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Fri, 30 Jun 2023 09:22:44 -0500 Received: from xhdakumarma40u.xilinx.com (10.180.168.240) by SATLEXMB03.amd.com (10.181.40.144) with Microsoft SMTP Server id 15.1.2507.23 via Frontend Transport; Fri, 30 Jun 2023 09:22:40 -0500 From: Amit Kumar Mahapatra To: , , , , , , , CC: , , , , , , Amit Kumar Mahapatra Subject: [PATCH v4 1/2] dt-bindings: mtd: jedec, spi-nor: Add DT property to avoid setting SRWD bit in status register Date: Fri, 30 Jun 2023 19:52:32 +0530 Message-ID: <20230630142233.63585-2-amit.kumar-mahapatra@amd.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230630142233.63585-1-amit.kumar-mahapatra@amd.com> References: <20230630142233.63585-1-amit.kumar-mahapatra@amd.com> MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6NAM11FT089:EE_|BL1PR12MB5969:EE_ X-MS-Office365-Filtering-Correlation-Id: 1b957189-6f40-4c9b-c363-08db797579b3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2023 14:22:46.2234 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1b957189-6f40-4c9b-c363-08db797579b3 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT089.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5969 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org If the WP# signal of the flash device is either not connected or is wrongly tied to GND (that includes internal pull-downs), and the software sets the status register write disable (SRWD) bit in the status register then the status register permanently becomes read-only. To avoid this added a new boolean DT property "no-wp". If this property is set in the DT then the software avoids setting the SRWD during status register write operation. Signed-off-by: Amit Kumar Mahapatra Reviewed-by: Conor Dooley Reviewed-by: Rob Herring Reviewed-by: Michael Walle --- .../devicetree/bindings/mtd/jedec,spi-nor.yaml | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml index 89959e5c47ba..97344969b02d 100644 --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml @@ -70,6 +70,21 @@ properties: be used on such systems, to denote the absence of a reliable reset mechanism. + no-wp: + type: boolean + description: + The status register write disable (SRWD) bit in status register, combined + with the WP# signal, provides hardware data protection for the device. When + the SRWD bit is set to 1, and the WP# signal is either driven LOW or hard + strapped to LOW, the status register nonvolatile bits become read-only and + the WRITE STATUS REGISTER operation will not execute. The only way to exit + this hardware-protected mode is to drive WP# HIGH. If the WP# signal of the + flash device is not connected or is wrongly tied to GND (that includes internal + pull-downs) then status register permanently becomes read-only as the SRWD bit + cannot be reset. This boolean flag can be used on such systems to avoid setting + the SRWD bit while writing the status register. WP# signal hard strapped to GND + can be a valid use case. + reset-gpios: description: A GPIO line connected to the RESET (active low) signal of the device. 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CTRY:US; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:SATLEXMB03.amd.com; PTR:InfoDomainNonexistent; CAT:NONE; SFS:(13230028)(4636009)(396003)(346002)(136003)(39860400002)(376002)(451199021)(36840700001)(46966006)(40470700004)(40460700003)(4326008)(316002)(70586007)(6666004)(478600001)(110136005)(70206006)(54906003)(36756003)(86362001)(47076005)(426003)(83380400001)(186003)(26005)(2616005)(336012)(36860700001)(82310400005)(1076003)(2906002)(5660300002)(7416002)(41300700001)(8676002)(8936002)(40480700001)(356005)(81166007)(82740400003)(36900700001); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2023 14:22:50.2076 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 928c7ed1-dc43-4f9c-b297-08db79757c13 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT107.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR12MB4882 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Setting the status register write disable (SRWD) bit in the status register (SR) with WP# signal of the flash left floating or wrongly tied to GND (that includes internal pull-downs), will configure the SR permanently as read-only. If WP# signal is left floating or wrongly tied to GND, avoid setting SRWD bit while writing the SR during flash protection. Signed-off-by: Amit Kumar Mahapatra --- drivers/mtd/spi-nor/core.c | 3 +++ drivers/mtd/spi-nor/core.h | 1 + drivers/mtd/spi-nor/debugfs.c | 1 + drivers/mtd/spi-nor/swp.c | 9 +++++++-- 4 files changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c index 0bb0ad14a2fc..520f5ab86d2b 100644 --- a/drivers/mtd/spi-nor/core.c +++ b/drivers/mtd/spi-nor/core.c @@ -2864,6 +2864,9 @@ static void spi_nor_init_flags(struct spi_nor *nor) if (flags & NO_CHIP_ERASE) nor->flags |= SNOR_F_NO_OP_CHIP_ERASE; + if (of_property_read_bool(np, "no-wp")) + nor->flags |= SNOR_F_NO_WP; + if (flags & SPI_NOR_RWW && nor->info->n_banks > 1 && !nor->controller_ops) nor->flags |= SNOR_F_RWW; diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h index 4fb5ff09c63a..55b5e7abce6e 100644 --- a/drivers/mtd/spi-nor/core.h +++ b/drivers/mtd/spi-nor/core.h @@ -132,6 +132,7 @@ enum spi_nor_option_flags { SNOR_F_SWP_IS_VOLATILE = BIT(13), SNOR_F_RWW = BIT(14), SNOR_F_ECC = BIT(15), + SNOR_F_NO_WP = BIT(16), }; struct spi_nor_read_command { diff --git a/drivers/mtd/spi-nor/debugfs.c b/drivers/mtd/spi-nor/debugfs.c index e11536fffe0f..6e163cb5b478 100644 --- a/drivers/mtd/spi-nor/debugfs.c +++ b/drivers/mtd/spi-nor/debugfs.c @@ -27,6 +27,7 @@ static const char *const snor_f_names[] = { SNOR_F_NAME(SWP_IS_VOLATILE), SNOR_F_NAME(RWW), SNOR_F_NAME(ECC), + SNOR_F_NAME(NO_WP), }; #undef SNOR_F_NAME diff --git a/drivers/mtd/spi-nor/swp.c b/drivers/mtd/spi-nor/swp.c index 0ba716e84377..5ab9d5324860 100644 --- a/drivers/mtd/spi-nor/swp.c +++ b/drivers/mtd/spi-nor/swp.c @@ -214,8 +214,13 @@ static int spi_nor_sr_lock(struct spi_nor *nor, loff_t ofs, uint64_t len) status_new = (status_old & ~mask & ~tb_mask) | val; - /* Disallow further writes if WP pin is asserted */ - status_new |= SR_SRWD; + /* + * Disallow further writes if WP# pin is neither left floating nor + * wrongly tied to GND (that includes internal pull-downs). + * WP# pin hard strapped to GND can be a valid use case. + */ + if (!(nor->flags & SNOR_F_NO_WP)) + status_new |= SR_SRWD; if (!use_top) status_new |= tb_mask;