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ARM: qcom: scm: Flush the command buffer only instead of the entire cache 

scm_call flushes the entire cache before calling into the secure world.
This is both a performance penalty as well as insufficient on SMP systems
where the CPUs possess a write-back L1 cache. Flush only the command and
response buffers instead, moving the responsibility of flushing any other
cached buffer (being passed to the secure world) to callers.

Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
This commit is contained in:
Vikram Mulukutla 2014-08-04 18:31:45 -07:00 committed by Kumar Gala
parent 30cbb0c01b
commit 404b5a97f5
1 changed files with 12 additions and 5 deletions
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17
arch/arm/mach-qcom/scm.c
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@ -196,12 +196,12 @@ static int __scm_call(const struct scm_command *cmd)
u32 cmd_addr = virt_to_phys(cmd);
/*
* Flush the entire cache here so callers don't have to remember
* to flush the cache when passing physical addresses to the secure
* side in the buffer.
* Flush the command buffer so that the secure world sees
* the correct data.
*/
flush_cache_all();
outer_flush_all();
__cpuc_flush_dcache_area((void *)cmd, cmd->len);
outer_flush_range(cmd_addr, cmd_addr + cmd->len);
ret = smc(cmd_addr);
if (ret < 0)
ret = scm_remap_error(ret);
@ -238,6 +238,13 @@ static void scm_inv_range(unsigned long start, unsigned long end)
* @resp_len: length of the response buffer
*
* Sends a command to the SCM and waits for the command to finish processing.
*
* A note on cache maintenance:
* Note that any buffers that are expected to be accessed by the secure world
* must be flushed before invoking scm_call and invalidated in the cache
* immediately after scm_call returns. Cache maintenance on the command and
* response buffers is taken care of by scm_call; however, callers are
* responsible for any other cached buffers passed over to the secure world.
*/
int scm_call(u32 svc_id, u32 cmd_id, const void *cmd_buf, size_t cmd_len,
void *resp_buf, size_t resp_len)