Re: MCAN Registers Discrepancy

From: "Mario Hüttel" <mario.huettel@gmx.net>
To: Franklin S Cooper Jr <fcooper@ti.com>,
	linux-can@vger.kernel.org, wg@grandegger.com, mkl@pengutronix.de,
	b29396@freescale.com, socketcan@hartkopp.net
Subject: Re: MCAN Registers Discrepancy
Date: Thu, 29 Jun 2017 16:52:51 +0200	[thread overview]
Message-ID: <b640c93b-23fe-82dc-b0ec-5c77fea64ed7@gmx.net> (raw)
In-Reply-To: <62a65051-a8f4-0bd9-238c-0e28814e4249@ti.com>

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Hello,

you are right. There are/were some incosistencies in the values.

However, the driver used them correctly. The driver version you

talk about is not entirely compatible with the user manual you provided.

I wrote some patches back in April which add support for the newer M_CAN

versions up to 3.2.X:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/drivers/net/can/m_can

These should work as intended.

Before, the driver could only handle IP versions 3.0.X.

Mario

On 06/28/2017 11:49 PM, Franklin S Cooper Jr wrote:
> Hi,
>
> When looking at the latest versions of the MCAN user manual it seems
> that there is a discrepancy between the various BTR_XX_MASK and
> BTR_XX_SHIFT values. For example BTR_TSEG2_MASK is set to 0xF and
> BTR_TSEG2_SHIFT is 4. However, based on page 21 of the latest version of
> the MCAN User Manual NTSEG2 starts at bit 0. Therefore, it should have a
> shift value of 0. Also it is a 7 bit field so its mask should be 0x7F. I
> see similar issues with FBTR_XXX_MASK values.
>
> So the original driver mentioned it was based on rev version 3.1.0 of
> the User Manual while the latest version publicly available is 3.2.12.
> Since I don't see any current users of this driver in upstream I am
> unsure if this is just a bug in the code or if the current values are
> correct for older versions of the IP.
>
> Does anyone have a copy of this older document available that they can
> share? Or at the very least verify that the current values were correct
> in older revisions of the MCAN IP? I need to make updates to the drivers
> but I want to avoid breaking things for other people.
>
> Latest version of the MCAN User Manual can be found at:
> http://www.bosch-semiconductors.de/media/automotive_electronics/pdf_2/ipmodules_3/m_can_m_ttcan_1/mcan_users_manual_v3212.pdf
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