA > and parsed in amlogic specific code. > I think this option is kind of overkill. Expressing drive strength in uA is > not really amlogic specific so it does not make much sense, but it would > work ... > > 2) Add another generic property "drive-strength-uA". The change to do so > would be minimal and could be benefit to other platforms later on. I would go for 2). But we really need input from bindings people on this. Yours, Linus Walleij