From: <ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
To: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
Cc: nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org,
plagnioj-sclMFOaUSTBWk0Htik3J/w@public.gmane.org,
n.voss-+umVssTZoCsb1SvskN2V4Q@public.gmane.org,
w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org,
Ludovic Desroches
<ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
Subject: [PATCH v2 2/8] i2c: at91: add warning about transmission issues for some devices
Date: Mon, 3 Sep 2012 12:16:01 +0200 [thread overview]
Message-ID: <1346667367-7969-3-git-send-email-ludovic.desroches@atmel.com> (raw)
In-Reply-To: <1346667367-7969-1-git-send-email-ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
From: Ludovic Desroches <ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
Some devices don't have clock streching in transmission mode. It can
lead to premature stop sendings if the latency to write data in the
transmission register is too long. In this case, prefer the i2c-gpio
driver.
Signed-off-by: Ludovic Desroches <ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
Acked-by: Nikolaus Voss <n.voss-+umVssTZoCsb1SvskN2V4Q@public.gmane.org>
Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
drivers/i2c/busses/Kconfig | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index d9c4918..da77c37 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -300,6 +300,12 @@ config I2C_AT91
to support combined I2C messages. Use the i2c-gpio driver
unless your system can cope with this limitation.
+ Caution! at91rm9200, at91sam9261, at91sam9260, at91sam9263 devices
+ don't have clock stretching in transmission mode. For that reason,
+ you can encounter underrun issues causing premature stop sendings if
+ the latency to fill the transmission register is too long. If you
+ are facing this situation, use the i2c-gpio driver.
+
config I2C_AU1550
tristate "Au1550/Au1200/Au1300 SMBus interface"
depends on MIPS_ALCHEMY
--
1.7.11.3
next prev parent reply other threads:[~2012-09-03 10:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-03 10:15 [PATCH v2 0/8] i2c: at91: cleanup and dt support ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
[not found] ` <1346667367-7969-1-git-send-email-ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
2012-09-03 10:16 ` [PATCH v2 1/8] i2c: at91: use managed resources ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:16 ` ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w [this message]
2012-09-03 10:16 ` [PATCH v2 3/8] i2c: at91: use an id table for SoC dependent parameters ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:16 ` [PATCH v2 4/8] ARM: at91: do not configure at91sam9g10 twi pio as open-drain ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:18 ` [PATCH v2 5/8] i2c: at91: add dt support to i2c-at91 ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:19 ` [PATCH v2 6/8] ARM: at91: add clocks for I2C DT entries ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:19 ` [PATCH v2 7/8] ARM: dts: add twi nodes for atmel SoCs ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
2012-09-03 10:20 ` [PATCH v2 8/8] ARM: dts: add twi nodes for atmel boards ludovic.desroches-AIFe0yeh4nAAvxtiuMwx3w
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