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. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
