linux-kernel - [PATCH] spi: meson-spicc: move wait completion in driver to take bursts delay in account

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Message-Id: <20221026-spicc-burst-delay-v1-0-1be5ffb7051a@linaro.org>
Date:   Wed, 26 Oct 2022 09:58:28 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Mark Brown <broonie@...nel.org>,
        Kevin Hilman <khilman@...libre.com>
Cc:     linux-arm-kernel@...ts.infradead.org, Da Xue <da@...re.computer>,
        linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        linux-spi@...r.kernel.org
Subject: [PATCH] spi: meson-spicc: move wait completion in driver to take
 bursts delay in account

Some delay occurs between each bursts, thus the default delay is wrong
and a timeout will occur with big enough transfers.

The solution is to handle the timeout management in the driver and
add some delay for each bursts in the timeout calculation.

Reported-by: Da Xue <da@...re.computer>
Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
---
To: Mark Brown <broonie@...nel.org>
To: Kevin Hilman <khilman@...libre.com>
To: Jerome Brunet <jbrunet@...libre.com>
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: linux-spi@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-amlogic@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/spi/spi-meson-spicc.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-meson-spicc.c b/drivers/spi/spi-meson-spicc.c
index bad201510a99..52bffab18329 100644
--- a/drivers/spi/spi-meson-spicc.c
+++ b/drivers/spi/spi-meson-spicc.c
@@ -160,6 +160,7 @@ struct meson_spicc_device {
 	struct clk			*clk;
 	struct spi_message		*message;
 	struct spi_transfer		*xfer;
+	struct completion		done;
 	const struct meson_spicc_data	*data;
 	u8				*tx_buf;
 	u8				*rx_buf;
@@ -282,7 +283,7 @@ static irqreturn_t meson_spicc_irq(int irq, void *data)
 		/* Disable all IRQs */
 		writel(0, spicc->base + SPICC_INTREG);
 
-		spi_finalize_current_transfer(spicc->master);
+		complete(&spicc->done);
 
 		return IRQ_HANDLED;
 	}
@@ -386,6 +387,7 @@ static int meson_spicc_transfer_one(struct spi_master *master,
 				    struct spi_transfer *xfer)
 {
 	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
+	unsigned long timeout;
 
 	/* Store current transfer */
 	spicc->xfer = xfer;
@@ -410,13 +412,29 @@ static int meson_spicc_transfer_one(struct spi_master *master,
 	/* Setup burst */
 	meson_spicc_setup_burst(spicc);
 
+	/* Setup wait for completion */
+	reinit_completion(&spicc->done);
+
+	/* For each byte we wait for 8 cycles of the SPI clock */
+	timeout = 8LL * MSEC_PER_SEC * xfer->len;
+	do_div(timeout, xfer->speed_hz);
+
+	/* Add 10us delay between each fifo bursts */
+	timeout += ((xfer->len >> 4) * 10) / MSEC_PER_SEC;
+
+	/* Increase it twice and add 200 ms tolerance */
+	timeout += timeout + 200;
+
 	/* Start burst */
 	writel_bits_relaxed(SPICC_XCH, SPICC_XCH, spicc->base + SPICC_CONREG);
 
 	/* Enable interrupts */
 	writel_relaxed(SPICC_TC_EN, spicc->base + SPICC_INTREG);
 
-	return 1;
+	if (!wait_for_completion_timeout(&spicc->done, msecs_to_jiffies(timeout)))
+		return -ETIMEDOUT;
+
+	return 0;
 }
 
 static int meson_spicc_prepare_message(struct spi_master *master,
@@ -743,6 +761,8 @@ static int meson_spicc_probe(struct platform_device *pdev)
 	spicc->pdev = pdev;
 	platform_set_drvdata(pdev, spicc);
 
+	init_completion(&spicc->done);
+
 	spicc->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(spicc->base)) {
 		dev_err(&pdev->dev, "io resource mapping failed\n");

---
base-commit: 247f34f7b80357943234f93f247a1ae6b6c3a740
change-id: 20221026-spicc-burst-delay-ea0526602760

Best regards,
-- 
Neil Armstrong <neil.armstrong@...aro.org>