linux-kernel - [PATCH] mmc: sdhci-cadence: fix PHY write

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Date:   Mon, 25 May 2020 10:40:53 +0300
From:   Vladimir Kondratiev <vladimir.kondratiev@...el.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org
Cc:     Vladimir Kondratiev <vladimir.kondratiev@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mmc: sdhci-cadence: fix PHY write

Accordingly to Cadence documentation, PHY write procedure is:

1. Software sets the PHY Register Address (HRS04[5:0]) and the
   PHY Write Data (HRS04[15:8]) fields.
2. Software sets the PHY Write Transaction Request (HRS04[24]) field to 1.
3. Software waits as the PHY Write Transaction Acknowledge (HRS04[26])
   field is equal to 0.
4. Hardware performs the write transaction to PHY register where
   HRS04[15:8] is a data written to register under HRS04[5:0] address.
5. Hardware sets the PHY Transaction Acknowledge (HRS04[26]) to 1 when
   transaction is completed.
6. Software clears the PHY Write Transaction Request (HRS04[24]) to 1
   after noticing that the PHY Write Transaction Acknowledge (HRS04[26])
   field is equal to 1.
7. Software waits for the PHY Acknowledge Register (HRS04[26]) field is
   equal to 0.

Add missing steps 3 and 7. Lack of these steps causes
integrity errors detested by hardware.

Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@...el.com>
---
 drivers/mmc/host/sdhci-cadence.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index e474d3fa099e..6b2e7c43cbc1 100644
--- a/drivers/mmc/host/sdhci-cadence.c
+++ b/drivers/mmc/host/sdhci-cadence.c
@@ -114,6 +114,11 @@ static int sdhci_cdns_write_phy_reg(struct sdhci_cdns_priv *priv,
 	u32 tmp;
 	int ret;

+	ret = readl_poll_timeout(reg, tmp, !(tmp & SDHCI_CDNS_HRS04_ACK),
+				 0, 10);
+	if (ret)
+		return ret;
+
 	tmp = FIELD_PREP(SDHCI_CDNS_HRS04_WDATA, data) |
 	      FIELD_PREP(SDHCI_CDNS_HRS04_ADDR, addr);
 	writel(tmp, reg);
@@ -128,7 +133,10 @@ static int sdhci_cdns_write_phy_reg(struct sdhci_cdns_priv *priv,
 	tmp &= ~SDHCI_CDNS_HRS04_WR;
 	writel(tmp, reg);

-	return 0;
+	ret = readl_poll_timeout(reg, tmp, !(tmp & SDHCI_CDNS_HRS04_ACK),
+				 0, 10);
+
+	return ret;
 }

 static unsigned int sdhci_cdns_phy_param_count(struct device_node *np)
-- 
2.20.1

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