linux-kernel - [PATCH] mmc: mmci: use peripheral flow control for STM32

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Message-ID: <20230927184556.1422122-1-ben.wolsieffer@hefring.com>
Date:   Wed, 27 Sep 2023 14:45:56 -0400
From:   Ben Wolsieffer <ben.wolsieffer@...ring.com>
To:     linux-stm32@...md-mailman.stormreply.com,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Russell King <linux@...linux.org.uk>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Yann Gautier <yann.gautier@...s.st.com>,
        Christophe Kerello <christophe.kerello@...s.st.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ben Wolsieffer <Ben.Wolsieffer@...ring.com>
Subject: [PATCH] mmc: mmci: use peripheral flow control for STM32

From: Ben Wolsieffer <Ben.Wolsieffer@...ring.com>

The STM32 SDMMC peripheral (at least for the STM32F429, STM32F469 and
STM32F746, which are all the currently supported devices using periphid
0x00880180) requires DMA to be performed in peripheral flow controller
mode. From the STM32F74/5 reference manual, section 35.3.2:

"SDMMC host allows only to use the DMA in peripheral flow controller
mode. DMA stream used to serve SDMMC must be configured in peripheral
flow controller mode"

This patch adds a variant option to control peripheral flow control and
enables it for the STM32 variant.

Signed-off-by: Ben Wolsieffer <Ben.Wolsieffer@...ring.com>
---
 drivers/mmc/host/mmci.c | 3 ++-
 drivers/mmc/host/mmci.h | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 769b34afa835..90e32f18abbc 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -249,6 +249,7 @@ static struct variant_data variant_stm32 = {
 	.f_max			= 48000000,
 	.pwrreg_clkgate		= true,
 	.pwrreg_nopower		= true,
+	.dma_flow_controller	= true,
 	.init			= mmci_variant_init,
 };
 
@@ -1012,7 +1013,7 @@ static int _mmci_dmae_prep_data(struct mmci_host *host, struct mmc_data *data,
 		.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES,
 		.src_maxburst = variant->fifohalfsize >> 2, /* # of words */
 		.dst_maxburst = variant->fifohalfsize >> 2, /* # of words */
-		.device_fc = false,
+		.device_fc = variant->dma_flow_controller,
 	};
 	struct dma_chan *chan;
 	struct dma_device *device;
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index 253197f132fc..9a81f30f6748 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -332,6 +332,7 @@ enum mmci_busy_state {
  * @opendrain: bitmask identifying the OPENDRAIN bit inside MMCIPOWER register
  * @dma_lli: true if variant has dma link list feature.
  * @stm32_idmabsize_mask: stm32 sdmmc idma buffer size.
+ * @dma_flow_controller: use peripheral as flow controller for DMA.
  */
 struct variant_data {
 	unsigned int		clkreg;
@@ -378,6 +379,7 @@ struct variant_data {
 	u8			dma_lli:1;
 	u32			stm32_idmabsize_mask;
 	u32			stm32_idmabsize_align;
+	u8			dma_flow_controller:1;
 	void (*init)(struct mmci_host *host);
 };
 
-- 
2.42.0