Hi Ravikumar, + Alex, 在 2016/10/3 18:43, Ravikumar Kattekola 写道:
Hi all, I’ve seen an eMMC failure due to pending background operations on a certain OMAP device since bkops enable bit was not set. Further investigation showed me that someone already posted patch to enable Background operations in kernel based on a host capability check (Caps2 & BK_OPS_EN) but was turned down quoting that it should be enabled from user space using mmc-utils. Enabling this would add one additional check for exception event in the response R1 or R1B (only on hosts that explicitly set BK_OPS_EN in caps2). But not enabling this could lead to a system failure especially when the Filesystem is on eMMC and the card stops responding due to pending critical bkops. I would like to ask for expert opinion on ‘why is it a bad idea to enable bkops in kernel?’
Some discussion about the similar topic could be found here: https://patchwork.kernel.org/patch/9157121/
It’s a one time programmable bit but if it helps in keeping system functional why not do it?
Actually BKOPS_EN is not OTP bit.. Quoted from Ulf "I don't have any issue to allow all non-OTP registers bits to be written." So I guess you could do this, although it needs more discussion there. But it's persistent EXT_CSD register and we get used to control it from userspace, which is the policy we have been sticking to when writing to persistent EXT_CSD registers. I guess that is nothing about "right and wrong", just a rule for us in case someone wants to set the persistent bit in kernel but setting other persistent bits from user-space, which is prone to mess up the mmc core. Or, someone will sent mail to the list asking "why is it a good idea to enable bkops in kernel" ? :)
I haven’t measured the performance impact but I don’t see a reason for major drop because the frequency of critical bkops events would be less. Regards, RK -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
-- Best Regards Shawn Lin -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
