Date:   Sun, 8 Apr 2018 08:23:53 +0000
From:   "liwei (CM)" <liwei213@...wei.com>
To:     Shawn Lin <shawn.lin@...k-chips.com>,
        Ryan Grachek <ryan@...ted.us>,
        "Jinguojun (A)" <kid.jin@...ilicon.com>,
        "jingbing (C)" <jingbing2@...ilicon.com>
CC:     Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Suzhuangluan <suzhuangluan@...ilicon.com>
Subject: 答复: [PATCH] mmc: dw_mmc-k3: Fix DDR52 mode by setting required clock divisor

+jinguojun jingbing

-----邮件原件-----
发件人: Shawn Lin [mailto:shawn.lin@...k-chips.com] 
发送时间: 2018年4月8日 9:52
收件人: Ryan Grachek
抄送: shawn.lin@...k-chips.com; Jaehoon Chung; Ulf Hansson; linux-mmc@...r.kernel.org; linux-kernel@...r.kernel.org; Zhangfei Gao; liwei (CM); Suzhuangluan
主题: Re: [PATCH] mmc: dw_mmc-k3: Fix DDR52 mode by setting required clock divisor

On 2018/4/6 21:41, Ryan Grachek wrote:
> On Wed, Apr 4, 2018 at 7:51 PM, Shawn Lin <shawn.lin@...k-chips.com> wrote:
>> [+ Zhangfei Gao who added support for hi6220]
>>
>> On 2018/4/4 23:31, Ryan Grachek wrote:
>>>
>>> On Tue, Apr 3, 2018 at 6:31 AM, Shawn Lin <shawn.lin@...k-chips.com 
>>> <mailto:shawn.lin@...k-chips.com>> wrote:
>>>
>>>      On 2018/3/30 2:24, oscardagrach wrote:
>>>
>>>      Need at least one line commit body.
>>>
>>>          Signed-off-by: oscardagrach <ryan@...ted.us 
>>> <mailto:ryan@...ted.us>>
>>>
>>>          ---
>>>             drivers/mmc/host/dw_mmc-k3.c | 10 ++++++++--
>>>             1 file changed, 8 insertions(+), 2 deletions(-)
>>>
>>>          diff --git a/drivers/mmc/host/dw_mmc-k3.c
>>>          b/drivers/mmc/host/dw_mmc-k3.c
>>>          index 89cdb3d533bb..efc546cb4db8 100644
>>>          --- a/drivers/mmc/host/dw_mmc-k3.c
>>>          +++ b/drivers/mmc/host/dw_mmc-k3.c
>>>          @@ -194,8 +194,14 @@ static void dw_mci_hi6220_set_ios(struct
>>>          dw_mci *host, struct mmc_ios *ios)
>>>                   int ret;
>>>                   unsigned int clock;
>>>             -     clock = (ios->clock <= 25000000) ? 25000000 : ios->clock;
>>>          -
>>>          +       /* CLKDIV must be 1 for DDR52/8-bit mode */
>>>          +       if (ios->bus_width == MMC_BUS_WIDTH_8 &&
>>>          +               ios->timing == MMC_TIMING_MMC_DDR52) {
>>>          +               mci_writel(host, CLKDIV, 0x1);
>>>          +               clock = ios->clock;
>>>          +       } else {
>>>          +               clock = (ios->clock <= 25000000) ? 25000000 :
>>>          ios->clock;
>>>          +       }
>>>
>>>
>>>      I undertand DDR52/8-bit need CLKDIV fixed 1, but shouldn't the 
>>> following
>>>      change is more sensible?
>>>
>>>      if (ios->bus_width == MMC_BUS_WIDTH_8 && ios->timing ==
>>>      MMC_TIMING_MMC_DDR52)
>>>               clock = ios->clock * 2;
>>>      else
>>>               clock = (ios->clock <= 25000000) ? 25000000 : 
>>> ios->clock;
>>>
>>>
>>>      The reason is ios->clock is 52MHz and you could claim 104MHz from the
>>>      clock provider and let dw_mmc core take care of the divder to be 1.
>>>      Otherwise, you just force it to be DDR52/8-bit with a clk rate 
>>> of 26MHz.
>>>
>>>
>>>                   ret = clk_set_rate(host->biu_clk, clock);
>>>                   if (ret)
>>>                           dev_warn(host->dev, "failed to set rate
>>>          %uHz\n", clock);
>>>
>>>
>>>
>>
>> For future wise, please use plain mode mail, but not HTML format.
>>
>>> Your feedback is correct. I see the Rockchip dwmmc driver has a 
>>> similar implementation. After applying your suggested changes, 
>>> however, my board reports "dwmmc_k3 f723d000.dwmmc0: failed to set rate 104000000Hz"
>>> during intialization of eMMC. In addition, I do not see CLKDIV being 
>>> set to 1. clk_set_rate fails and I wonder if this is out-of-scope of 
>>> the driver.
>>>
>>> If I set CLKDIV where I did prior, with your changes, the device 
>>> fails to set the clock and falls back to 52 MHz (26 MHz) and works 
>>> fine, but again, CLKDIV is reported as 0 (even though it is 1.) One 
>>> thing of interest to note is when I manually set the clock by doing:
>>> (echo 104000000 > /sys/kernel/debug/mmc0/clock) the device reports 
>>> back 'mmc_host mmc0: Bus speed (slot 0) = 198400000Hz (slot req 104000000Hz,
>>>    actual 99200000HZ div = 1)' which works reliably and clk_set_rate 
>>> does not report any error.
>>>
>>
>> When looking closely into the code, at least dw_mci_hi6220_set_ios 
>> goes wrong with the bus_hz, since it should be ciu_clk but not biu_clk.
>> "b" stands for bus, and "c" stands for card IMHO, however bus_hz 
>> describs the clock to the card, provided by controller. Does the 
>> following patch help?
>>
>>
>> diff --git a/drivers/mmc/host/dw_mmc-k3.c 
>> b/drivers/mmc/host/dw_mmc-k3.c index 89cdb3d..9e78cf2 100644
>> --- a/drivers/mmc/host/dw_mmc-k3.c
>> +++ b/drivers/mmc/host/dw_mmc-k3.c
>> @@ -194,13 +194,21 @@ static void dw_mci_hi6220_set_ios(struct dw_mci 
>> *host, struct mmc_ios *ios)
>>          int ret;
>>          unsigned int clock;
>>
>> -       clock = (ios->clock <= 25000000) ? 25000000 : ios->clock;
>> +       if (ios->bus_width == MMC_BUS_WIDTH_8 &&
>> +           ios->timing == MMC_TIMING_MMC_DDR52)
>> +               clock = ios->clock * 2;
>> +       else
>> +               clock = (ios->clock <= 25000000) ? 25000000 : 
>> + ios->clock;
>>
>> -       ret = clk_set_rate(host->biu_clk, clock);
>> +       ret = clk_set_rate(host->ciu_clk, clock);
>>          if (ret)
>>                  dev_warn(host->dev, "failed to set rate %uHz\n", 
>> clock);
>>
>> -       host->bus_hz = clk_get_rate(host->biu_clk);
>> +       clock = clk_get_rate(host->ciu_clk);
>> +       if (clock != host->bus_hz) {
>> +               host->bus_hz = clock;
>> +               host->current_speed = 0;
>> +       }
>>
>>   }
>>
>>
>>> I am not sure where to begin debugging these clock issues and 
>>> welcome any feedback.
>>
>>
> 
> The change results in the following:
> 'dwmmc_k3 f723e000.dwmmc1: failed to set rate 25000000Hz'
> 'dwmmc_k3 f723d000.dwmmc0: failed to set rate 25000000Hz'
> 'dwmmc_k3 f723f000.dwmmc2: failed to set rate 25000000Hz'
> 
> and later on:
> 'dwmmc_k3 f723d000.dwmmc0: failed to set rate 52000000Hz'
> 'dwmmc_k3 f723d000.dwmmc0: failed to set rate 104000000Hz'
> 
> Eventually mmc1 (UHS-1 MicroSD) will settle down after repeated 
> attempts at setting 25 MHz:
> 'mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 
> 100000000Hz, actual 100000000HZ div = 0)'
> 'mmc1: new ultra high speed SDR50 SDHC card at address 0001'
> 'mmcblk1: mmc1:0001 GB1QT 29.8 GiB'
> 
> Same for mmc2 (SDIO WL1835MOD WiFi):
> 'mmc_host mmc2: Bus speed (slot 0) = 100000000Hz (slot req 50000000Hz, 
> actual 50000000HZ div = 1)'
> 'mmc2: new high speed SDIO card at address 0001'
> 
> So mmc1 and mmc2 will initialize eventually. I had not observed this 
> behavior prior. It appears to fail setting all devices to an initial 
> rate of 25 MHz. However, the same cannot be said for mmc0 (eMMC).
> Again, I observed being able to set the clock manually through debugfs 
> to 104MHz(/2) which is successful and the card becomes stable and will 
> initialize properly.
> 
> 'echo 104000000 > /sys/kernel/debug/mmc0/clock'
> 'mmc_host mmc0: Bus speed (slot 0) = 200000000Hz (slot req 
> 104000000Hz, actual 100000000HZ div = 1)'
> 
> So it seems to settle down at 50 MHz, but only if set manually. It 
> does appear CLKDIV is being set accordingly now.

Hmm.... I can't see any differences.. And failed to set clock rate in the first place and finally got it, which beyond the mmc driver scope. Maybe hisilicon guys have more idea here.

> 
> 
> 

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