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Message-ID: <20151001122555.GV3214@x1>
Date: Thu, 1 Oct 2015 13:25:55 +0100
From: Lee Jones <lee@...nel.org>
To: Eric Anholt <eric@...olt.net>
Cc: linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Stephen Warren <swarren@...dotorg.org>,
Stephen Boyd <sboyd@...eaurora.org>,
Mike Turquette <mturquette@...libre.com>,
devicetree@...r.kernel.org
Subject: Re: [PATCH v3 4/4] ARM: bcm2835: Switch to using the new clock
driver support.
On Mon, 28 Sep 2015, Eric Anholt wrote:
> This will give us the ability to set the pixel and HDMI state machine
> clocks for the VC4 KMS driver, change the CPU frequency, and
> potentially gate clocks in the future (once we also write a power
> domain driver). It also gives the uart an explicit clock reference,
> so that we don't need to change the physical addresses of the old
> fixed clk_bcm2835.c clocks for Raspberry Pi 2 port.
>
> Two clocks get their frequencies updated as a result of this. One is
> uart's apb_pclk, which was previously accidentally grabbing the fixed
> uart0_pclk due to the apb_pclk not having clk_register_clkdev()
> called. The uart doesn't seem to do anything with apb_pclk other than
> make sure it's on, so that appears safe (also, as far as I can see,
> the apb clock is actually the same as the VPU clock). The other is
> EMMC, which according to the docs was supposed to be in the 50-100Mhz
> range, but it turns out the firmware needed to change to running it at
> the 250Mhz core clock speed to avoid a bug in clock domain crossing.
>
> Additionally, anything using BCM2835_CLOCK_VPU will now have a correct
> clock rate if the user configures the boot-time core clock speed using
> config.txt.
>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> Acked-by: Stephen Warren <swarren@...dotorg.org>
> ---
> arch/arm/boot/dts/bcm2835.dtsi | 52 +++++++++++++++++++++++-------------------
> 1 file changed, 28 insertions(+), 24 deletions(-)
Couple of small nits.
> diff --git a/arch/arm/boot/dts/bcm2835.dtsi b/arch/arm/boot/dts/bcm2835.dtsi
> index 301c73f..a6a55b7 100644
> --- a/arch/arm/boot/dts/bcm2835.dtsi
> +++ b/arch/arm/boot/dts/bcm2835.dtsi
> @@ -1,4 +1,5 @@
> #include <dt-bindings/pinctrl/bcm2835.h>
> +#include <dt-bindings/clock/bcm2835.h>
> #include "skeleton.dtsi"
>
> / {
> @@ -21,6 +22,10 @@
> compatible = "brcm,bcm2835-system-timer";
> reg = <0x7e003000 0x1000>;
> interrupts = <1 0>, <1 1>, <1 2>, <1 3>;
> + /* This could be a reference to BCM2835_CLOCK_TIMER,
> + * but we don't have the driver using the common clock
> + * support yet.
> + */
Nit: Please use correct multi-line comment formatting.
>From Documentation/CodingStyle:
/*
* This is the preferred style for multi-line
* comments in the Linux kernel source code.
* Please use it consistently.
*
* Description: A column of asterisks on the left side,
* with beginning and ending almost-blank lines.
*/
> clock-frequency = <1000000>;
> };
>
> @@ -57,6 +62,17 @@
> reg = <0x7e100000 0x28>;
> };
>
> + clocks: cprman@...01000 {
> + compatible = "brcm,bcm2835-cprman";
> + #clock-cells = <1>;
> + reg = <0x7e101000 0x2000>;
> +
> + /* CPRMAN derives everything from the platform's
> + * oscillator.
> + */
As above.
> + clocks = <&clk_osc>;
> + };
> +
> rng@...04000 {
> compatible = "brcm,bcm2835-rng";
> reg = <0x7e104000 0x10>;
> @@ -96,7 +112,9 @@
> compatible = "brcm,bcm2835-pl011", "arm,pl011", "arm,primecell";
> reg = <0x7e201000 0x1000>;
> interrupts = <2 25>;
> - clock-frequency = <3000000>;
> + clocks = <&clocks BCM2835_CLOCK_UART>,
> + <&clocks BCM2835_CLOCK_VPU>;
> + clock-names = "uartclk", "apb_pclk";
> arm,primecell-periphid = <0x00241011>;
> };
>
> @@ -115,7 +133,7 @@
> compatible = "brcm,bcm2835-spi";
> reg = <0x7e204000 0x1000>;
> interrupts = <2 22>;
> - clocks = <&clk_spi>;
> + clocks = <&clocks BCM2835_CLOCK_VPU>;
> #address-cells = <1>;
> #size-cells = <0>;
> status = "disabled";
> @@ -125,7 +143,7 @@
> compatible = "brcm,bcm2835-i2c";
> reg = <0x7e205000 0x1000>;
> interrupts = <2 21>;
> - clocks = <&clk_i2c>;
> + clocks = <&clocks BCM2835_CLOCK_VPU>;
> #address-cells = <1>;
> #size-cells = <0>;
> status = "disabled";
> @@ -135,7 +153,7 @@
> compatible = "brcm,bcm2835-sdhci";
> reg = <0x7e300000 0x100>;
> interrupts = <2 30>;
> - clocks = <&clk_mmc>;
> + clocks = <&clocks BCM2835_CLOCK_EMMC>;
> status = "disabled";
> };
>
> @@ -143,7 +161,7 @@
> compatible = "brcm,bcm2835-i2c";
> reg = <0x7e804000 0x1000>;
> interrupts = <2 21>;
> - clocks = <&clk_i2c>;
> + clocks = <&clocks BCM2835_CLOCK_VPU>;
> #address-cells = <1>;
> #size-cells = <0>;
> status = "disabled";
> @@ -165,28 +183,14 @@
> #address-cells = <1>;
> #size-cells = <0>;
>
> - clk_mmc: clock@0 {
> - compatible = "fixed-clock";
> - reg = <0>;
> - #clock-cells = <0>;
> - clock-output-names = "mmc";
> - clock-frequency = <100000000>;
> - };
> -
> - clk_i2c: clock@1 {
> + /* The oscillator is the root of the clock tree. */
> + clk_osc: clock@3 {
> compatible = "fixed-clock";
> - reg = <1>;
> + reg = <3>;
> #clock-cells = <0>;
> - clock-output-names = "i2c";
> - clock-frequency = <250000000>;
> + clock-output-names = "osc";
> + clock-frequency = <19200000>;
> };
>
> - clk_spi: clock@2 {
> - compatible = "fixed-clock";
> - reg = <2>;
> - #clock-cells = <0>;
> - clock-output-names = "spi";
> - clock-frequency = <250000000>;
> - };
> };
> };
--
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