On 9/9/21 3:45 AM, Maxime Ripard wrote: > On Fri, Sep 03, 2021 at 10:21:13AM -0500, Samuel Holland wrote: >> On 9/3/21 9:50 AM, Maxime Ripard wrote: >>> Hi, >>> >>> On Wed, Sep 01, 2021 at 12:39:44AM -0500, Samuel Holland wrote: >>>> This patch series adds a CCU driver for the RTC in the H616 and R329. >>>> The extra patches at the end of this series show how it would be >>>> explanded to additional hardware variants. >>>> >>>> The driver is intended to support the existing binding used for the H6, >>>> but also an updated binding which includes all RTC input clocks. I do >>>> not know how to best represent that binding -- that is a major reason >>>> why this series is an RFC. >>>> >>>> A future patch series could add functionality to the driver to manage >>>> IOSC calibration at boot and during suspend/resume. >>>> >>>> It may be possible to support all of these hardware variants in the >>>> existing RTC clock driver and avoid some duplicate code, but I'm >>>> concerned about the complexity there, without any of the CCU >>>> abstraction. >>>> >>>> This series is currently based on top of the other series I just sent >>>> (clk: sunxi-ng: Lifetime fixes and module support), but I can rebase it >>>> elsewhere. >>> >>> I'm generally ok with this, it makes sense to move it to sunxi-ng, >>> especially with that other series of yours. >>> >>> My main concern about this is the split driver approach. We used to have >>> that before in the RTC too, but it was mostly due to the early clock >>> requirements. With your previous work, that requirement is not there >>> anymore and we can just register it as a device just like the other >>> clock providers. >> >> That's a good point. Originally, I had this RTC CCU providing osc24M, so >> it did need to be an early provider. But with the current version, we >> could have the RTC platform driver call devm_sunxi_ccu_probe. That does >> seem cleaner. >> >> (Since it wasn't immediately obvious to me why this works: the only >> early provider remaining is the sun5i CCU, and it doesn't use the sun6i >> RTC driver.) >> >>> And since we can register all those clocks at device probe time, we >>> don't really need to split the driver in two (and especially in two >>> different places). The only obstacle to this after your previous series >>> is that we don't have of_sunxi_ccu_probe / devm_sunxi_ccu_probe >>> functions public, but that can easily be fixed by moving their >>> definition to include/linux/clk/sunxi-ng.h >> >> Where are you thinking the clock definitions would go? We don't export >> any of those structures (ccu_mux, ccu_common) or macros >> (SUNXI_CCU_GATE_DATA) in a public header either. > > Ah, right... > >> Would you want to export those? That seems like a lot of churn. Or would >> we put the CCU descriptions in drivers/clk/sunxi-ng and export a >> function that the RTC driver can call? (Or some other idea?) > > I guess we could export it. There's some fairly big headers in > include/linux/clk already (tegra and ti), it's not uAPI and we do have > reasons to do so, so I guess it's fine. > > I'd like to avoid having two drivers for the same device if possible, > especially in two separate places. This creates some confusion since the > general expectation is that there's only one driver per device. There's > also the fact that this could lead to subtle bugs since the probe order > is the link order (or module loading). I don't think there can be two "struct device"s for a single OF node. So if the CCU part is in drivers/clk/sunxi-ng, the CCU "probe" function would have to be called from the RTC driver. Since there has to be cooperation anyway, I don't think there would be any ordering problems. > And synchronizing access to registers between those two drivers will be > hard, while we could just share the same spin lock between the RTC and > clock drivers if they are instanciated in the same place. While the RTC driver currently shares a spinlock between the clock part and the RTC part, there isn't actually any overlap in register usage between the two. So there doesn't need to be any synchronization. Regards, Samuel
