linux-kernel - Re: [PATCH V14 1/2] scsi: ufs: set the device reference clock setting

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Message-ID: <0761c2c2-4366-0a20-6789-10c4c9498908@codeaurora.org>
Date:   Mon, 24 Sep 2018 14:17:54 +0530
From:   Sayali Lokhande <sayalil@...eaurora.org>
To:     Avri Altman <Avri.Altman@....com>,
        "subhashj@...eaurora.org" <subhashj@...eaurora.org>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "vivek.gautam@...eaurora.org" <vivek.gautam@...eaurora.org>,
        "rnayak@...eaurora.org" <rnayak@...eaurora.org>,
        "vinholikatti@...il.com" <vinholikatti@...il.com>,
        "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "evgreen@...omium.org" <evgreen@...omium.org>,
        "riteshh@...eaurora.org" <riteshh@...eaurora.org>
Cc:     "stummala@...eaurora.org" <stummala@...eaurora.org>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "jlbec@...lplan.org" <jlbec@...lplan.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V14 1/2] scsi: ufs: set the device reference clock setting


On 9/24/2018 1:28 PM, Avri Altman wrote:
>> +static struct ufs_ref_clk ufs_ref_clk_freqs[] = {
>> +       {19200000, REF_CLK_FREQ_19_2_MHZ},
>> +       {26000000, REF_CLK_FREQ_26_MHZ},
>> +       {38400000, REF_CLK_FREQ_38_4_MHZ},
>> +       {52000000, REF_CLK_FREQ_52_MHZ},
>> +       {0, REF_CLK_FREQ_INVAL},
>> +};
>> +
>> +static inline enum ufs_ref_clk_freq
>> +ufs_get_bref_clk_from_hz(u32 freq)
>> +{
>> +       int i = 0;
>> +
>> +       while (ufs_ref_clk_freqs[i].freq_hz != freq) {
>> +               if (!ufs_ref_clk_freqs[i].freq_hz)
>> +                       return REF_CLK_FREQ_INVAL;
> Is the if clause really needed?
> you will return REF_CLK_FREQ_INVAL anyway
Yes. the if condition makes sure to return REF_CLK_FREQ_INVAL if freq is 
not what we expect.
>
>> +               i++;
> You might overrun here if freq is not what you've expected
Above if condition "if (!ufs_ref_clk_freqs[i].freq_hz)" prevents such 
overrun
as we will reach end of ufs_ref_clk_freqs[] (i.e upto  0, 
REF_CLK_FREQ_INVAL) when there is no match and thus we will return 
REF_CLK_FREQ_INVAL.
>> +       }
>> +
>> +       return ufs_ref_clk_freqs[i].val;
>> +}