[PATCH 2/3] powerpc/esdhc: add property to disable the CMD23

[Kumar Gala]

>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: Chris Ball [mailto:cjb at laptop.org]
>>>>>> Sent: Wednesday, September 12, 2012 4:59 AM
>>>>>> To: Kumar Gala
>>>>>> Cc: Huang Changming-R66093; linuxppc-dev at lists.ozlabs.org list;
>>>>>> linux- mmc at vger.kernel.org; Anton Vorontsov
>>>>>> Subject: Re: [PATCH 2/3] powerpc/esdhc: add property to disable the
>>>>>> CMD23
>>>>>> 
>>>>>> Hi,
>>>>>> 
>>>>>> On Tue, Sep 11 2012, Kumar Gala wrote:
>>>>>>> thanks for the info.  Do you know what's required on controller
>>>>>>> side to handle cards that support CMD23?
>>>>>>> 
>>>>>>> I'm trying to figure out if older controller's on FSL SoCs are
>>>>>>> missing some feature to allow CMD23 to work (vs Auto-CMD23).
>>>>>> 
>>>>>> It seems plausible that it's just not implemented on these
>> controllers.
>>>>>> It's a little strange, since the command's been specified for so
>>>>>> long and we haven't seen any other controllers with problems.  The
>>>>>> patch would be correct if this is true.
>>>>>> 
>>>>> 
>>>>> I didn't find any description about it, but after testing on FSL
>>>> silicones, I got this result:
>>>>> Some silicones support this command, and some silicones don't
>>>>> support
>>>> it, which will cause I/O error.
>>>> 
>>>> Can you list out which SoCs support it and which don't.  Having this
>>>> list will be useful in understanding which controller versions
>> supported it.
>>>> 
>>> P1020, p1021, p1022, p1024, p1015 and p4080 can't support it.
>>> Mpc8536, p2020, and the other current DPAA silicon (e.g. p5020, p3041)
>> support it.
>> 
>> Based on this, why don't we use the HOSTVER register to detect instead of
>> device tree:
>> 
>> 
>> #define FSL_SDHC_VER_1_0	0x00
>> #define FSL_SDHC_VER_1_1	0x01
>> #define FSL_SDHC_VER_2_0	0x10
>> #define FSL_SDHC_VER_2_1	0x11
>> #define FSL_SDHC_VER_2_2	0x12
>> #define FSL_SDHC_VER_2_3	0x13
>> 
>> unsigned int vendor_version;
>> 
>> vendor_version = sdhci_readw(host, SDHCI_HOST_VERSION); vendor_version =
>> (vendor_version & SDHCI_VENDOR_VER_MASK) >> SDHCI_VENDOR_VER_SHIFT;
>> 
>> if ((vendor_version == FSL_SDHC_VER_1_1) || (vendor_version ==
>> FSL_SDHC_VER_2_2))
>> 	host->quirks2 |= SDHCI_QUIRK2_HOST_NO_CMD23;
>> 
> 
> I once thought about it, but if the future silicon does not support this feature,
> then we continue to modify these codes for new silicon?

Yes, but it seems extremely unlikely that future versions of the controller will remove this feature now that it exists.

- k