linux-kernel - Re: [PATCH 2/2] can: tcan4x5x: Add tcan4x5x driver to the kernel

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Date:   Fri, 5 Oct 2018 06:45:38 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Wolfgang Grandegger <wg@...ndegger.com>, <mkl@...gutronix.de>,
        <davem@...emloft.net>
CC:     <linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        "Mario.Huettel" <Mario.Huettel@...bosch.com>
Subject: Re: [PATCH 2/2] can: tcan4x5x: Add tcan4x5x driver to the kernel

Wolfgang

On 10/05/2018 12:56 AM, Wolfgang Grandegger wrote:
> Hello Dan,
> 
> Am 04.10.2018 um 22:26 schrieb Dan Murphy:
>> Wolfgang
>>
>> On 09/26/2018 12:54 PM, Wolfgang Grandegger wrote:
>>> Hello,
>>>
>>> I wonder why you do not extend the existing MCAN driver by implementing
>>> an interface to access the hardware. Would that be feasible?
>>>
>>
>> I have created a m_can_core code base that can be used by other hardware that
>> have special needs.
>>
>> So I have created the m_can_core, m_can and the tcan4x5x drivers.
> 
> Great, I still think it's a good idea to have just one "m_can" driver.

The m_can and tcan4x5x provide the device level implementations.  The m_can_core
deals specifically with handling of the m_can IP and protocol.

> 
>> I can RFC the code to see if this is what is expected.
>> It is not 100% working but it is close enough for a directional call.
> 
> That would be nice! Most of the SPI accesses are pure register accesses.
> A few read/write more bytes at a time (for data, etc.) but that could be
> handled by appropriate interface functions. One general problem is that
> SPI accesses are not possible from interrupt context requiring threads
> or work queues. Also NAPI is usually not used.
> 
> Other opinions?

agreed. Is there any issue with moving the request_irq to a threaded_irq?
Not sure how that would affect the timing.

> 
> Wolfgang.
> 
> PS: I have added Mario to the CC. Maybe he could test a common driver on
> his M_CAN hardware.
> 

I found that our am5/dra76 EVM also uses this IP stack.  So I am working with
our experts there to test and review the code as well.

Dan

-- 
------------------
Dan Murphy