linux-kernel - [PATCH V2] mmc: sdhci-msm: Don't enable PWRSAVE

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Date:   Fri,  7 Feb 2020 17:34:28 +0530
From:   Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
To:     ulf.hansson@...aro.org, adrian.hunter@...el.com
Cc:     asutoshd@...eaurora.org, stummala@...eaurora.org,
        sayalil@...eaurora.org, cang@...eaurora.org,
        rampraka@...eaurora.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Ritesh Harjani <riteshh@...eaurora.org>,
        Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: [PATCH V2] mmc: sdhci-msm: Don't enable PWRSAVE_DLL for certain sdhc hosts

From: Ritesh Harjani <riteshh@...eaurora.org>

SDHC core with new 14lpp and later tech DLL should not enable
PWRSAVE_DLL since such controller's internal gating cannot meet
following MCLK requirement:
When MCLK is gated OFF, it is not gated for less than 0.5us and MCLK
must be switched on for at-least 1us before DATA starts coming.

Adding support for this requirement.

Signed-off-by: Ritesh Harjani <riteshh@...eaurora.org>
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
--

Changes since V1:
  Condition was not correct in V1, which is corrected in V2

--
---
 drivers/mmc/host/sdhci-msm.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index c3a160c..aa5b610 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -977,9 +977,21 @@ static int sdhci_msm_cm_dll_sdc4_calibration(struct sdhci_host *host)
 		goto out;
 	}
 
-	config = readl_relaxed(host->ioaddr + msm_offset->core_vendor_spec3);
-	config |= CORE_PWRSAVE_DLL;
-	writel_relaxed(config, host->ioaddr + msm_offset->core_vendor_spec3);
+	/*
+	 * Set CORE_PWRSAVE_DLL bit in CORE_VENDOR_SPEC3.
+	 * When MCLK is gated OFF, it is not gated for less than 0.5us
+	 * and MCLK must be switched on for at-least 1us before DATA
+	 * starts coming. Controllers with 14lpp and later tech DLL cannot
+	 * guarantee above requirement. So PWRSAVE_DLL should not be
+	 * turned on for host controllers using this DLL.
+	 */
+	if (!msm_host->use_14lpp_dll_reset) {
+		config = readl_relaxed(host->ioaddr +
+				msm_offset->core_vendor_spec3);
+		config |= CORE_PWRSAVE_DLL;
+		writel_relaxed(config, host->ioaddr +
+				msm_offset->core_vendor_spec3);
+	}
 
 	/*
 	 * Drain writebuffer to ensure above DLL calibration
-- 
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