On 02/22/2017 12:00 PM, Jonas Gorski wrote: > On 22 February 2017 at 19:26, Mark Brown <broonie@xxxxxxxxxx> wrote: >> On Wed, Feb 22, 2017 at 02:19:38PM +0100, Jonas Gorski wrote: >>> Instead of requiring the hsspi clock to have a rate, allow using a second >>> clock for providing the Hz rate, which is probably more correct anyway. >> >> I'm sorry but I just can't follow the logic here at all - why would we >> use "a second clock" to get the rate of a clock and why would that be >> more correct? There's a few steps in the reasoning missing here I >> think! > > The PLL rate is hardcoded in the original broadcom code (with > #if-deffery for different SoCs); when I added support for the HSSPI > controller in upstream linux, I thought "hey, let's put it as the rate > of the (gateable) HSSPI clock, then I don't need to pass it as > platform data". Part of the issue is also that bcm63xx has its own clk > code, so couldn't use clk lookups even if I wanted. > > The register for the gated clock control is calld blkEnables (so might > be just power gating?), and the #define for the rate is called > HS_SPI_PLL_FREQ, which at least gives me the impression these could be > two different things/clocks. Whether it's a separate PLL from the > gated clock or not someone with actual hardware knowledge would have > to tell. I looked at the HSSPI datasheet again and there are indeed two separate input clock signals to the HSSPI block, one which is a PLL clock and that is used to control the external SPI output/input clock. The other clock is the UBUS register interface clock and also clock gates the block when unused. So with that: Acked-by: Florian Fainelli <f.fainelli@xxxxxxxxx> > > To (eventually) get rid of bcm63xx's own clk code and replace it with > a proper clock driver with lookups and stuff, it would make it much > easier to just move the PLL_FREQ into a separate fixed-rate clock, as > it is the only clock in the bcm63xx code that has a rate attached and > is gated. So I wouldn't need to create composite clocks to and could > just directly make it a simple gated-clock driver. > > Hope that explanation helps. > > > Regards > Jonas > -- Florian -- 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
