drivers/i2c: Add PI7C9X2G608GP PCIe switch driver (pi608gp)

This patch adds some of the variety of configuration options exported
by the Pericom Inc. PI7C9X2G608GP PCIe switch over its SMBus interface.

Currently implemented options are only used to adjust the switch
upstream port amplitude and de-emphasis levels in millivolts. Only
values specified in the switch datasheet (in tables 6-6 and 6-8) are
allowed.

Example of a devicetree.cb entry:

	chip drivers/i2c/pi608gp
		register "gen2_3p5_enable" = "true"
		register "gen2_3p5_amp" = "AMP_LVL_MV(425)"
		register "gen2_3p5_deemph" = \
				"DEEMPH_LVL_MV(37, 5)"
		device i2c 0x6f on
			ops pi608gp_ops
		end
	end

Link to the datasheet:
https://web.archive.org/web/20210225074853/https://www.diodes.com/assets/Datasheets/PI7C9X2G608GP.pdf

BUG=none
TEST=Create devicetree.cb and Kconfig entries for this driver
in a mainboard containing the switch and verify, that the values read
out from the switch config space match the values programmed over the
SMBus.

Change-Id: Id191c4e97b99da58efd3ba38bf8cca3603ece4d5
Signed-off-by: Jan Samek <jan.samek@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74433
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/drivers/i2c/pi608gp/chip.h b/src/drivers/i2c/pi608gp/chip.h
new file mode 100644
index 0000000000..ca4a8c47ae
--- /dev/null
+++ b/src/drivers/i2c/pi608gp/chip.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __DRIVERS_I2C_PI608GP_CHIP_H__
+#define __DRIVERS_I2C_PI608GP_CHIP_H__
+
+#include "pi608gp.h"
+
+struct drivers_i2c_pi608gp_config {
+	bool gen2_3p5_enable;
+	uint32_t gen2_3p5_amp;
+	struct deemph_lvl gen2_3p5_deemph;
+};
+
+#endif /* __DRIVERS_I2C_PI608GP_CHIP_H__ */