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Commit adc7dca4 authored by Bojun Pan's avatar Bojun Pan Committed by Gerrit - the friendly Code Review server
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msm: gsi: Avoid unnessary write to ipa 



Only write to ipa to reset channel interrupt, when there
is no entry. Do a read of read pointer after write to close
a small window. The sequence is as such in the poll channel:
 If sw needs to update sw read pointer, it does,
  step 1. update read pointer from ipa,
  step 2  if there is no event, write to reset channel
    interrupt.
  step 3, to close window between step 1 and step2 that
    may have new events, do another read of read pointer.
    And if no more entry then, return EMPTY.
    Otherwise proceeed to process entries as before.

Change-Id: I68b983111416b617b835de024a22c47517ea7f3e
Signed-off-by: default avatarBojun Pan <bojunp@codeaurora.org>
parent 99080dfb

drivers/platform/msm/gsi/gsi.c

+21 −9
Original line number Diff line number Diff line
@@ -3597,20 +3597,32 @@ int gsi_poll_n_channel(unsigned long chan_hdl, 
	spin_lock_irqsave(&ctx->evtr->ring.slock, flags);

	if (ctx->evtr->ring.rp == ctx->evtr->ring.rp_local) {

		/* update rp to see of we have anything new to process */

		gsi_writel(1 << ctx->evtr->id, gsi_ctx->base +

			GSI_EE_n_CNTXT_SRC_IEOB_IRQ_CLR_OFFS(ee));

		rp = gsi_readl(gsi_ctx->base +

			GSI_EE_n_EV_CH_k_CNTXT_4_OFFS(ctx->evtr->id, ee));

		rp |= ctx->ring.rp & 0xFFFFFFFF00000000;

		rp |= ctx->ring.rp & 0xFFFFFFFF00000000ULL;



		ctx->evtr->ring.rp = rp;

	}



	if (ctx->evtr->ring.rp == ctx->evtr->ring.rp_local) {

		spin_unlock_irqrestore(&ctx->evtr->ring.slock, flags);

		/* read gsi event ring rp again if last read is empty */

		if (rp == ctx->evtr->ring.rp_local) {

			/* event ring is empty */

			gsi_writel(1 << ctx->evtr->id, gsi_ctx->base +

				GSI_EE_n_CNTXT_SRC_IEOB_IRQ_CLR_OFFS(ee));

			/* do another read to close a small window */

			__iowmb();

			rp = gsi_readl(gsi_ctx->base +

				GSI_EE_n_EV_CH_k_CNTXT_4_OFFS(

				ctx->evtr->id, ee));

			rp |= ctx->ring.rp & 0xFFFFFFFF00000000ULL;

			ctx->evtr->ring.rp = rp;

			if (rp == ctx->evtr->ring.rp_local) {

				spin_unlock_irqrestore(

					&ctx->evtr->ring.slock,

					flags);

				ctx->stats.poll_empty++;

				return GSI_STATUS_POLL_EMPTY;

			}

		}

	}



	*actual_num = gsi_get_complete_num(&ctx->evtr->ring,

			ctx->evtr->ring.rp_local, ctx->evtr->ring.rp);