On 2016년 08월 28일 01:33, Krzysztof Kozlowski wrote: > On Thu, Aug 25, 2016 at 03:57:18PM +0900, Chanwoo Choi wrote: >> This patch sets the clock rate for DREX (DRAM Express) block >> on exynos5422-odroidxu3 board. In the exynos5422 TRM, >> DRAM clocks use BPLL clock and CMU_CDREX generates >> the 800MHz DRAM clock. >> > >>From the commit message I don't get two things: > 1. Why setting this on XU3-family of boards, not all 542x/5800? I have the only xu3 board. I cannot test it on other boards. > 2. Why this is needed? The commit msg lacks the answer to the "why". In the exynos5422's TRM, CMU_CDREX generates the 800MHz DRAM clock as above commit message. But, I'm missing what there is different before applying this patch. I add comment why we should set the clock rate for DRAM on below. > >> [clk_summary on exynos5422-odroidxu3 board] >> fout_bpll 0 0 800000000 0 0 >> mout_bpll 0 0 800000000 0 0 >> mout_mclk_cdrex 0 0 800000000 0 0 >> dout_pclk_core_mem 0 0 200000000 0 0 >> dout_sclk_cdrex 0 0 800000000 0 0 >> > > What is the purpose of this dump of clk_summary? Is it a state before or > after the change? After it is quite obvious that it should have > 800MHz... I'm missing the difference before applying this patch. As I mentioned on v1[1] patch, if I don't set the clock rate for CDREX, the default clock is 825MHz instead of 800MHz. So, I set the clock rate on this patch. [1] https://lkml.org/lkml/2016/8/22/255 If I don't apply this patch, the DREX clock is 825MHz. fout_bpll 0 0 825000000 0 0 mout_bpll 0 0 825000000 0 0 mout_mclk_cdrex 0 0 825000000 0 0 dout_pclk_core_mem 0 0 206250000 0 0 dout_sclk_cdrex 0 0 825000000 0 0 dout_clk2x_phy0 0 0 825000000 0 0 dout_aclk_cdrex1 0 0 412500000 0 0 dout_pclk_cdrex 0 0 103125000 0 0 dout_cclk_drex0 0 0 412500000 0 0 If you want to edit the commit message, I'll resend the v3 patch. Best Regards, Chanwoo Choi > > Best regards, > Krzysztof > >> Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx> >> --- >> arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi >> index d56253049ccb..fd3f67c72039 100644 >> --- a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi >> +++ b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi >> @@ -229,6 +229,11 @@ >> status = "okay"; >> }; >> >> +&clock { >> + assigned-clocks = <&clock CLK_DOUT_SCLK_CDREX>; >> + assigned-clock-rates = <800000000>; >> +}; >> + >> &clock_audss { >> assigned-clocks = <&clock_audss EXYNOS_MOUT_AUDSS>, >> <&clock_audss EXYNOS_MOUT_I2S>, >> -- >> 1.9.1 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- > To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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