From: John Watts <contact@jookia.org>
To: Sascha Hauer <sha@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] I2C: i.MX: early: Use internal udelay
Date: Mon, 30 Jan 2023 21:42:53 +1100 [thread overview]
Message-ID: <Y9efLdQi++e/ZFOn@novena-choice-citizen> (raw)
In-Reply-To: <20230130102727.GQ13319@pengutronix.de>
On Mon, Jan 30, 2023 at 11:27:27AM +0100, Sascha Hauer wrote:
> This takes around 5 times too long on a i.MX8MM and around 50 times too
> long on a i.MX6Q. This was measured under a regular barebox on the
> shell. In an early environment with MMU disabled it takes 730 times too
> long.
Yikes! I'm glad I broke this in to its own patch then. :)
I did copy this code from these boards:
arch/arm/boards/cm-fx6/lowlevel.c
arch/arm/boards/skov-imx6/lowlevel.c
arch/arm/boards/technexion-wandboard/lowlevel.c
arch/arm/mach-imx/xload-gpmi-nand.c
arch/arm/mach-imx/imx6-mmdc.c (uses 1000 loops)
Maybe it's time for an i.MX6-wide early udelay?
Though this code might break if its timing is already wrong.
> Maybe we could do this:
>
> static void __udelay(void *base, int us)
> {
> int i;
>
> for (i = 0; i < us * 4; i++)
> readb(base);
> }
>
> The time spent for a register read depends on the bus clock which
> doesn't change that much between the different SoCs.
This seems like a better solution if you've tested it, I'm not too sure
how to check this. Would I just then specify the controller as the base?
Though the actual goal of the code is to wait for the controller to bestable.
Maybe there's a better way than a delay?
>
> Sascha
John.
next prev parent reply other threads:[~2023-01-30 18:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-26 18:56 John Watts
2023-01-30 10:27 ` Sascha Hauer
2023-01-30 10:42 ` John Watts [this message]
2023-01-30 12:17 ` Sascha Hauer
2023-01-30 12:24 ` John Watts
2023-01-30 12:31 ` Sascha Hauer
2023-01-30 12:56 ` John Watts
2023-01-30 16:36 ` Sascha Hauer
2023-01-30 18:42 ` John Watts
2023-01-31 6:14 ` Sascha Hauer
2023-01-31 6:33 ` John Watts
2023-02-02 14:21 ` Jules Maselbas
2023-02-02 14:27 ` Ahmad Fatoum
2023-02-01 17:50 ` Alexander Shiyan
2023-02-01 18:12 ` Jookia
2023-02-01 19:44 ` Ahmad Fatoum
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