| Message ID | 20230126-gpio-mmio-fix-v1-1-8a20ce0e8275@ncr.com |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | Introduce new optional property to mark port as write only | expand |
| Context | Check | Description |
|---|---|---|
| robh/checkpatch | success | |
| robh/patch-applied | success |
On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: > From: Niall Leonard <nl250060@ncr.com> Subject: missing "wd,mbl-gpio:" prefix. Subject: drop second/last, redundant "bindings". The "dt-bindings" prefix is already stating that these are bindings. > > Added optional "no-input" property Missing full stop. > > Signed-off-by: Niall Leonard <nl250060@ncr.com> > --- > Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > index 038c3a6a1f4d..9405f9dad522 100644 > --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > @@ -18,6 +18,7 @@ Required properties: > > Optional properties: > - no-output: GPIOs are read-only. > + - no-input: GPIOs are write-only. Read is via a shadow register. Why this property is needed? Why driver cannot always use shadow register? Anyway, please convert the bindings to DT schema first (see writing-schema and example-schema). Documentation/devicetree/bindings/writing-schema.rst Best regards, Krzysztof
> -----Original Message----- > From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> > Sent: 26 January 2023 12:29 > To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij > <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob > Herring <robh+dt@kernel.org>; Krzysztof Kozlowski > <krzysztof.kozlowski+dt@linaro.org> > Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- > kernel@vger.kernel.org > Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio > bindings > > *External Message* - Use caution before opening links or attachments > > On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: > > From: Niall Leonard <nl250060@ncr.com> > > Subject: missing "wd,mbl-gpio:" prefix. > > Subject: drop second/last, redundant "bindings". The "dt-bindings" > prefix is already stating that these are bindings. > > > > > Added optional "no-input" property > > Missing full stop. > > > > > Signed-off-by: Niall Leonard <nl250060@ncr.com> > > --- > > Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > > b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > > index 038c3a6a1f4d..9405f9dad522 100644 > > --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > > +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > > @@ -18,6 +18,7 @@ Required properties: > > > > Optional properties: > > - no-output: GPIOs are read-only. > > + - no-input: GPIOs are write-only. Read is via a shadow register. > > Why this property is needed? Why driver cannot always use shadow > register? > The shadow register is currently only used during the write operation. It is not available during the read operation. That is essentially the change I have submitted. An alternative approach would have been to develop an entire new gpio driver similar to the 74xx driver, but I felt this approach was better. > Anyway, please convert the bindings to DT schema first (see writing-schema > and example-schema). > Documentation/devicetree/bindings/writing-schema.rst > The bindings for this driver are duplicated in a few files even though they use the same driver. i.e. wd,mbl-gpio.txt, ni,169445-nand-gpio.txt, brcm,bcm6345-gpio.yaml I don't know why these multiple bindings exist. It would perhaps make sense to remove these duplicate binding documentation files and replace with a single one for "basic-mmio-gpio". I happened to pick ". wd,mbl-gpio.txt", but I could have just as easily chosen one of the other 2. What's your view ? > Best regards, > Krzysztof
Hi Niall, thanks for your patch! On Thu, Jan 26, 2023 at 11:18 AM Niall Leonard via B4 Submission Endpoint <devnull+nl250060.ncr.com@kernel.org> wrote: > Optional properties: > - no-output: GPIOs are read-only. > + - no-input: GPIOs are write-only. Read is via a shadow register. "Shadow register" is unclear technical lingo. Just write "GPIO output registers are write-only" DT bindings are OS neutral, the fact that Linux and other OS:es need to cache ("shadow") this value is an implementation detail. Yours, Linus Walleij
On 27/01/2023 12:39, Leonard, Niall wrote: > > >> -----Original Message----- >> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> >> Sent: 26 January 2023 12:29 >> To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij >> <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob >> Herring <robh+dt@kernel.org>; Krzysztof Kozlowski >> <krzysztof.kozlowski+dt@linaro.org> >> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- >> kernel@vger.kernel.org >> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio >> bindings >> >> *External Message* - Use caution before opening links or attachments >> >> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: >>> From: Niall Leonard <nl250060@ncr.com> >> >> Subject: missing "wd,mbl-gpio:" prefix. >> >> Subject: drop second/last, redundant "bindings". The "dt-bindings" >> prefix is already stating that these are bindings. >> >>> >>> Added optional "no-input" property >> >> Missing full stop. >> >>> >>> Signed-off-by: Niall Leonard <nl250060@ncr.com> >>> --- >>> Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>> b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>> index 038c3a6a1f4d..9405f9dad522 100644 >>> --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>> +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>> @@ -18,6 +18,7 @@ Required properties: >>> >>> Optional properties: >>> - no-output: GPIOs are read-only. >>> + - no-input: GPIOs are write-only. Read is via a shadow register. >> >> Why this property is needed? Why driver cannot always use shadow >> register? >> > The shadow register is currently only used during the write operation. It is not available during the read operation. You just wrote above that reading is via shadow register, so how can it not be available for reads? Again, why you cannot always read via shadow register and need to make a property? You mean that for other GPIOs there is no shadow register at all? What changes between one board and another that justifies this property? > That is essentially the change I have > submitted. This does not answer me. I am asking why this change is justified in terms of Devicetree. > An alternative approach would have been to develop an entire new gpio driver similar to the 74xx driver, but I felt this approach was better. > >> Anyway, please convert the bindings to DT schema first (see writing-schema >> and example-schema). >> Documentation/devicetree/bindings/writing-schema.rst >> > The bindings for this driver are duplicated in a few files even though they use the same driver. > i.e. wd,mbl-gpio.txt, ni,169445-nand-gpio.txt, brcm,bcm6345-gpio.yaml So your changes here affect several bindings but you adjust only one? This won't work. > I don't know why these multiple bindings exist. It would perhaps make sense to remove these duplicate binding documentation files and replace with a single one for "basic-mmio-gpio". I happened to pick ". wd,mbl-gpio.txt", but I could have just as easily chosen one of the other 2. We usually keep same hardware in the same bindings. This might or might not map to same Linux driver (drivers are independent). All this hardware looks like having the same interface and same properties, so having one binding makes sense. Best regards, Krzysztof
On 29/01/2023 15:59, Krzysztof Kozlowski wrote: > *External Message* - Use caution before opening links or attachments > > On 27/01/2023 12:39, Leonard, Niall wrote: >> >> >>> -----Original Message----- >>> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> >>> Sent: 26 January 2023 12:29 >>> To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij >>> <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob >>> Herring <robh+dt@kernel.org>; Krzysztof Kozlowski >>> <krzysztof.kozlowski+dt@linaro.org> >>> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- >>> kernel@vger.kernel.org >>> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio >>> bindings >>> >>> *External Message* - Use caution before opening links or attachments >>> >>> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: >>>> From: Niall Leonard <nl250060@ncr.com> >>> >>> Subject: missing "wd,mbl-gpio:" prefix. >>> >>> Subject: drop second/last, redundant "bindings". The "dt-bindings" >>> prefix is already stating that these are bindings. >>> >>>> >>>> Added optional "no-input" property >>> >>> Missing full stop. >>> >>>> >>>> Signed-off-by: Niall Leonard <nl250060@ncr.com> >>>> --- >>>> Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>> b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>> index 038c3a6a1f4d..9405f9dad522 100644 >>>> --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>> +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>> @@ -18,6 +18,7 @@ Required properties: >>>> >>>> Optional properties: >>>> - no-output: GPIOs are read-only. >>>> + - no-input: GPIOs are write-only. Read is via a shadow register. >>> >>> Why this property is needed? Why driver cannot always use shadow >>> register? >>> >> The shadow register is currently only used during the write operation. It is not available during the read operation. > > You just wrote above that reading is via shadow register, so how can it > not be available for reads? Again, why you cannot always read via shadow > register and need to make a property? You mean that for other GPIOs > there is no shadow register at all? > The existing read method does not use the shadow register. static int bgpio_get(struct gpio_chip *gc, unsigned int gpio) { return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio)); } > What changes between one board and another that justifies this property? I have a couple of boards where the electronics engineer decided to only use the chip select line, so no read/write signal is connected. This means that reading the address activates the chip select and drives the contents of the data bus to the port. For example is someone reads the file /sys/kernel/debug/gpio this corrupts the port. So I have had to add this property to avoid that situation. If you are strongly against this then just reject it and I will look after it myself. I thought there may be others who would find this change useful. > >> That is essentially the change I have >> submitted. > > This does not answer me. I am asking why this change is justified in > terms of Devicetree. > How else would you suggest it was done ? I followed the existing pattern used previously for the "no-output" property. >> An alternative approach would have been to develop an entire new gpio driver similar to the 74xx driver, but I felt this approach was better. >> >>> Anyway, please convert the bindings to DT schema first (see writing-schema >>> and example-schema). >>> Documentation/devicetree/bindings/writing-schema.rst >>> >> The bindings for this driver are duplicated in a few files even though they use the same driver. >> i.e. wd,mbl-gpio.txt, ni,169445-nand-gpio.txt, brcm,bcm6345-gpio.yaml > > So your changes here affect several bindings but you adjust only one? > This won't work. > >> I don't know why these multiple bindings exist. It would perhaps make sense to remove these duplicate binding documentation files and replace with a single one for "basic-mmio-gpio". I happened to pick ". wd,mbl-gpio.txt", but I could have just as easily chosen one of the other 2. > > We usually keep same hardware in the same bindings. This might or might > not map to same Linux driver (drivers are independent). All this > hardware looks like having the same interface and same properties, so > having one binding makes sense. > > Best regards, > Krzysztof >
On Mon, Jan 30, 2023 at 01:20:55PM +0000, Leonard, Niall wrote: > On 29/01/2023 15:59, Krzysztof Kozlowski wrote: > > *External Message* - Use caution before opening links or attachments > > > > On 27/01/2023 12:39, Leonard, Niall wrote: > >> > >> > >>> -----Original Message----- > >>> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> > >>> Sent: 26 January 2023 12:29 > >>> To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij > >>> <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob > >>> Herring <robh+dt@kernel.org>; Krzysztof Kozlowski > >>> <krzysztof.kozlowski+dt@linaro.org> > >>> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- > >>> kernel@vger.kernel.org > >>> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio > >>> bindings > >>> > >>> *External Message* - Use caution before opening links or attachments > >>> > >>> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: > >>>> From: Niall Leonard <nl250060@ncr.com> > >>> > >>> Subject: missing "wd,mbl-gpio:" prefix. > >>> > >>> Subject: drop second/last, redundant "bindings". The "dt-bindings" > >>> prefix is already stating that these are bindings. > >>> > >>>> > >>>> Added optional "no-input" property > >>> > >>> Missing full stop. > >>> > >>>> > >>>> Signed-off-by: Niall Leonard <nl250060@ncr.com> > >>>> --- > >>>> Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + > >>>> 1 file changed, 1 insertion(+) > >>>> > >>>> diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> index 038c3a6a1f4d..9405f9dad522 100644 > >>>> --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> @@ -18,6 +18,7 @@ Required properties: > >>>> > >>>> Optional properties: > >>>> - no-output: GPIOs are read-only. > >>>> + - no-input: GPIOs are write-only. Read is via a shadow register. > >>> > >>> Why this property is needed? Why driver cannot always use shadow > >>> register? > >>> > >> The shadow register is currently only used during the write operation. It is not available during the read operation. > > > > You just wrote above that reading is via shadow register, so how can it > > not be available for reads? Again, why you cannot always read via shadow > > register and need to make a property? You mean that for other GPIOs > > there is no shadow register at all? > > > The existing read method does not use the shadow register. > > static int bgpio_get(struct gpio_chip *gc, unsigned int gpio) > { > return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio)); > } > > > What changes between one board and another that justifies this property? > > I have a couple of boards where the electronics engineer decided to only > use the chip select line, so no read/write signal is connected. This > means that reading the address activates the chip select and drives the > contents of the data bus to the port. This part makes sense as you explained the h/w. > For example is someone reads the > file /sys/kernel/debug/gpio this corrupts the port. So I have had to add > this property to avoid that situation. Not quite relevant to the DT binding being a Linux detail. > > If you are strongly against this then just reject it and I will look > after it myself. I thought there may be others who would find this > change useful. A property for a board level quirk is appropriate. You just need to explain that in the commit message rather than stating what the diff already tells us. Rob
On 30/01/2023 18:37, Rob Herring wrote: > *External Message* - Use caution before opening links or attachments > > On Mon, Jan 30, 2023 at 01:20:55PM +0000, Leonard, Niall wrote: >> On 29/01/2023 15:59, Krzysztof Kozlowski wrote: >>> *External Message* - Use caution before opening links or attachments >>> >>> On 27/01/2023 12:39, Leonard, Niall wrote: >>>> >>>> >>>>> -----Original Message----- >>>>> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> >>>>> Sent: 26 January 2023 12:29 >>>>> To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij >>>>> <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob >>>>> Herring <robh+dt@kernel.org>; Krzysztof Kozlowski >>>>> <krzysztof.kozlowski+dt@linaro.org> >>>>> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- >>>>> kernel@vger.kernel.org >>>>> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio >>>>> bindings >>>>> >>>>> *External Message* - Use caution before opening links or attachments >>>>> >>>>> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: >>>>>> From: Niall Leonard <nl250060@ncr.com> >>>>> >>>>> Subject: missing "wd,mbl-gpio:" prefix. >>>>> >>>>> Subject: drop second/last, redundant "bindings". The "dt-bindings" >>>>> prefix is already stating that these are bindings. >>>>> >>>>>> >>>>>> Added optional "no-input" property >>>>> >>>>> Missing full stop. >>>>> >>>>>> >>>>>> Signed-off-by: Niall Leonard <nl250060@ncr.com> >>>>>> --- >>>>>> Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + >>>>>> 1 file changed, 1 insertion(+) >>>>>> >>>>>> diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>>>> b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>>>> index 038c3a6a1f4d..9405f9dad522 100644 >>>>>> --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>>>> +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt >>>>>> @@ -18,6 +18,7 @@ Required properties: >>>>>> >>>>>> Optional properties: >>>>>> - no-output: GPIOs are read-only. >>>>>> + - no-input: GPIOs are write-only. Read is via a shadow register. >>>>> >>>>> Why this property is needed? Why driver cannot always use shadow >>>>> register? >>>>> >>>> The shadow register is currently only used during the write operation. It is not available during the read operation. >>> >>> You just wrote above that reading is via shadow register, so how can it >>> not be available for reads? Again, why you cannot always read via shadow >>> register and need to make a property? You mean that for other GPIOs >>> there is no shadow register at all? >>> >> The existing read method does not use the shadow register. >> >> static int bgpio_get(struct gpio_chip *gc, unsigned int gpio) >> { >> return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio)); >> } >> >>> What changes between one board and another that justifies this property? >> >> I have a couple of boards where the electronics engineer decided to only >> use the chip select line, so no read/write signal is connected. This >> means that reading the address activates the chip select and drives the >> contents of the data bus to the port. > > This part makes sense as you explained the h/w. > >> For example is someone reads the >> file /sys/kernel/debug/gpio this corrupts the port. So I have had to add >> this property to avoid that situation. > > Not quite relevant to the DT binding being a Linux detail. > >> >> If you are strongly against this then just reject it and I will look >> after it myself. I thought there may be others who would find this >> change useful. > > A property for a board level quirk is appropriate. You just need to > explain that in the commit message rather than stating what the diff > already tells us. > > Rob Thanks for reviewing. I will update the description in the patch introduction to indicate this a board level quirk and the reasoning behind it. Regards, Niall Leonard
diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt index 038c3a6a1f4d..9405f9dad522 100644 --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt @@ -18,6 +18,7 @@ Required properties: Optional properties: - no-output: GPIOs are read-only. + - no-input: GPIOs are write-only. Read is via a shadow register. Examples: gpio0: gpio0@e0000000 {