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From 94dab6838e9ba91d6da49d864b0f408a89f08ce5 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 25 Jan 2016 09:12:06 +0000
Subject: [PATCH 138/156] 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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