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. > > * 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. > > If you think those suggestions are OK, I can put together a series to > fix this. I think we need to hear from Rob before we proceed tbh, as he is the original author and should have a chance to voice his opinion. -- Lee Jones Linaro ST-Ericsson Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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
