linux-kernel - Re: [RFC PATCH 4/4] mmc: sdhci-of-arasan: overwrite enhanced strobe callback

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Date:	Thu, 3 Mar 2016 19:37:17 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Michal Simek <michal.simek@...inx.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, shawn.lin@...nel-upstream.org,
	soren.brinkmann@...inx.com, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 4/4] mmc: sdhci-of-arasan: overwrite enhanced strobe
 callback

On 2016/3/3 19:02, Michal Simek wrote:
> On 3.3.2016 03:36, Shawn Lin wrote:
>> Currently sdhci-arasan 5.1 can support enhanced strobe function,
>> but considering the potential requirement in the future for other
>> version IP, we don't limit it just for "arasan,sdhci-5.1". Add
>> cap-enhanced-strobe in DT to enable the function if we'r sure our
>> controller can support it.
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>   drivers/mmc/host/sdhci-of-arasan.c | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
>> index 1e4b5e0..31f3494 100644
>> --- a/drivers/mmc/host/sdhci-of-arasan.c
>> +++ b/drivers/mmc/host/sdhci-of-arasan.c
>> @@ -24,7 +24,9 @@
>>   #include "sdhci-pltfm.h"
>>
>>   #define SDHCI_ARASAN_CLK_CTRL_OFFSET	0x2c
>> +#define SDHCI_ARASAN_VENDOR_REGISTER	0x78
>
> I was checking our register map and we even don't have this register
> listed as reserved.
> It looks like that this will be related to certain SoC and different SoC
> can use it different location.
> That's why I think this feature and setup should be related to certain
> SoC specific compatible string.

Hi Michal,

I think that is IP version specific because it's inside controller's
databook. But I only have a datasheet released by arasan for 5.1 
controller, so I didn't know if your databook has this register. And
I can't find sdhci spec has a reg to enable this feature either. Looks
strange, but maybe you are right: it also related to certain Soc for
other sdhci variant drivers. But for sdhci-of-arsan, it more likes to
use this register from now on for the future IP version to enable this
feature inside the controller register-range.

Thanks for checking that. Now, I'm more sure about that we should limit
it for 5.1 currently by checking the compatible string.

I expect more comments from ulf and adrian about the other part of code
until I respin the next version.

>
> Thanks,
> Michal
>
>
>
>

-- 
Best Regards
Shawn Lin