Re: [PATCH] spi: add STM32 SPI controller driver

[Antony Pavlov <antonynpavlov@gmail.com>]

On Fri,  5 Nov 2021 08:46:57 +0100
Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:

> Tested on a STM32MP1 communicating with a ksz9563.

...

> diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
> new file mode 100644
> index 000000000000..0cb04a968c8a
> --- /dev/null
> +++ b/drivers/spi/stm32_spi.c
> @@ -0,0 +1,590 @@
> +// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
> +/*
> + * Copyright (C) 2019, STMicroelectronics - All Rights Reserved
> + *
> + * Driver for STMicroelectronics Serial peripheral interface (SPI)
> + */
> +

...

> +/* STM32_SPI_CR2 bit fields */
> +#define SPI_CR2_TSIZE		GENMASK(15, 0)

So SPI_CR2_TSIZE is (64K - 1)

...

> +
> +static int stm32_spi_transfer_one(struct stm32_spi_priv *priv,
> +				  struct spi_transfer *t)
> +{
> +	struct device_d *dev = priv->master.dev;
> +	u32 sr;
> +	u32 ifcr = 0;
> +	u32 mode;
> +	int xfer_status = 0;
> +
> +	if (t->len <= SPI_CR2_TSIZE)
> +		writel(t->len, priv->base + STM32_SPI_CR2);
> +	else
> +		return -EMSGSIZE;

So stm32_spi_transfer_one() can transfer no more than (64K - 1).
At the other hand imd tends to read more than  (64K - 1) from SPI flash, e.g.

  barebox:/ imd /dev/m25p0
  imd: error 90

Here is my solution for handling SPI flash by stm32 SPI driver (not tested on stm32):

+#include <linux/spi/spi-mem.h>
+
+static int stm32_spi_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
+{
+	if (op->data.nbytes > SPI_CR2_TSIZE) {
+		op->data.nbytes = SPI_CR2_TSIZE;
+	}
+
+	return 0;
+}
+
+static int stm32_spi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
+{
+	return -ENOTSUPP;
+}
+
+static const struct spi_controller_mem_ops stm32_spi_mem_ops = {
+	.adjust_op_size = stm32_spi_adjust_op_size,
+	.exec_op = stm32_spi_exec_op,
+};
+

...

@@ static int stm32_spi_probe(struct device_d *dev)

...

	master->setup = stm32_spi_setup;
	master->transfer = stm32_spi_transfer;
+	master->mem_ops = &stm32_spi_mem_ops;
	master->bus_num = -1;
	stm32_spi_dt_probe(priv);

-- 
Best regards,
  Antony Pavlov

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