linux-kernel - Re: [PATCH 2/2] mmc: rtsx: modify phase searching method for tunning

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Date:	Wed, 20 Nov 2013 17:13:13 +0800
From:	micky <micky_ching@...lsil.com.cn>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	<cjb@...top.org>, <sameo@...ux.intel.com>,
	<gregkh@...uxfoundation.org>, <linux-mmc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <wei_wang@...lsil.com.cn>,
	<devel@...uxdriverproject.org>
Subject: Re: [PATCH 2/2] mmc: rtsx: modify phase searching method for tunning

Hi Dan:
On 11/20/2013 04:17 PM, Dan Carpenter wrote:
> On Tue, Nov 19, 2013 at 07:10:35PM +0800, micky_ching@...lsil.com.cn wrote:
>> -static u8 sd_search_final_phase(struct realtek_pci_sdmmc *host, u32 phase_map)
>> +static inline u32 sd_get_phase_point(u32 phase_map, unsigned int idx)
>>   {
>> -	struct timing_phase_path path[MAX_PHASE + 1];
>> -	int i, j, cont_path_cnt;
>> -	int new_block, max_len, final_path_idx;
>> -	u8 final_phase = 0xFF;
>> +	idx &= MAX_PHASE;
>> +	return phase_map & (1 << idx);
>> +}
>> +
> This function is confusing....
>
> MAX_PHASE is a terrible name.  It's in a global header but it doesn't
> have a prefix.  It should be #define RTS_MAX_PHASE.  It's weird that we
> are using it both as a number and as bit mask.  It's weird that we
> always add a "+ 1" to MAX_PHASE.  It means the name is chosen poorly.
> Maybe it should be:
>
> #define RTS_MAX_PHASE  32
> #define RTS_PHASE_MASK 0x1f
That's good, I will modify and resend.
> So this function takes a phase_map and an index and it wraps the index
> by masking away the top bits then it tests to see if the wrapped index
> bit is set?  The wrapping is very strange.
We use this function to find whether the bit of index in the phase_map
is 1. The index can be twice as MAX_PHASE(reach to 63), because we use
a unidirectional search, start search continuous phase to found the
max continuous length from 0, 1, ..., to 31. When we start from
bit31, index 32 should wrap as 0. This function can be replaced by mod
function(idx %= MAX_PHASE + 1).
> The name of the function is sd_get_phase_point() but we only test to
> see if it returns zero.  The name of the function is not helpful.
> "sd" is a generic prefix.
> "get" is misleading because we don't "get" anything it only returns zero
> on success?
> "phase_point" might be helpful but I don't know what a phase_point is.
> Add a comment about that maybe.
Yes, thank you for your suggestion, the function name is really not good.
I want use test_phase_bit(u32 phase_map, unsigned int bit), is that ok?
> regards,
> dan carpenter
>
> .
>


-- 
Best Regards
Micky.

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