From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Alexander Kurz <akurz@blala.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH 0/2] spi: imx: don't loop endlessly
Date: Mon, 2 Oct 2017 07:31:23 +0200 [thread overview]
Message-ID: <20171002053123.tphz7c44xofordvk@pengutronix.de> (raw)
In-Reply-To: <alpine.DEB.2.00.1709291955001.32464@blala.de>
On Fri, Sep 29, 2017 at 08:08:28PM +0200, Alexander Kurz wrote:
> Hi,
> during xchg_single 32 bits will be sent and received:
> 2x32 bits / 10 Microseconds = 6.4MHz Clock.
why 2x?
> Hence, a 10 Microseconds timeout will break SPI communication for
> boards with SPI frequencies less then 6.4MHz.
> On some boards spi-max-frequency is limited due to improper communication
> at higher frequencies, e.g. for the kindle4 it is 1MHz and there
> also exists one board with 100kHz.
>
> Before sending a patch calculating the timeout from spi-max-frequency,
> is 640 Microseconds (to fit imx28-cfa10049.dts 100kHz) acceptable?
I would expect that the hardware and software add some latency, so maybe
round it up to 1 ms?
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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prev parent reply other threads:[~2017-10-02 5:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 19:39 Uwe Kleine-König
2017-08-02 19:39 ` [PATCH 1/2] spi: imx: add error checking Uwe Kleine-König
2017-08-02 19:39 ` [PATCH 2/2] spi: imx: add timeout to xchg_single Uwe Kleine-König
2017-08-02 19:54 ` [PATCH 0/2] spi: imx: don't loop endlessly Sam Ravnborg
2017-08-02 20:19 ` Uwe Kleine-König
2017-08-02 20:32 ` Sam Ravnborg
2017-08-03 9:07 ` Uwe Kleine-König
2017-08-03 10:43 ` Sam Ravnborg
2017-08-03 18:41 ` Uwe Kleine-König
2017-09-29 18:08 ` Alexander Kurz
2017-10-02 5:31 ` Uwe Kleine-König [this message]
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