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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1570257

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
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This change has been made by an automated script, maintained by the
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** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1570257

Title:
  [Lenovo X220] SDXC UHS card slow performance

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Steps to reproduce:
   - Install ubuntu on Lenovo X220 laptop (checked with Linux Mint 17.3 (based on Ubuntu Trusty LTS) and LiveUSB of Ubuntu 15.10)
   - Insert and mount SDXC  UHS card.
   - Try to read some files from mounted card.

  Results:
   - Actual read speed is about 20 MB/s.
   - Expected speed is higher, because I checked the same card in the same laptop with external USB2.0 cardreader and it gives about 36MB/s and I think USB3.0 could give more.
   - Actually cardreader in X220 model connected via PCI-E bus, so the performance must be al least equal to USB reader, but it actually almost 2 times lower.

  Some details:
   - I supposed this bug is relevant to #773524 bug, the solution was to lower down base frequency to 50 MHz.
  I checked my card in live 11.04 and it works fine, but the speed is even lower, about 11MB/s.

  Technical details:

  $ cat /proc/version_signature
  Ubuntu 4.2.0-30.36~14.04.1-generic 4.2.8-ckt3

  $ dmesg | grep mmc0
  [    1.934510] mmc0: SDHCI controller on PCI [0000:0d:00.0] using DMA
  [    2.012509] mmc0: new high speed SDXC card at address 59b4
  [    2.014409] mmcblk0: mmc0:59b4 NCard 59.0 GiB

  $ dmesg | grep sdhci
  [    1.929073] sdhci: Secure Digital Host Controller Interface driver
  [    1.929076] sdhci: Copyright(c) Pierre Ossman
  [    1.931077] sdhci-pci 0000:0d:00.0: SDHCI controller found [1180:e822] (rev 7)
  [    1.931611] sdhci-pci 0000:0d:00.0: No vmmc regulator found
  [    1.931613] sdhci-pci 0000:0d:00.0: No vqmmc regulator found

  Note:
  After cold boot I see in dmesg
       SDHCI controller found [1180:e823] (rev 4)
  but after reboot or sleep it changes to
       SDHCI controller found [1180:e822] (rev 7)

  Proposal:
  It is possible to control MMC base frequency manually (i.e. by running sdhci-pci module with needed options) to check the performance on 4.2 kernel on 200 MHz base frequency and be able to low it down for cards that requires that patch.

  Sometimes I see in dmesg
  sdhci-pci 0000:0d:00.0: MMC controller base frequency changed to 50Mhz.
  which indicates that fix of #773524 bug works, but the performance with or without this message is the same.

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