[PATCH net 4/4] can: m_can: pci: use custom bit timings for Elkhart Lake

[Matthias Schiffer]

The relevant datasheet [1] specifies nonstandard limits for the bit timing
parameters. While it is unclear what the exact effect of violating these
limits is, it seems like a good idea to adhere to the documentation.

[1] Intel Atom® x6000E Series, and Intel® Pentium® and Celeron® N and J
    Series Processors for IoT Applications Datasheet,
    Volume 2 (Book 3 of 3), July 2021, Revision 001

Fixes: cab7ffc0324f ("can: m_can: add PCI glue driver for Intel Elkhart Lake")
Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
---
 drivers/net/can/m_can/m_can_pci.c | 48 ++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/m_can/m_can_pci.c b/drivers/net/can/m_can/m_can_pci.c
index d3c030a13cbe..8bbbaa264f0d 100644
--- a/drivers/net/can/m_can/m_can_pci.c
+++ b/drivers/net/can/m_can/m_can_pci.c
@@ -18,9 +18,14 @@
 
 #define M_CAN_PCI_MMIO_BAR		0
 
-#define M_CAN_CLOCK_FREQ_EHL		200000000
 #define CTL_CSR_INT_CTL_OFFSET		0x508
 
+struct m_can_pci_config {
+	const struct can_bittiming_const *bit_timing;
+	const struct can_bittiming_const *data_timing;
+	unsigned int clock_freq;
+};
+
 struct m_can_pci_priv {
 	struct m_can_classdev cdev;
 
@@ -74,9 +79,40 @@ static struct m_can_ops m_can_pci_ops = {
 	.read_fifo = iomap_read_fifo,
 };
 
+static const struct can_bittiming_const m_can_bittiming_const_ehl = {
+	.name = KBUILD_MODNAME,
+	.tseg1_min = 2,		/* Time segment 1 = prop_seg + phase_seg1 */
+	.tseg1_max = 64,
+	.tseg2_min = 1,		/* Time segment 2 = phase_seg2 */
+	.tseg2_max = 128,
+	.sjw_max = 128,
+	.brp_min = 1,
+	.brp_max = 512,
+	.brp_inc = 1,
+};
+
+static const struct can_bittiming_const m_can_data_bittiming_const_ehl = {
+	.name = KBUILD_MODNAME,
+	.tseg1_min = 2,		/* Time segment 1 = prop_seg + phase_seg1 */
+	.tseg1_max = 16,
+	.tseg2_min = 1,		/* Time segment 2 = phase_seg2 */
+	.tseg2_max = 8,
+	.sjw_max = 4,
+	.brp_min = 1,
+	.brp_max = 32,
+	.brp_inc = 1,
+};
+
+static const struct m_can_pci_config m_can_pci_ehl = {
+	.bit_timing = &m_can_bittiming_const_ehl,
+	.data_timing = &m_can_data_bittiming_const_ehl,
+	.clock_freq = 200000000,
+};
+
 static int m_can_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
 {
 	struct device *dev = &pci->dev;
+	const struct m_can_pci_config *cfg;
 	struct m_can_classdev *mcan_class;
 	struct m_can_pci_priv *priv;
 	void __iomem *base;
@@ -104,6 +140,8 @@ static int m_can_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
 	if (!mcan_class)
 		return -ENOMEM;
 
+	cfg = (const struct m_can_pci_config *)id->driver_data;
+
 	priv = cdev_to_priv(mcan_class);
 
 	priv->base = base;
@@ -115,7 +153,9 @@ static int m_can_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
 	mcan_class->dev = &pci->dev;
 	mcan_class->net->irq = pci_irq_vector(pci, 0);
 	mcan_class->pm_clock_support = 1;
-	mcan_class->can.clock.freq = id->driver_data;
+	mcan_class->bit_timing = cfg->bit_timing;
+	mcan_class->data_timing = cfg->data_timing;
+	mcan_class->can.clock.freq = cfg->clock_freq;
 	mcan_class->ops = &m_can_pci_ops;
 
 	pci_set_drvdata(pci, mcan_class);
@@ -168,8 +208,8 @@ static SIMPLE_DEV_PM_OPS(m_can_pci_pm_ops,
 			 m_can_pci_suspend, m_can_pci_resume);
 
 static const struct pci_device_id m_can_pci_id_table[] = {
-	{ PCI_VDEVICE(INTEL, 0x4bc1), M_CAN_CLOCK_FREQ_EHL, },
-	{ PCI_VDEVICE(INTEL, 0x4bc2), M_CAN_CLOCK_FREQ_EHL, },
+	{ PCI_VDEVICE(INTEL, 0x4bc1), (kernel_ulong_t)&m_can_pci_ehl, },
+	{ PCI_VDEVICE(INTEL, 0x4bc2), (kernel_ulong_t)&m_can_pci_ehl, },
 	{  }	/* Terminating Entry */
 };
 MODULE_DEVICE_TABLE(pci, m_can_pci_id_table);
-- 
2.17.1