On Tue, Aug 27, 2013 at 9:08 AM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > On Tue, 27 Aug 2013, Mark Rutland wrote: > >> On Tue, Aug 27, 2013 at 09:06:35AM +0100, Lee Jones wrote: >> > On Fri, 23 Aug 2013, Mark Rutland wrote: >> > >> > > On Fri, Aug 23, 2013 at 08:56:07AM +0100, Lee Jones wrote: >> > > > I had a short chat with Rob last night about this. I'm going to loop >> > > > him in to the conversation, as he wrote the binding. >> > > > >> > > > > > When most of the other clocks that we deal with are being requested, >> > > > > > they rely on being index zero: >> > > > > > >> > > > > > drivers/i2c/busses/i2c-nomadik.c: dev->clk = clk_get(&adev->dev, NULL); >> > > > > >> > > > > Look at drivers/clk/clkdev.c, there's some fuzzy matching >> > > > > involved when you pass NULL as connection id. >> > > > >> > > > Yes, I've been looking at that. This is why it works currently. I >> > > > think I need to change all of the drivers to specify which clock they >> > > > want. At the moment that 'fuzzy matching' is what's saving us. If >> > > > anyone were to change our DTS file to match what the binding says, >> > > > then it would cease to work. I'm guessing this is the same for all >> > > > other DTS files too: >> > > >> > > I think if anything, the binding document(s) should be updated to >> > > describe that apb_pclk is referred to by name, and the names of the >> > > other clocks should be described in the specific device bindings. We can >> > > then modify the drivers which grab clock 0 to explicitly grab the first >> > > clock by name, and backwards compatibility should not be broken. >> > > >> > > I don't believe any other OS has implemented the common clock bindings, >> > > and we've never supported the binding as described. Let's correct the >> > > de-facto standard into a standard by decree. >> > >> > I think we need to respect, or at least take into consideration the >> > reason for the original 'de-facto' standard. Other OSes shouldn't be >> > forced to provide a named clock request in order to obtain >> > 'apb_pclk'. If the binding says it should be first, then perhaps we >> > should do just that. It's simply a matter of naming all subsequent >> > clocks related to AMBA devices. >> >> Ideally, yes. However, we have to be careful to not break compatibility. >> >> I took a look at existing primecell drivers and what they do. The >> situation isn't so bad (with the exception of the >> half-dt/half-platform-code mess): >> >> * Some don't deal with clocks at all (no clk* in the driver). pl320 is >> in the ecx-common dtsi with only apb_pclk but has no binding >> defined. Some have no clocks defined in the dt and are presumably few >> clocks by platform data or are non-functional. >> >> I'm not sure how these DTs are going to be supported if and when we >> remove the platform data they depend upon. If we're really going to do >> that, then they are clearly not supported as-is long term. >> >> * The pl022 driver grabs the first clock to figure out the rate of the >> spi bus (assuming it is SSPCLK). The SSPCLK input is not defined in >> the binding. The ste-u300 dts has two clock-names, "apb_pclk" and >> "spi_clk" (in that order), but they refer to the same clock. >> >> Given the existing driver simply grabs the first clock and they're >> both the same, we could re-order the names and make the driver grab >> the second clock. That wouldn't break backwards compatibility with the >> sole dts file we have using the binding, though this assumes no-one >> else has a dt lying around with different clocks. >> >> * pl010 grabs the first clock given to it to figure out the uart rate >> (assuming it is UARTCLK), but it's only in integratorap.dts, without >> clocks, and is presumably fed by platform data. There is no binding >> document. >> >> pl011 grabs the first clock given to figure out the UART rate >> (assuming it is UARTCLK). The binding explicitly states it's only >> given apb_pclk, despite UARTCLK and PCLK being separate inputs to the >> IP block. >> >> These two bindings don't describe the hardware, and should be fixed. >> The only way I can think to make this work without breaknig backwards >> compatibility would be to try to grab the second clock and then fall >> back to the first if there isn't one. The other option is to break >> backwards compatibility, but I'm not sure that's much of an option. This was an oversight since highbank has a single clock. But yes, this should be 2 clocks. It should be fixed and in a compatible way please. >> * pl111 has no driver or binding in mainline, but appears in dts files. >> Those dts files clcdclk and apb_pclk, in that order. We could fix >> those before a driver starts using them. I think this was waiting for some generic display bindings? Pawel may know. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
