linux-kernel - [PATCH] mmc: mmci_sdmmc: fix power on issue due to pwr

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Date:   Mon, 20 Apr 2020 18:18:31 +0200
From:   Ludovic Barre <ludovic.barre@...com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
CC:     <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        Ludovic Barre <ludovic.barre@...com>
Subject: [PATCH] mmc: mmci_sdmmc: fix power on issue due to pwr_reg initialization

This patch fix a power-on issue, and avoid to retry the power sequence.

In power off sequence: sdmmc must set pwr_reg in "power-cycle" state
(value 0x2), to prevent the card from being supplied through the signal
lines (all the lines are driven low).

In power on sequence: when the power is stable, sdmmc must set pwr_reg
in "power-off" state (value 0x0) to drive all signal to high before to
set "power-on".

To avoid writing the same value to the power register several times, this
register is cached by the pwr_reg variable. At probe pwr_reg is initialized
to 0 by kzalloc of mmc_alloc_host.

Like pwr_reg value is 0 at probing, the power on sequence fail because
the "power-off" state is not writes (value 0x0) and the lines
remain drive to low.

This patch initializes "pwr_reg" variable with power register value.
This it done in sdmmc variant init to not disturb default mmci behavior.

Signed-off-by: Ludovic Barre <ludovic.barre@...com>
---

This patch is the proposal from:
https://patchwork.kernel.org/patch/11457987/

---
 drivers/mmc/host/mmci_stm32_sdmmc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
index d33e62bd6153..14f99d8aa3f0 100644
--- a/drivers/mmc/host/mmci_stm32_sdmmc.c
+++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
@@ -519,6 +519,7 @@ void sdmmc_variant_init(struct mmci_host *host)
 	struct sdmmc_dlyb *dlyb;

 	host->ops = &sdmmc_variant_ops;
+	host->pwr_reg = readl_relaxed(host->base + MMCIPOWER);

 	base_dlyb = devm_of_iomap(mmc_dev(host->mmc), np, 1, NULL);
 	if (IS_ERR(base_dlyb))
-- 
2.17.1