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70 lines
2.8 KiB
Diff
70 lines
2.8 KiB
Diff
From 9a7e2ae47f11f7ff5cb4dd2b87e9caeb0953b18d Mon Sep 17 00:00:00 2001
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From: Phil Elwell <phil@raspberrypi.org>
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Date: Mon, 25 Jan 2016 09:12:06 +0000
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Subject: [PATCH 136/304] BCM270X_DT: Add sdio_overclock parameter to sdio
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overlay
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The sdio_overclock parameter is like the overclock_50 parameter, i.e.
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it sets an alternate frequency (in MHz) to use when the MMC framework
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requests 50MHz, except that it applies to the SDIO bus.
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Be aware that the actual frequencies achievable are limited to even integer
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divisions of 250MHz, and that the driver will round up to include fractions
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(e.g. 62 will include 62.5) but then round down to the nearest frequency.
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In other words, the chosen frequency is the highest possible that is less than
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the parameter value + 1. In practise this means that 62 is the only sensible
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value.
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Examples:
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250MHz/4 = 62.5MHz (sdio_overclock=62)
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250MHz/2 = 125MHz (sdio_overclock=125) # Too fast
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---
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arch/arm/boot/dts/overlays/README | 9 ++++++---
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arch/arm/boot/dts/overlays/sdio-overlay.dts | 2 ++
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2 files changed, 8 insertions(+), 3 deletions(-)
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--- a/arch/arm/boot/dts/overlays/README
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+++ b/arch/arm/boot/dts/overlays/README
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@@ -53,8 +53,8 @@ have its contents deleted (or commented
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Using Overlays
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==============
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-Overlays are loaded using the "dtoverlay" directive. As an example, consider the
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-popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
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+Overlays are loaded using the "dtoverlay" directive. As an example, consider
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+the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
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pre-DT world this would be loaded from /etc/modules, with an explicit
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"modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
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this becomes a line in config.txt:
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@@ -621,9 +621,12 @@ Name: sdio
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Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
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and enables SDIO via GPIOs 22-27.
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Load: dtoverlay=sdio,<param>=<val>
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-Params: overclock_50 Clock (in MHz) to use when the MMC framework
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+Params: overclock_50 SD Clock (in MHz) to use when the MMC framework
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requests 50MHz
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+ sdio_overclock SDIO Clock (in MHz) to use when the MMC
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+ framework requests 50MHz
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+
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force_pio Disable DMA support (default off)
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pio_limit Number of blocks above which to use DMA
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--- a/arch/arm/boot/dts/overlays/sdio-overlay.dts
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+++ b/arch/arm/boot/dts/overlays/sdio-overlay.dts
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@@ -12,6 +12,7 @@
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pinctrl-0 = <&sdio_pins>;
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non-removable;
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bus-width = <4>;
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+ brcm,overclock-50 = <0>;
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status = "okay";
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};
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};
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@@ -30,5 +31,6 @@
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__overrides__ {
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poll_once = <&sdio_mmc>,"non-removable?";
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bus_width = <&sdio_mmc>,"bus-width:0";
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+ sdio_overclock = <&sdio_mmc>,"brcm,overclock-50:0";
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};
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};
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