sdhci-esdhc-imx -- MMC 10x slower than it should be

Wolfram Sang w.sang at
Wed Jun 15 06:53:18 EDT 2011


> We are seeing issues with sdhci-esdhc-imx in 2.6.39; performance is
> not what it should be; it is about 10x lower in fact.

Which SoC? 25/35/51/53?

> ...any idea what this comment means? I'd like to eventualy support
> 8BITBUS...

8-Bit bus is not specified in the standard, so it cannot be detected.
Check other drivers where they use MMC_CAP_8_BIT_DATA.

> Part of the problem is that esdhc_writeb_le() does translation of bits
> into breescale format; but readb() does not do translation back, and
> core code uses read-modify-write on the register, for example when
> turning on the LED. What to do there? Translate back? Add shadow
> variable? Get rid of read-modify-write?

Probably the least ugly solution :/

> Any ideas why it is slow?

Your board polls for card-detect, Shawn recently sent a series which
lets you fix that for mx5.

ADMA is marked broken in mainline, cause it didn't work with a number of
cards. Richard sent a patch recently.

Both series could need some more testing :)



Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 |  |
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