linux-kernel - [PATCH v1] memory: tegra: Check whether reset is already asserted

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Date:   Wed, 20 Jan 2021 02:52:10 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] memory: tegra: Check whether reset is already asserted

Check whether memory client reset is already asserted in order to prevent
DMA-flush error on trying to re-assert an already asserted reset.

This becomes a problem once PMC GENPD is enabled to use memory resets
since GENPD will get a error and fail to toggle power domain. PMC GENPDs
can't be toggled safely without holding memory reset on Tegra and we're
about to fix this.

Tested-by: Peter Geis <pgwipeout@...il.com> # Ouya T30
Tested-by: Dmitry Osipenko <digetx@...il.com> # A500 T20 and Nexus7 T30
Tested-by: Nicolas Chauvet <kwizart@...il.com> # PAZ00 T20
Tested-by: Matt Merhar <mattmerhar@...tonmail.com> # Ouya T30
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/memory/tegra/mc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
index 44064de962c2..a21163ccadc4 100644
--- a/drivers/memory/tegra/mc.c
+++ b/drivers/memory/tegra/mc.c
@@ -176,6 +176,13 @@ static int tegra_mc_hotreset_assert(struct reset_controller_dev *rcdev,
 	if (!rst_ops)
 		return -ENODEV;
 
+	/* DMA flushing will fail if reset is already asserted */
+	if (rst_ops->reset_status) {
+		/* check whether reset is asserted */
+		if (rst_ops->reset_status(mc, rst))
+			return 0;
+	}
+
 	if (rst_ops->block_dma) {
 		/* block clients DMA requests */
 		err = rst_ops->block_dma(mc, rst);
-- 
2.29.2