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SubjectRe: [PATCH v2 3/3] pm: at91: add disable/enable the L1/L2 cache while suspend/resume
On Wed, Jan 28, 2015 at 10:24:04AM +0800, Wenyou Yang wrote:
> + /*
> + * Clean and invalidate the L2 cache.
> + * Common cache-l2x0.c functions can't be used here since it
> + * uses spinlocks. We are out of coherency here with data cache
> + * disabled. The spinlock implementation uses exclusive load/store
> + * instruction which can fail without data cache being enabled.
> + * Because of this, CPU can lead to deadlock.

We really need to stop needing platforms to create their own L2 handling
code. Please move this to a helper function in arch/arm/mm/l2c-l...-clean.S,
replacing ... with the appropriate part for the code fragment.

> + */
> + ldr r1, at91_l2cc_base_addr
> + ldr r2, [r1]
> + cmp r2, #0
> + beq skip_l2disable
> + mov r0, #0xff
> + str r0, [r2, #L2X0_CLEAN_INV_WAY]
> +wait:
> + ldr r0, [r2, #L2X0_CLEAN_INV_WAY]
> + mov r1, #0xff
> + ands r0, r0, r1
> + bne wait
> +
> + mov r0, #0
> + str r0, [r2, #L2X0_CTRL]
> +
> +l2x_sync:
> + ldr r0, [r2, #L2X0_CACHE_SYNC]
> + bic r0, r0, #0x1
> + str r0, [r2, #L2X0_CACHE_SYNC]

I wonder whether you've actually read the documentation for this. You
don't need to read-modify-write this register. The C code doesn't even
do this. A write to this register is sufficient - a write issues the
sync, a read returns the completion status.

> +sync:
> + ldr r0, [r2, #L2X0_CACHE_SYNC]
> + ands r0, r0, #0x1
> + bne sync

Moreover, do you actually need this - it depends on the L2C model. Only
L2C220 needs to spin waiting for the sync operation to complete.

Also, are you sure the "clean+invalidate, disable, sync" sequence is
correct? Should it not be "clean+invalidate, sync, disable" ?

--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.


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