From 197160d52e859575ff0ad1afd674ab2a825b9f83 Mon Sep 17 00:00:00 2001 From: Nick Sanders Date: Tue, 6 May 2014 18:52:38 -0700 Subject: [PATCH] mmc: sdhci: remove mdelay in eMMC tuning This patch removes an unneccesary 1ms mdelay in the HS200 tuning loop, called 40 times per retuning. Currently this causes a latency of >40ms on any emmc accesses triggering wake from runtime PM, which can occur for a significant portion of reads on a mostly idle system. The delay is left in place for SD Cards, which use MMC_SEND_TUNING_BLOCK rather than MMC_SEND_TUNING_BLOCK_HS200. I'm not able to find evidence that this is required for SD in the specs I have access to, however this delay has been present from initial checkin for SD so I have preserved the original behavior for compatibility. This has been verified to fix observed glitching on local audio playback and recording on apps with inbuilt assumptions on storage latency. Signed-off-by: Nick Sanders Reviewed-by: Grant Grundler Reviewed-by: Doug Anderson Acked-by: Ulf Hansson Signed-off-by: Chris Ball --- drivers/mmc/host/sdhci.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index a31f06dadf6f..255aaf18db35 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -1994,7 +1994,10 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode) ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2); tuning_loop_counter--; timeout--; - mdelay(1); + + /* eMMC spec does not require a delay between tuning cycles */ + if (opcode == MMC_SEND_TUNING_BLOCK) + mdelay(1); } while (ctrl & SDHCI_CTRL_EXEC_TUNING); /* -- 2.11.0