From 1d78f72cb5a387922870e2a54228be25f84f95f6 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Tue, 16 Jun 2020 10:23:29 +0100
Subject: [PATCH] Revert "spi: spi-bcm2835: Disable forced software
 CS"

This reverts commit 2697f0186db346176832b8eb79adaf5c874681e8.

See: https://github.com/raspberrypi/linux/pull/3687
---
 drivers/spi/spi-bcm2835.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1241,6 +1241,43 @@ static int bcm2835_spi_setup(struct spi_
 		return -EINVAL;
 	}
 
+	/*
+	 * Translate native CS to GPIO
+	 *
+	 * FIXME: poking around in the gpiolib internals like this is
+	 * not very good practice. Find a way to locate the real problem
+	 * and fix it. Why is the GPIO descriptor in spi->cs_gpiod
+	 * sometimes not assigned correctly? Erroneous device trees?
+	 */
+
+	/* get the gpio chip for the base */
+	chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
+	if (!chip)
+		return 0;
+
+	/*
+	 * Retrieve the corresponding GPIO line used for CS.
+	 * The inversion semantics will be handled by the GPIO core
+	 * code, so we pass GPIOS_OUT_LOW for "unasserted" and
+	 * the correct flag for inversion semantics. The SPI_CS_HIGH
+	 * on spi->mode cannot be checked for polarity in this case
+	 * as the flag use_gpio_descriptors enforces SPI_CS_HIGH.
+	 */
+	if (of_property_read_bool(spi->dev.of_node, "spi-cs-high"))
+		lflags = GPIO_ACTIVE_HIGH;
+	else
+		lflags = GPIO_ACTIVE_LOW;
+	spi->cs_gpiod = gpiochip_request_own_desc(chip, 8 - spi->chip_select,
+						  DRV_NAME,
+						  lflags,
+						  GPIOD_OUT_LOW);
+	if (IS_ERR(spi->cs_gpiod))
+		return PTR_ERR(spi->cs_gpiod);
+
+	/* and set up the "mode" and level */
+	dev_info(&spi->dev, "setting up native-CS%i to use GPIO\n",
+		 spi->chip_select);
+
 	return 0;
 }