linux-kernel - Re: [PATCH 1/2] ARM64: dts: rockchip: add sdhci/emmc for rk3399

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Message-ID: <20160511223114.GA65449@google.com>
Date:	Wed, 11 May 2016 15:31:14 -0700
From:	Brian Norris <briannorris@...omium.org>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, dianders@...omium.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	h <hl@...k-chips.com>
Subject: Re: [PATCH 1/2] ARM64: dts: rockchip: add sdhci/emmc for rk3399

On Wed, May 11, 2016 at 09:17:38AM +0800, Shawn Lin wrote:
> + Huang Lin
> 
> On 2016/5/11 8:02, Brian Norris wrote:
> >The bindings for rk3399's SDHCI + eMMC PHY have been accepted, so let's
> >support eMMC now.
> >
> >Note that 'rockchip,rk3399-sdhci-5.1' is not documented, but per Heiko's
> >previous suggestion, we don't want to clutter the arasan doc, and it's
> >just a precautionary measure to have it.
> >
> >Signed-off-by: Brian Norris <briannorris@...omium.org>
> >---
> > arch/arm64/boot/dts/rockchip/rk3399.dtsi | 23 ++++++++++++++++++++++-
> > 1 file changed, 22 insertions(+), 1 deletion(-)
> >
> >diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >index 46f325a143b0..947d1221592d 100644
> >--- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >+++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >@@ -215,6 +215,17 @@
> > 		status = "disabled";
> > 	};
> >
> >+	sdhci: sdhci@...30000 {
> >+		compatible = "rockchip,rk3399-sdhci-5.1", "arasan,sdhci-5.1";
> >+		reg = <0x0 0xfe330000 0x0 0x10000>;
> >+		interrupts = <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
> >+		clocks = <&cru SCLK_EMMC>, <&cru ACLK_EMMC>;
> 
> sdhci doesn't call clk_set_rate to explicitly assign clk_xin to 200MHz
> as it always assumes sdhci controller should meet the highest speed of
> each timing mode. And the internal divider will be used. So IMHO,
> clk-rockchip for 3399 *haven't* made clk_xin to be 200MHz. Let's assign
> the clk stuff to make sure it's 200MHz.
> 
> Another problem is that emmc_phy contains a configuration which should
> be consistent with clk_out(namely clk_xin/internal dividor). Now I don't
> submit unpstream patchset to expose these configurarion, but in
> prevention of some misleading, I think it's better to to it.
> 
> How about adding these?
> 
> assigned-clocks = <&cru SCLK_EMMC>;
> assigned-clock-parents = <&cru PLL_CPLL>; //may not need
> assigned-clock-rates = <200000000>;

Makes sense. Will add these.

> Still you limit your clk_out by adding max-frequency in dts for
> specific requirment.
> 
> We here manually assigne the clk_xin to be 200MHz, so defaultly
> when it's runing in HS200/HS400(ES) mode, internal divider won't
> be used(by-pass mode). So the clk jitter is better when by-passing the
> clock.
> 
> Thanks.

Brian