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authorMugunthan V N <mugunthanvnm@ti.com>2016-03-07 01:41:22 -0700
committerPaul Walmsley <paul@pwsan.com>2016-03-07 01:41:22 -0700
commit0f514e690740e54815441a87708c3326f8aa8709 (patch)
treea1159d2060045fc2fa1d1300b59420137055c701
parent2e18f5a1bc18e8af7031b3b26efde25307014837 (diff)
ARM: dts: dra7: do not gate cpsw clock due to errata i877
Errata id: i877 Description: ------------ The RGMII 1000 Mbps Transmit timing is based on the output clock (rgmiin_txc) being driven relative to the rising edge of an internal clock and the output control/data (rgmiin_txctl/txd) being driven relative to the falling edge of an internal clock source. If the internal clock source is allowed to be static low (i.e., disabled) for an extended period of time then when the clock is actually enabled the timing delta between the rising edge and falling edge can change over the lifetime of the device. This can result in the device switching characteristics degrading over time, and eventually failing to meet the Data Manual Delay Time/Skew specs. To maintain RGMII 1000 Mbps IO Timings, SW should minimize the duration that the Ethernet internal clock source is disabled. Note that the device reset state for the Ethernet clock is "disabled". Other RGMII modes (10 Mbps, 100Mbps) are not affected Workaround: ----------- If the SoC Ethernet interface(s) are used in RGMII mode at 1000 Mbps, SW should minimize the time the Ethernet internal clock source is disabled to a maximum of 200 hours in a device life cycle. This is done by enabling the clock as early as possible in IPL (QNX) or SPL/u-boot (Linux/Android) by setting the register CM_GMAC_CLKSTCTRL[1:0]CLKTRCTRL = 0x2:SW_WKUP. So, do not allow to gate the cpsw clocks using ti,no-idle property in cpsw node assuming 1000 Mbps is being used all the time. If someone does not need 1000 Mbps and wants to gate clocks to cpsw, this property needs to be deleted in their respective board files. Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com> Cc: <stable@vger.kernel.org> Signed-off-by: Paul Walmsley <paul@pwsan.com>
-rw-r--r--arch/arm/boot/dts/dra7.dtsi10
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi
index c4d9175b90dc..f82aa44c3cee 100644
--- a/arch/arm/boot/dts/dra7.dtsi
+++ b/arch/arm/boot/dts/dra7.dtsi
@@ -1500,6 +1500,16 @@
0x48485200 0x2E00>;
#address-cells = <1>;
#size-cells = <1>;
+
+ /*
+ * Do not allow gating of cpsw clock as workaround
+ * for errata i877. Keeping internal clock disabled
+ * causes the device switching characteristics
+ * to degrade over time and eventually fail to meet
+ * the data manual delay time/skew specs.
+ */
+ ti,no-idle;
+
/*
* rx_thresh_pend
* rx_pend