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Commit 404b5a97 authored by Vikram Mulukutla's avatar Vikram Mulukutla Committed by Kumar Gala
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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: default avatarVikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: default avatarKumar Gala <galak@codeaurora.org>
parent 30cbb0c0

arch/arm/mach-qcom/scm.c

+12 −5
Original line number Diff line number Diff line
@@ -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)