linux-kernel - Re: [PATCH V2 2/4] ARM64 LPC: LPC driver implementation on Hip06

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Date:   Tue, 13 Sep 2016 14:31:13 +0800
From:   zhichang <zhichang.yuan02@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        "zhichang.yuan" <yuanzhichang@...ilicon.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linuxarm@...wei.com,
        linux-kernel@...r.kernel.org, lorenzo.pieralisi@....com,
        minyard@....org, benh@...nel.crashing.org,
        gabriele.paoloni@...wei.com, john.garry@...wei.com,
        liviu.dudau@....com, zourongrong@...il.com
Subject: Re: [PATCH V2 2/4] ARM64 LPC: LPC driver implementation on Hip06



On 2016年09月08日 18:00, Arnd Bergmann wrote:
> On Thursday, September 8, 2016 4:06:01 PM CEST zhichang.yuan wrote:
>>>
>>>> +struct lpc_io_ops {
>>>> +    unsigned int periosz;
>>>> +    int (*lpc_iord)(struct hisilpc_dev *pdev, struct lpc_cycle_para *para,
>>>> +                            unsigned long ptaddr, unsigned char *buf,
>>>> +                            unsigned long dlen);
>>>> +    int (*lpc_iowr)(struct hisilpc_dev *pdev, struct lpc_cycle_para *para,
>>>> +                            unsigned long ptaddr,
>>>> +                            const unsigned char *buf,
>>>> +                            unsigned long dlen);
>>>> +};
>>>
>>> The operations are not needed unless we also put the earlycon support
>>> in, so maybe leave them out from the first patch and only add them
>>> later (or drop the earlycon support if possible).
>>
>> Do you want to remove the struct lpc_io_ops member from struct hisilpc_dev??
>> I think we can not do that.
>>
>> These two functions are essential rd/wr operation for Hip06 LPC. They will be fallen into
>> when the upper layer drivers call their own IO in/out functions, such as serial_in/serial_out
>> for 8250 serial.
>>
>> I can define lpc_iord/lpc_iowr directly in struct hisilpc_dev and cancel the definition of
>> struct lpc_io_ops. In my original idea, several LPC cycle types will be supported. Each cycle
>> type has its specific ops. Now, only one cycle type is needed, the struct lpc_io_ops is not
>> meaningful.
> 
> My point was that the indirect function calls are not needed at
> until patch four, so you can call the functions directly here,
> and make the logic for indirect function calls part of that
> later patch.
O. I think I got your meaning now.
In patch V2, the lpc_io_ops is not needed even if earlycon is supported. The early_in/early_out operation is
defined in hisi_lpc.c too, we can directly call the hisilpc_target_in/hisilpc_target_out to finish the LPC IO
operations.
At this moment, all the IO functions specific to the child devices of hip06 LPC have their own indirect call
method. This lpc_io_ops will be removed in V3.

> 
> What are the other LPC cycle types that could be supported?
O. memory and firmware operations are supported too. But at this moment, we only use IO cycle.

Best,
Zhichang

> 
> 	Arnd
>