mmc_test Correct xfer_size at write

mmc_test Correct xfer_size at write

[James Hogan]

Hi,

I'm trying to figure out why the broken write transfer tests in mmc_test
require the result to be -ETIMEDOUT, so that I can make dw_mmc pass
these tests. Perhaps somebody could explain.

I can understand for reads, that the controller is waiting for the start
bit on the data lines and so it can timeout after a while if it doesn't
see any. However for writes (as far as I can glean from the physical
layer spec and a logic analyser) the data response token which is
normally sent by the card in response to a write transfer is clocked out
immediately after the data so is either there or it isn't.

Have I misunderstood it or is -ETIMEDOUT just the error that is required
by convention when the data response token is not detected?

Thanks

James

mmc_test Correct xfer_size at write

[James Hogan]

Hi,

I'm trying to figure out why the broken write transfer tests in mmc_test
require the result to be -ETIMEDOUT, so that I can make dw_mmc pass
these tests. Perhaps somebody could explain.

I can understand for reads, that the controller is waiting for the start
bit on the data lines and so it can timeout after a while if it doesn't
see any. However for writes (as far as I can glean from the physical
layer spec and a logic analyser) the data response token which is
normally sent by the card in response to a write transfer is clocked out
immediately after the data so is either there or it isn't.

Have I misunderstood it or is -ETIMEDOUT just the error that is required
by convention when the data response token is not detected?

Thanks

James

Re: mmc_test Correct xfer_size at write

[Pierre Ossman]

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On Tue, 28 Jun 2011 11:37:25 +0100
James Hogan <james.hogan@imgtec.com> wrote:

> Hi,
> 
> I'm trying to figure out why the broken write transfer tests in mmc_test
> require the result to be -ETIMEDOUT, so that I can make dw_mmc pass
> these tests. Perhaps somebody could explain.
> 
> I can understand for reads, that the controller is waiting for the start
> bit on the data lines and so it can timeout after a while if it doesn't
> see any. However for writes (as far as I can glean from the physical
> layer spec and a logic analyser) the data response token which is
> normally sent by the card in response to a write transfer is clocked out
> immediately after the data so is either there or it isn't.
> 
> Have I misunderstood it or is -ETIMEDOUT just the error that is required
> by convention when the data response token is not detected?
> 

It's more or less by convention. ETIMEDOUT is the closest thing we have
to "we expected a response from the card but got bupkis". You can find
some informal definitions here:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=include/linux/mmc/core.h;h=b6718e549a510780e0f8c9a3be17e64753d6c2f5;hb=HEAD#l81

Rgds
-- 
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Re: mmc_test Correct xfer_size at write

[James Hogan]

On 06/28/2011 05:50 PM, Pierre Ossman wrote:
> On Tue, 28 Jun 2011 11:37:25 +0100
> James Hogan <james.hogan@imgtec.com> wrote:
> 
>> Hi,
>>
>> I'm trying to figure out why the broken write transfer tests in mmc_test
>> require the result to be -ETIMEDOUT, so that I can make dw_mmc pass
>> these tests. Perhaps somebody could explain.
>>
>> I can understand for reads, that the controller is waiting for the start
>> bit on the data lines and so it can timeout after a while if it doesn't
>> see any. However for writes (as far as I can glean from the physical
>> layer spec and a logic analyser) the data response token which is
>> normally sent by the card in response to a write transfer is clocked out
>> immediately after the data so is either there or it isn't.
>>
>> Have I misunderstood it or is -ETIMEDOUT just the error that is required
>> by convention when the data response token is not detected?
>>
> 
> It's more or less by convention. ETIMEDOUT is the closest thing we have
> to "we expected a response from the card but got bupkis". You can find
> some informal definitions here:
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=include/linux/mmc/core.h;h=b6718e549a510780e0f8c9a3be17e64753d6c2f5;hb=HEAD#l81
> 
> Rgds

Thanks for the info Pierre

James