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- From 9120234bb37043477ef69fec8c03c3731ed6861f Mon Sep 17 00:00:00 2001
- From: Phil Elwell <phil@raspberrypi.org>
- Date: Mon, 25 Jan 2016 09:12:06 +0000
- Subject: [PATCH] BCM270X_DT: Add sdio_overclock parameter to sdio overlay
- The sdio_overclock parameter is like the overclock_50 parameter, i.e.
- it sets an alternate frequency (in MHz) to use when the MMC framework
- requests 50MHz, except that it applies to the SDIO bus.
- Be aware that the actual frequencies achievable are limited to even integer
- divisions of 250MHz, and that the driver will round up to include fractions
- (e.g. 62 will include 62.5) but then round down to the nearest frequency.
- In other words, the chosen frequency is the highest possible that is less than
- the parameter value + 1. In practise this means that 62 is the only sensible
- value.
- Examples:
- 250MHz/4 = 62.5MHz (sdio_overclock=62)
- 250MHz/2 = 125MHz (sdio_overclock=125) # Too fast
- ---
- arch/arm/boot/dts/overlays/README | 9 ++++++---
- arch/arm/boot/dts/overlays/sdio-overlay.dts | 2 ++
- 2 files changed, 8 insertions(+), 3 deletions(-)
- --- a/arch/arm/boot/dts/overlays/README
- +++ b/arch/arm/boot/dts/overlays/README
- @@ -53,8 +53,8 @@ have its contents deleted (or commented
- Using Overlays
- ==============
-
- -Overlays are loaded using the "dtoverlay" directive. As an example, consider the
- -popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
- +Overlays are loaded using the "dtoverlay" directive. As an example, consider
- +the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
- pre-DT world this would be loaded from /etc/modules, with an explicit
- "modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
- this becomes a line in config.txt:
- @@ -621,9 +621,12 @@ Name: sdio
- Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
- and enables SDIO via GPIOs 22-27.
- Load: dtoverlay=sdio,<param>=<val>
- -Params: overclock_50 Clock (in MHz) to use when the MMC framework
- +Params: overclock_50 SD Clock (in MHz) to use when the MMC framework
- requests 50MHz
-
- + sdio_overclock SDIO Clock (in MHz) to use when the MMC
- + framework requests 50MHz
- +
- force_pio Disable DMA support (default off)
-
- pio_limit Number of blocks above which to use DMA
- --- a/arch/arm/boot/dts/overlays/sdio-overlay.dts
- +++ b/arch/arm/boot/dts/overlays/sdio-overlay.dts
- @@ -12,6 +12,7 @@
- pinctrl-0 = <&sdio_pins>;
- non-removable;
- bus-width = <4>;
- + brcm,overclock-50 = <0>;
- status = "okay";
- };
- };
- @@ -30,5 +31,6 @@
- __overrides__ {
- poll_once = <&sdio_mmc>,"non-removable?";
- bus_width = <&sdio_mmc>,"bus-width:0";
- + sdio_overclock = <&sdio_mmc>,"brcm,overclock-50:0";
- };
- };
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