Re: [PATCH v9] mmc: support BKOPS feature for eMMC

[Chris Ball <cjb@laptop.org>]

Hi,

On Sun, Jul 08 2012, Jaehoon Chung wrote:
>> I think MMC_CAP2_BKOPS should be removed. If the card BKOPs were already
>> enabled, the host must support BKOPs. Therefore, in mmc_start_bkops we
>> should check only if card->ext_csd.bkops_en is set.
>
> If bkops bit is set, it means that use the bkops by default.
> If somebody didn't want to use the bkops, then just didn't set the MMC_CAP2_BKOPS.
> And eMMC card's BKOPS bit should not be set,
> then we can set the BKOPS support with switch command.
> For this, MMC_CAP2_INIT_BKOPS is added.
> In my case, didn't set the bkops enable bit at first time.
> So need to set bkops enable bit with switch command.
>
> As Maya's mentioned, if we use the bkops by default, we can remove the MMC_CAP2_BKOPS2.

I'm not sure I understand.  If someone has advertised MMC_CAP2_BKOPS on
their host, why do we also need to check for MMC_CAP2_INIT_BKOPS before
we enable it in the ext_csd?

Why shouldn't we just use one (MMC_CAP2_BKOPS) capability to mean
"enable bkops if supported, by writing 1 (if it wasn't already set)
to ext_csd[163] to tell the card that we're going to be using bkops"?
Are there any disadvantages to doing this?

Thanks,

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child