Messages in this thread | | | Subject | Re: [PATCH v2 2/3] hwmon: (aspeed-pwm-tacho) Deassert reset in probe | From | Guenter Roeck <> | Date | Fri, 3 Nov 2017 03:11:03 -0700 |
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On 11/02/2017 07:32 PM, Joel Stanley wrote: > On Fri, Nov 3, 2017 at 1:54 AM, Guenter Roeck <linux@roeck-us.net> wrote: >> On Thu, Nov 02, 2017 at 02:53:48PM +1100, Joel Stanley wrote: >>> The ASPEED SoC must deassert a reset in order to use the PWM/tach >>> peripheral. >>> >> Again, you claim that the current driver would not work at all, which >> is simply not correct. It doesn't work if the chip wasn't taken out >> of reset by other means. This doesn't take into account situations and >> hardware where the chip is taken out of reset automatically at boot, h >> or by the ROM monitor/BIOS. It assumes that the reset pin can _always_ >> be controlled by software. > > The reset is internal to the SoC. There is no pin to speak of, just a > wire inside the SoC, so it can always be controlled by software. > > There's SoC does not release any resets automatically; the default > value on boot is for the reset to be asserted and this is not > configurable. > >> Similar, it forces the chip into reset when the driver is removed, >> which is even worse. Unload the driver, and no more fan control ? >> Really ? Then why is there an autonomous chip for fan control >> to start with ? This is questionable even if the reset pin is >> optional. > > Similarly, the PWM/Tach unit is inside the SoC; it's not an external device. > > It would be strange to remove the driver and expect the system to keep > operating normally. > >> You'll have to make reset handling optional for me to accept it. >> I am quite sure that I said that before. > > Please reconsider in light of the details above. It does not make any > sense to build a system without this reset. >
So you are saying that this driver never worked ? Hard to believe. I'll need input from other users.
Guenter
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