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Message-ID: <20230906132735.748174-1-valentin.caron@foss.st.com>
Date: Wed, 6 Sep 2023 15:27:35 +0200
From: Valentin Caron <valentin.caron@...s.st.com>
To: Mark Brown <broonie@...nel.org>
CC: Alain Volmat <alain.volmat@...s.st.com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
<linux-spi@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>,
Valentin Caron <valentin.caron@...s.st.com>
Subject: [PATCH] spi: stm32: add a delay before SPI disable
As explained in errata sheet, in section "2.14.5 Truncation of SPI output
signals after EOT event":
On STM32MP1x, EOT interrupt can be thrown before the true end of
communication.
So we add a delay of a half period to wait the real end of the
transmission.
Link: https://www.st.com/resource/en/errata_sheet/es0539-stm32mp131x3x5x-device-errata-stmicroelectronics.pdf
Signed-off-by: Valentin Caron <valentin.caron@...s.st.com>
---
drivers/spi/spi-stm32.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index b6d66caba4c0..ef665f470c5b 100644
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -277,6 +277,7 @@ struct stm32_spi_cfg {
* @fifo_size: size of the embedded fifo in bytes
* @cur_midi: master inter-data idleness in ns
* @cur_speed: speed configured in Hz
+ * @cur_half_period: time of a half bit in us
* @cur_bpw: number of bits in a single SPI data frame
* @cur_fthlv: fifo threshold level (data frames in a single data packet)
* @cur_comm: SPI communication mode
@@ -304,6 +305,7 @@ struct stm32_spi {
unsigned int cur_midi;
unsigned int cur_speed;
+ unsigned int cur_half_period;
unsigned int cur_bpw;
unsigned int cur_fthlv;
unsigned int cur_comm;
@@ -468,6 +470,8 @@ static int stm32_spi_prepare_mbr(struct stm32_spi *spi, u32 speed_hz,
spi->cur_speed = spi->clk_rate / (1 << mbrdiv);
+ spi->cur_half_period = DIV_ROUND_CLOSEST(USEC_PER_SEC, 2 * spi->cur_speed);
+
return mbrdiv - 1;
}
@@ -709,6 +713,10 @@ static void stm32h7_spi_disable(struct stm32_spi *spi)
return;
}
+ /* Add a delay to make sure that transmission is ended. */
+ if (spi->cur_half_period)
+ udelay(spi->cur_half_period);
+
if (spi->cur_usedma && spi->dma_tx)
dmaengine_terminate_async(spi->dma_tx);
if (spi->cur_usedma && spi->dma_rx)
--
2.25.1
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