Commit f5b84ded authored by Thomas Kopp's avatar Thomas Kopp Committed by Marc Kleine-Budde
Browse files

can: mcp25xxfd: mcp25xxfd_probe(): add SPI clk limit related errata information 



This patch adds a reference to the recent released MCP2517FD and MCP2518FD
errata sheets and paste the explanation.

The driver already implements the proposed fix.

Signed-off-by: default avatarThomas Kopp <thomas.kopp@microchip.com>
Link: https://lore.kernel.org/r/20200925065606.358-1-thomas.kopp@microchip.com


[mkl: split into two patches, adjust subject and commit message]
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 788b83ea

drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c

+14 −5
Original line number Diff line number Diff line
@@ -2819,11 +2819,21 @@ static int mcp25xxfd_probe(struct spi_device *spi) 
		priv->devtype_data = *(struct mcp25xxfd_devtype_data *)

			spi_get_device_id(spi)->driver_data;



	/* According to the datasheet the SPI clock must be less or

	 * equal SYSCLOCK / 2.

	/* Errata Reference:

	 * mcp2517fd: DS80000789B, mcp2518fd: DS80000792C 4.

	 *

	 * The SPI can write corrupted data to the RAM at fast SPI

	 * speeds:

	 *

	 * Simultaneous activity on the CAN bus while writing data to

	 * RAM via the SPI interface, with high SCK frequency, can

	 * lead to corrupted data being written to RAM.

	 *

	 * Fix/Work Around:

	 * Ensure that FSCK is less than or equal to 0.85 *

	 * (FSYSCLK/2).

	 *

	 * It turns out, that the Controller is not stable at this

	 * rate. Known good and bad combinations are:

	 * Known good and bad combinations are:

	 *

	 * MCP	ext-clk	SoC			SPI			SPI-clk		max-clk	parent-clk	Status	config

	 *
@@ -2836,7 +2846,6 @@ static int mcp25xxfd_probe(struct spi_device *spi) 
	 * 2517 40 MHz	atmel,sama5d27		atmel,at91rm9200-spi	16400000 Hz	 82.00%	 82000000 Hz	good	default

	 * 2518 40 MHz	atmel,sama5d27		atmel,at91rm9200-spi	16400000 Hz	 82.00%	 82000000 Hz	good	default

	 *

	 * Limit SPI clock to 85% of SYSCLOCK / 2 for now.

	 */

	priv->spi_max_speed_hz_orig = spi->max_speed_hz;

	spi->max_speed_hz = min(spi->max_speed_hz, freq / 2 / 1000 * 850);