Re: [PATCH 3/3] ARM: dts: exynos5422-odroidxu3: Added UHS-I bus speed support

[Anand Moon <linux.amoon@gmail.com>]

Hi Krzysztof,

On 13 October 2015 at 09:13, Krzysztof Kozlowski
<k.kozlowski@samsung.com> wrote:
>
> On 13.10.2015 12:08, Anand Moon wrote:
> > Hi Krzysztof,
> >
> > On 13 October 2015 at 05:44, Krzysztof Kozlowski
> > <k.kozlowski@samsung.com> wrote:
> >> On 13.10.2015 00:32, Anand Moon wrote:
> >>> Hi Krzysztof,
> >>>
> >>> On 12 October 2015 at 11:14, Krzysztof Kozlowski
> >>> <k.kozlowski@samsung.com> wrote:
> >>>> On 12.10.2015 00:46, Anand Moon wrote:
> >>>>> Added support for UHS-I bus speed 50MB/s (SDR50, DDR50) 104MB/s (SDR104)
> >>>>
> >>>> This description is not entirely correct. The MMC driver already
> >>>> supports these UHS speeds (you did not any code) so you rather enabled
> >>>> it (description of bindings says "is supported").
> >>>>
> >>>> You mentioned DDR50 but I don't see respective property below.
> >>>>
> >>>> How do you know that these modes are really supported? I don't know. Can
> >>>> you convince me?
> >>>
> >>> Setting this DDR50 capability give me this error. That's the reason to
> >>> drop this capability.
> >>
> >> But you mentioned it in commit message! "Added support for UHS-I ...
> >> (DDR50)"
> >>
> >> In the same time dropping DDR50 is not an sufficient proof that "SDR50
> >> and SDR104 are really supported".
> >>
> >
> > These changes are related to the microSD card capabilities.
> > So SDR50 have better frequency over DDR50. On the same Sandisk card.
> >
> > When the card select the capability for DDR50
> > ---------------------------------------------------
> > [    4.001477] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot
> > req 50000000Hz, actual 50000000HZ div = 0)
> > [    4.001604] mmc1: new ultra high speed DDR50 SDHC card at address aaaa
> > [    4.004505] mmcblk0: mmc1:aaaa SL32G 29.7 GiB
> > [    4.009179] mmcblk0: error -110 sending status command, retrying
> > [    4.009271] mmcblk0: error -115 sending stop command, original cmd
> > response 0x900, card status 0x900
> > [    4.009275] mmcblk0: error -84 transferring data, sector 0, nr 8,
> > cmd response 0x900, card status 0x0
> > [    4.025563] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot
> > req 400000Hz, actual 396825HZ div = 63)
> > [    4.067770] Console: switching to colour frame buffer device 274x77
> > [    4.098782] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot
> > req 50000000Hz, actual 50000000HZ div = 0)
> > [    4.099692] mmc1: tried to reset card
> > [    4.101332]  mmcblk0: p1 p2
> >
> >
> > When the card select the capability for SDR50
> > ---------------------------------------------------------------------------------
> > [ 2.439806] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req
> > 100000000Hz, actual 100000000HZ div = 0)
> > [ 2.449729] mmc1: new ultra high speed SDR50 SDHC card at address aaaa
> > [ 2.455984] mmcblk0: mmc1:aaaa SL32G 29.7 GiB
> > [ 2.461743] mmcblk0: p1 p2
> >
> > Which will relate to better read/write speed.
>
> Which is not an answer to my question. To none of my previous questions.
>

Basically UHS-I capability  (sd-uhs-sdr12, sd-uhs-sdr25, sd-uhs-sdr50,
sd-uhs-sdr104) help tune speed supported for mmc

I have tired to compare the speed on high speed UHS-I vs ultra high
speed UHS-I using izone utility.

[    2.572469] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot
req 50000000Hz, actual 50000000HZ div = 0)
[    2.572609] mmc1: new high speed SDHC card at address aaaa

      Command line used: ./iozone -L64 -S32 -azecwI -+n -r4k -r64k
-r128k -s10M -i0 -i1 -i2 -f datafile -Rb out.xls
        Output is in kBytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 32 kBytes.
        Processor cache line size set to 64 bytes.
        File stride size set to 17 * record size.
                                                              random
 random     bkwd    record    stride
              kB  reclen    write  rewrite    read    reread    read
  write     read   rewrite      read   fwrite frewrite    fread
freread
           10240       4     1631        0     6556        0     5538      982
           10240      64     8828        0    18897        0    17994      303
           10240     128     6269        0    20670        0    20128     1096
---------------------------------------------------------------------------------------------------------
[    2.613761] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot
req 100000000Hz, actual 100000000HZ div = 0)
[    2.623573] mmc1: new ultra high speed SDR50 SDHC card at address aaaa

        Command line used: ./iozone -L64 -S32 -azecwI -+n -r4k -r64k
-r128k -s10M -i0 -i1 -i2 -f datafile -Rb out.xls
        Output is in kBytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 32 kBytes.
        Processor cache line size set to 64 bytes.
        File stride size set to 17 * record size.
                                                              random
 random     bkwd    record    stride
              kB  reclen    write  rewrite    read    reread    read
  write     read   rewrite      read   fwrite frewrite    fread
freread
           10240       4     1809        0     7507        0     5233      859
           10240      64    11622        0    31250        0    28072      516
           10240     128     4320        0    34417        0    32509     1148

My observation is that their slight increase in read/write operation.

Hope I have tried to answer you query. If I am wrong please let me know.

-Anand Moon

>
> Best regards,
> Krzysztof