linux-kernel - [PATCH V1 02/11] mmc: sdhci: allow host to specify maximum tuning loops

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Date:   Fri, 1 Mar 2019 21:20:16 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     <adrian.hunter@...el.com>, <ulf.hansson@...aro.org>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <riteshh@...eaurora.org>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <anrao@...dia.com>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        Sowjanya Komatineni <skomatineni@...dia.com>
Subject: [PATCH V1 02/11] mmc: sdhci: allow host to specify maximum tuning loops

As per the Host Controller Standard Specification Version 4.20,
limitation of tuning iteration count is removed as PLL locking
time can be longer than UHS-1 tuning due to larger PVT fluctuation
and it will result in increase of tuning iteration to complete the
tuning.

This patch creates a hook get_max_tuning_loop_count to allow hosts
to specify maximum tuning iterations and updates execute_tuning
to use the specified maximum tuning iteration count.

Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
---
 drivers/mmc/host/sdhci.c | 7 +++++--
 drivers/mmc/host/sdhci.h | 1 +
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index a8141ff9be03..e9e919218006 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2366,12 +2366,15 @@ EXPORT_SYMBOL_GPL(sdhci_send_tuning);
 static int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
 {
 	int i;
+	int tuning_loop_count = MAX_TUNING_LOOP;
 
+	if (host->ops->get_max_tuning_loop_count)
+		tuning_loop_count = host->ops->get_max_tuning_loop_count(host);
 	/*
 	 * Issue opcode repeatedly till Execute Tuning is set to 0 or the number
-	 * of loops reaches 40 times.
+	 * of loops reaches tuning loop count.
 	 */
-	for (i = 0; i < MAX_TUNING_LOOP; i++) {
+	for (i = 0; i < tuning_loop_count; i++) {
 		u16 ctrl;
 
 		sdhci_send_tuning(host, opcode);
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 01002cba1359..c80e0d6f9b10 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -638,6 +638,7 @@ struct sdhci_ops {
 	unsigned int    (*get_ro)(struct sdhci_host *host);
 	void		(*reset)(struct sdhci_host *host, u8 mask);
 	int	(*platform_execute_tuning)(struct sdhci_host *host, u32 opcode);
+	int	(*get_max_tuning_loop_count)(struct sdhci_host *host);
 	void	(*set_uhs_signaling)(struct sdhci_host *host, unsigned int uhs);
 	void	(*hw_reset)(struct sdhci_host *host);
 	void    (*adma_workaround)(struct sdhci_host *host, u32 intmask);
-- 
2.7.4