linux-kernel - Re: [RFC 1/2] ARM: dts: exynos: update the usbdrd phy and ref clk

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Date:   Mon, 9 Oct 2017 02:36:13 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Kukjin Kim <kgene@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lee Jones <lee.jones@...aro.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 1/2] ARM: dts: exynos: update the usbdrd phy and ref clk

Hi Krzysztof,

On 8 October 2017 at 21:17, Krzysztof Kozlowski <krzk@...nel.org> wrote:
> On Sun, Oct 08, 2017 at 06:06:19PM +0530, Anand Moon wrote:
>> Hi Krzysztof,
>>
>> On 6 October 2017 at 12:08, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>> > On Fri, Oct 6, 2017 at 6:36 AM, Anand Moon <linux.amoon@...il.com> wrote:
>> >> update the usbdrd link control and phy contol clks.
>> >
>> > The commit title and especially commit message should explain why you
>> > are doing this and what are you doing. "Update" is not enough.
>> > Everything could be called update.
>> >
>> > Therefore I do not understand the reason behind the patch.
>> >
>> > BR,
>> > Krzysztof
>>
>> so as per the driver.
>> @clk: phy clock for register access
>> @ref_clk: reference clock to PHY block from which PHY's operational
>> clocks are derived
>>
>> Both CLK_SCLK_USBPHY300 and CLK_SCLK_USBD300 belong to FSYS Clock
>> and CLK_USBD300 clk is being used by the usbdrd dwc3 module.
>>
>> [0] https://github.com/torvalds/linux/blob/master/drivers/clk/samsung/clk-exynos5420.c#L1040-L1053
>>
>> So their is mismatch of the clk used by the usbdrd driver.
>
> Where is the mismatch? I do not understand.
>
>> with the above changes the driver work well with camera and disk drives
>> connected to usb 3.0 ports and their is improvement in the performance.
>
> If something is not working now, please describe it exactly so we could
> both reproduce and then observe the end results of fix.
>
> I do not understand how the change of these clocks brings improvement in
> performance... ok, sometimes it might happen if the rate of clock is
> being used on bus. Is this the case?
>
> Best regards,
> Krzysztof
>
[snip]

As per Exynos5422 CMU

CLK_SCLK_USBPHY300 and CLK_SCLK_USBD300 are special clk meant to
control the usbdrd

CLK_SCLK_USBPHY300/1 is used for phy control
CLK_SCLK_USBD300/1 is used for link control.

Following link share the details of the CMU_TOP
[0] https://imgur.com/9OKaXEM

On Odroid cloudshell module with old hard disk it time to time do reset of hub.
on heavy traffic of data.

[46953.765974] usb 4-1.1: reset SuperSpeed USB device number 3 using xhci-hcd
[47006.851310] usb 4-1.1: reset SuperSpeed USB device number 3 using xhci-hcd

[  730.078441] sd 1:0:0:0: [sdb] tag#5 CDB: opcode=0x2a 2a 00 26 b6 58
80 00 00 80 00
[  730.078471] sd 1:0:0:0: [sdb] tag#6 uas_zap_pending 0 uas-tag 7 inflight: CMD
[  730.078498] sd 1:0:0:0: [sdb] tag#6 CDB: opcode=0x28 28 00 00 00 20
00 00 04 00 00
[  730.161071] usb 4-1.2: reset SuperSpeed USB device number 4 using xhci-hcd
[  730.187194] scsi host1: uas_eh_bus_reset_handler success

At some time it work stable but eventfully their is loss of data.

On 3.10.x
It clk gate is tuned to support CLK_GATE_MULTI_BIT_SET, I am not sure
how this will apply on 4.x kernel

[1] https://github.com/hardkernel/linux/blob/odroidxu3-3.10.y/drivers/clk/samsung/clk-exynos5422.c#L1771-L1777

Best Regards
-Anand