linux-kernel - [PATCH] Module argument to control whether intel-spi-pci attempts to turn the SPI flash chip writeable

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Date:   Fri, 24 Jul 2020 18:28:53 -0300
From:   Daniel Gutson <daniel.gutson@...ypsium.com>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Daniel Gutson <daniel.gutson@...ypsium.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alex Bazhaniuk <alex@...ypsium.com>,
        Richard Hughes <hughsient@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH] Module argument to control whether intel-spi-pci attempts to turn the SPI flash chip writeable

Currently, intel-spi has a module argument that controls whether the driver
attempts to turn the SPI flash chip writeable. The default value
is FALSE (don't try to make it writeable).
However, this flag applies only for a number of devices, coming from the
platform driver, whereas the devices detected through the PCI driver
(intel-spi-pci) are not subject to this check since the configuration
takes place in intel-spi-pci which doesn't have an argument.

That's why I propose this patch to add such argument to intel-spi-pci,
so the user can control whether the driver tries to make the chip
writeable or not, being the default FALSE as is the argument of
intel-spi.

Signed-off-by: Daniel Gutson <daniel.gutson@...ypsium.com>
---
 drivers/mtd/spi-nor/controllers/intel-spi-pci.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
index 81329f680bec..77e57450f166 100644
--- a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
+++ b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
@@ -24,6 +24,10 @@ static const struct intel_spi_boardinfo cnl_info = {
 	.type = INTEL_SPI_CNL,
 };
 
+static bool writeable;
+module_param(writeable, bool, 0);
+MODULE_PARM_DESC(writeable, "Enable write access to SPI flash chip (default=0)");
+
 static int intel_spi_pci_probe(struct pci_dev *pdev,
 			       const struct pci_device_id *id)
 {
@@ -41,12 +45,14 @@ static int intel_spi_pci_probe(struct pci_dev *pdev,
 	if (!info)
 		return -ENOMEM;
 
-	/* Try to make the chip read/write */
-	pci_read_config_dword(pdev, BCR, &bcr);
-	if (!(bcr & BCR_WPD)) {
-		bcr |= BCR_WPD;
-		pci_write_config_dword(pdev, BCR, bcr);
+	if (writeable) {
+		/* Try to make the chip read/write */
 		pci_read_config_dword(pdev, BCR, &bcr);
+		if (!(bcr & BCR_WPD)) {
+			bcr |= BCR_WPD;
+			pci_write_config_dword(pdev, BCR, bcr);
+			pci_read_config_dword(pdev, BCR, &bcr);
+		}
 	}
 	info->writeable = !!(bcr & BCR_WPD);
 
-- 
2.25.1