On Wednesday, August 12, 2015 at 11:09:15 PM, Simon Glass wrote: > Hi Marek, > > On 12 August 2015 at 08:40, Marek Vasut <ma...@denx.de> wrote: > > On Wednesday, August 12, 2015 at 03:55:59 PM, Simon Glass wrote: > >> Hi Marek, > >> > >> On 12 August 2015 at 07:53, Marek Vasut <ma...@denx.de> wrote: > >> > On Wednesday, August 12, 2015 at 03:51:07 PM, Simon Glass wrote: > >> >> Hi Marek, > >> >> > >> >> On 12 August 2015 at 07:48, Marek Vasut <ma...@denx.de> wrote: > >> >> > On Wednesday, August 12, 2015 at 03:04:15 PM, Simon Glass wrote: > >> >> >> Hi Marek, > >> >> > > >> >> > Hi! > >> >> > > >> >> > [...] > >> >> > > >> >> >> >> >> > Why are you passing the @freq into get_mmc_clk() ? > >> >> >> >> >> > Shouldn't you call some clock framework function to > >> >> >> >> >> > determine the input frequency of the DWMMC block from > >> >> >> >> >> > within the get_mmc_clk() implementation instead ? What do > >> >> >> >> >> > you think please ? > >> >> >> >> >> > >> >> >> >> >> Well, yes. If such a clock frame work existed I would call > >> >> >> >> >> it > >> >> >> >> >> > >> >> >> >> >> :-) We do have a uclass now so we are getting there. > >> >> >> >> > > >> >> >> >> > Excellent, so do you really need this kind of patch ? :) Why > >> >> >> >> > don't you make just some kind of function -- > >> >> >> >> > get_dwmmc_clock() -- and call it instead ? > >> >> >> >> > >> >> >> >> This is sort-of what is happening. It is calling a function in > >> >> >> >> the host controller - i.e. the SoC's MMC controller. It is one > >> >> >> >> step closer to knowing the input clock to the dwmmc input > >> >> >> >> clock. Note that it is not the clock of the MMC bus itself, > >> >> >> >> but the input clock to the dwmmc logic block. > >> >> >> > > >> >> >> > I don't think I quite understand what you mean here. We're > >> >> >> > talking about obtaining the frequency of the clock which go > >> >> >> > into the DWMMC IP block, right ? > >> >> >> > > >> >> >> > So, if you implement a function, say -- > >> >> >> > dwmmc_get_upstream_clock() -- and call it from within the > >> >> >> > implementation of the > >> >> >> > .get_mmc_clk(), which is specific for that particular chip of > >> >> >> > yours*, you don't need this patch. Or am I really missing > >> >> >> > something fundamental ? > >> >> >> > > >> >> >> > *the .get_mmc_clk() is specific to a chip, see for example > >> >> >> > exynos_dw_mmc.c > >> >> >> > >> >> >> The purpose of the existing code (before my change) is to find out > >> >> >> the input frequency of the IP block. By knowing this, the dw_mmc > >> >> >> driver can work out what divisor it needs to achieve a particular > >> >> >> MMC bus clock. > >> >> >> > >> >> >> The implementation of get_mmc_clk() (which will be in the > >> >> >> SoC-specific MMC driver) is indeed the place where the clock is > >> >> >> figured out. My only change is to add a parameter which is the > >> >> >> desired bus clock. This parameter can be ignored, but for > >> >> >> implementations which can select the source clock such that it > >> >> >> matches this bus clock, then they can do this and dw_mmc can just > >> >> >> use bypass mode. > >> >> > > >> >> > I see now, this wasn't really clear from the patch description. > >> >> > Shouldn't you introduce another callback for this purpose then, > >> >> > like .set_mmc_clk() instead ? > >> >> > >> >> We could do, but I don't like introducing another interface for one > >> >> client. Also I think the right solution is to move it to use the > >> >> generic clock infrastructure, when it exists (well we have it, but > >> >> nothing uses it yet). > >> > > >> > OK, but making a .get_mmc_clk() function actually configure something > >> > is a behavior I wouldn't expect from a getter function. It's a bit odd > >> > and illogical in my opinion. > >> > >> Yes fair enough, it is odd. I did start an MMC uclass so perhaps that > >> will lead to a better solution. It's unfortunately that dw_mmc need > >> its own callback infrastructure. > > > > I hope we can iron that out shortly. The good thing is that you now have > > a board with the DWMMC and SoCFPGA also has one, so we have at least two > > pairs of eyes on it. > > > > Also, what do you prefer to do about this patch ? Shall we go with the > > .set_mmc_clock() callback and be done with it or do you want to stick > > with the current approach ? I'm inclined to the former as it's less > > confusing in my opinion. > > Let's revisit it when I get back to the rockchip series.
I just checked the socfpga and I see I can use this functionality too :) _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
