Re: [PATCH] tmio_mmc: Prevents unexpected status clear

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 13 Jul 2010 10:16:39 +0900
Yusuke Goda <yusuke.goda.sx@renesas.com> wrote:

> Hi Andrew
> 
> Thank you for your comment.
> 
> >>  #define ack_mmc_irqs(host, i) \
> >>  	do { \
> >> -		u32 mask;\
> >> -		mask  = sd_ctrl_read32((host), CTL_STATUS); \
> >> -		mask &= ~((i) & TMIO_MASK_IRQ); \
> >> -		sd_ctrl_write32((host), CTL_STATUS, mask); \
> >> +		sd_ctrl_write32((host), CTL_STATUS, ~(i)); \
> >>  	} while (0)
> > 
> > Can we have a better changelog please?
> > 
> > What was wrong with the old code?
> > 
> > How does the patch fix it?
> > 
> > What are the user-visible runtime effects of the bug?
> > 
> > (It looks like that was a pretty gross bug - how did it pass testing??)
> Example
>  - CMD53(Single block read / Received data size : 64Byte)
> 
>  1) Send CMD53
>  2) Receive "CMD53 response"
>  3) Call tmio_mmc_cmd_irq(host, status);
> -- original code ----------------------------------------------------
>  #define ack_mmc_irqs(host, i) \
> 	do { \
> 		u32 mask;\
> 		mask  = sd_ctrl_read32((host), CTL_STATUS); \
> 	< case 1 >
> 		mask &= ~((i) & TMIO_MASK_IRQ); \
> 	< case 2 >
> 		sd_ctrl_write32((host), CTL_STATUS, mask); \
> 	} while (0)
> ---------------------------------------------------------------------
> 
> TMIO_STAT_RXRDY status will be cleared by "sd_ctrl_write32((host), CTL_STATUS, mask);"
> if TMIO_STAT_RXRDY becomes effective between "< case 1 >" and "< case 2 >".
> 
> This causes the phenomenon that a TMIO_STAT_RXRDY interrupt does not occur.
> When received data are small, it rarely occurs.
> 

OK..

But with both this patch and "tmio_mmc-revise-limit-on-data-size.patch"
the changelogs fail to describe the impact of the bug upon our users. 
So when I sit here trying to work out whether the patches should be
applied to 2.6.35 and whether they should be backported into -stable, I
don't have enough information.

What are your thoughts on this?