linux-kernel - Re: [PATCH RESEND v10 3/4] PHY: add APM X-Gene SoC 15Gbps Multi-purpose PHY driver

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Date:	Thu, 27 Feb 2014 12:17:20 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Loc Ho <lho@....com>
CC:	Tejun Heo <tj@...nel.org>, Olof Johansson <olof@...om.net>,
	Arnd Bergmann <arnd@...db.de>, <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Don Dutile <ddutile@...hat.com>, Jon Masters <jcm@...hat.com>,
	"patches@....com" <patches@....com>, Tuan Phan <tphan@....com>,
	Suman Tripathi <stripathi@....com>
Subject: Re: [PATCH RESEND v10 3/4] PHY: add APM X-Gene SoC 15Gbps Multi-purpose
 PHY driver

On Thursday 27 February 2014 12:11 PM, Loc Ho wrote:
> Hi,
>
>>>>>>> +
>>>>>>> +static void sds_wr(void __iomem *csr_base, u32 indirect_cmd_reg,
>>>>>>> +                  u32 indirect_data_reg, u32 addr, u32 data)
>>>>>>> +{
>>>>>>> +       u32 val;
>>>>>>> +       u32 cmd;
>>>>>>> +
>>>>>>> +       cmd = CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK;
>>>>>>> +       cmd = CFG_IND_ADDR_SET(cmd, addr);
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> This looks hacky. If 'CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK'
>>>>>> should
>>>>>> be set then it should be part of the second argument. From the macro
>>>>>> 'CFG_IND_ADDR_SET' the first argument should be more like the current
>>>>>> value
>>>>>> present in the register right? I feel the macro (CFG_IND_ADDR_SET) is
>>>>>> not
>>>>>> used in the way it is intended to.
>>>>>
>>>>>
>>>>>
>>>>> The macro XXX_SET is intended to update an field within the register.
>>>>> The update field is returned. The first assignment lines are setting
>>>>> another field. Those two lines can be written as:
>>>>>
>>>>> cmd = 0;
>>>>> cmd |= CFG_IND_WR_CMD_MASK;            ==> Set the CMD bit
>>>>> cmd |= CFG_IND_CMD_DONE_MASK;        ==> Set the DONE bit
>>>>> cmd = CFG_IND_ADDR_SET(cmd, addr);    ===> Set the field ADDR
>>>>
>>>>
>>>>
>>>> #define  CFG_IND_ADDR_SET(dst, src) \
>>>>                   (((dst) & ~0x003ffff0) | (((u32)(src)<<4) & 0x003ffff0))
>>>>
>>>>   From this macro the first argument should be the present value in that
>>>> register. Here you reset the address bits and write the new address bits.
>>>
>>>
>>> Yes.. This is correct. I am clearing x number of bit and then set new
>>> value.
>>>
>>>> IMO the first argument should be the value in 'csr_base +
>>>> indirect_cmd_reg'.
>>>> So it resets the address bits in 'csr_base + indirect_cmd_reg' and write
>>>> down the new address bits.
>>>
>>>
>>> Yes.. The above code does just that. In addition, I am also setting
>>> the bits CFG_IND_WR_CMD_MASK and CFG_IND_CMD_DONE_MASK with the two
>>> previous statement. Think of the code flow as follow:
>>>
>>> val = readl(some void * address); /* read the register */
>>
>>
>> Where are you reading the register in your code (before CFG_IND_ADDR_SET)?
>
> I am not reading the register as I will be completely setting them.

Ok. Never-mind then. Sorry for the noise. You code is fine.

Thanks
Kishon
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