Re: [RFC 0/6] pinctrl: samsung: Remove static platform-specific data
On 09/21/2012 01:31 PM, Tomasz Figa wrote: On Friday 21 of September 2012 12:40:35 Stephen Warren wrote: On 09/20/2012 02:53 AM, Tomasz Figa wrote: This RFC series is a work on replacing static platform-specific data in pinctrl-samsung driver with data dynamically parsed from device tree. ... It aims at reducing the SoC-specific part of the driver and thus the amount of modifications to driver sources when adding support for next SoCs (like Exynos4x12). Furthermore, moving definitions of pin banks to device tree will allow to simplify GPIO and GEINT specification to a format similar to used previously by gpiolib-based implementation, using a phandle to the bank and pin index inside the bank, e.g. gpios = gpa1 4 0; interrupt-parent = gpa1; interrupts = 4 0; I don't think those two are correlated; the GPIO specifier format could just as easily be bank pin irrespective of whether the pinctrl driver contains SoC-specific tables or not. Correct me if I'm wrong, but each bank needs to have its own subnode to be able to address pins like this. That was the starting point of the whole series and the idea that if all the banks (which are SoC-specific) have to be defined anyway, maybe it wouldn't be too bad to put all the SoC-specific parameters there too. If you write your own custom .xlate function, I think you can do basically anything you want; all of the following are possible, I believe: a) Single DT node covering all banks, with GPIO specifier being n where n is some linearized GPIO ID across all banks. b) Single DT node covering all banks, with GPIO specifier being b n where b is the bank number, and n is the GPIO ID within the bank (xlate would presumably calculate (b * MAX_GPIOS_PER_BANK) + n and up with the same data as in (a) above. c) One DT node per bank, one gpio_chip registered per node, with the GPIO specifier being n where n is the GPIO ID within the bank the phandle points at. d) One DT node per bank, all contained within a single parent DT node, one gpio_chip registered per node (one for each bank node, and one for the parent node), with GPIO phandles pointing at the parent node, with GPIO specifier in the format of either (a) or (b) above, and the top-level node's .xlate returning a different gpio_chip (for one of the child bank-specific nodes) rather than the parent chip. At least, IIRC, Grant Likely was going to extend a gpio_chip's .xlate to be able to return a different chip; I'm not sure if that was implemented yet or not. -- To unsubscribe from this list: send the line unsubscribe linux-samsung-soc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC 0/6] pinctrl: samsung: Remove static platform-specific data
On 09/20/2012 02:53 AM, Tomasz Figa wrote: This RFC series is a work on replacing static platform-specific data in pinctrl-samsung driver with data dynamically parsed from device tree. Hmm. I tend to think this is exactly the opposite of the correct direction; you end up wasting a whole ton of time during the boot process parsing data out of the device tree only to end up with exactly the same tables that you would have just put into the kernel anyway. Is it really likely that future SoCs will change information such as the width of the pullup/pulldown bitfield, but not change anything else that's not already in this binding. If that isn't the case, the binding won't be complete enough to describe any new features on future SoCs anyway. It aims at reducing the SoC-specific part of the driver and thus the amount of modifications to driver sources when adding support for next SoCs (like Exynos4x12). Furthermore, moving definitions of pin banks to device tree will allow to simplify GPIO and GEINT specification to a format similar to used previously by gpiolib-based implementation, using a phandle to the bank and pin index inside the bank, e.g. gpios = gpa1 4 0; interrupt-parent = gpa1; interrupts = 4 0; I don't think those two are correlated; the GPIO specifier format could just as easily be bank pin irrespective of whether the pinctrl driver contains SoC-specific tables or not. Any comments are welcome. TODO: - bindings documentation That's unfortunate; it would be the most interesting part to review. I guess I'll try to work out the binding from the examples in patch 6. -- To unsubscribe from this list: send the line unsubscribe linux-samsung-soc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC 0/6] pinctrl: samsung: Remove static platform-specific data
Hi Stephen, Thanks for your comments. On Friday 21 of September 2012 12:40:35 Stephen Warren wrote: On 09/20/2012 02:53 AM, Tomasz Figa wrote: This RFC series is a work on replacing static platform-specific data in pinctrl-samsung driver with data dynamically parsed from device tree. Hmm. I tend to think this is exactly the opposite of the correct direction; you end up wasting a whole ton of time during the boot process parsing data out of the device tree only to end up with exactly the same tables that you would have just put into the kernel anyway. Yes, I'm aware that parsing all those information from device tree won't be free. I have even considering simplifying the binding to something like samsung,pin-bank = offset count func pud drv conpdn pudpdn; listing widths of fields in fixed order, with some fields allowed to be zero, meaning that given bank doesn't support this control. It would simplify the parsing to just iterating over a table under a single property. What do you think? I have decided to post the original variant to get some comments earlier, as I already had all the rest of patches based on it. Is it really likely that future SoCs will change information such as the width of the pullup/pulldown bitfield, but not change anything else that's not already in this binding. If that isn't the case, the binding won't be complete enough to describe any new features on future SoCs anyway. Looking at the history of Samsung SoCs and specifics of this subsystem, there isn't much likely to change other than the bindings already account for (and the binding represents whatever the driver accounts for). It aims at reducing the SoC-specific part of the driver and thus the amount of modifications to driver sources when adding support for next SoCs (like Exynos4x12). Furthermore, moving definitions of pin banks to device tree will allow to simplify GPIO and GEINT specification to a format similar to used previously by gpiolib-based implementation, using a phandle to the bank and pin index inside the bank, e.g. gpios = gpa1 4 0; interrupt-parent = gpa1; interrupts = 4 0; I don't think those two are correlated; the GPIO specifier format could just as easily be bank pin irrespective of whether the pinctrl driver contains SoC-specific tables or not. Correct me if I'm wrong, but each bank needs to have its own subnode to be able to address pins like this. That was the starting point of the whole series and the idea that if all the banks (which are SoC-specific) have to be defined anyway, maybe it wouldn't be too bad to put all the SoC-specific parameters there too. Any comments are welcome. TODO: - bindings documentation That's unfortunate; it would be the most interesting part to review. I guess I'll try to work out the binding from the examples in patch 6. Sorry about that. I thought the examples would be sufficient. Still, I was focused at getting comments about the idea of moving such data to DT in general, not the bindings, which are most likely to change, in particular. Best regards, Tomasz Figa -- To unsubscribe from this list: send the line unsubscribe linux-samsung-soc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC 0/6] pinctrl: samsung: Remove static platform-specific data
On Thu, Sep 20, 2012 at 10:53 AM, Tomasz Figa t.f...@samsung.com wrote: This RFC series is a work on replacing static platform-specific data in pinctrl-samsung driver with data dynamically parsed from device tree. Please include Stephen Warren on this series, he know his way around pinctrl - devicetree better than anyone else. (I'll look and see if I can see something that sticks out...) Yours, Linus Walleij -- To unsubscribe from this list: send the line unsubscribe linux-samsung-soc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
