From: Thomas Kopp <thomas.kopp@xxxxxxxxxxxxx> 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: Thomas Kopp <thomas.kopp@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200925065606.358-1-thomas.kopp@xxxxxxxxxxxxx [mkl: split into two patches, adjust subject and commit message] Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> --- .../net/can/spi/mcp25xxfd/mcp25xxfd-core.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c b/drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c index 106dda8e5310..c094bb716256 100644 --- a/drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c +++ b/drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c @@ -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); -- 2.28.0
