[PATCH v2 2/2] mtd: spi-nor: Rework hwcaps selection for the spi-mem case

[Vignesh Raghavendra <vigneshr@xxxxxx>]

From: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>

The spi-mem layer provides a spi_mem_supports_op() function to check
whether a specific operation is supported by the controller or not.
This is much more accurate than the hwcaps selection logic based on
SPI_{RX,TX}_ flags.

Rework the hwcaps selection logic to use spi_mem_supports_op() when
nor->spimem != NULL.

Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
---
v2:
Refractor spi_nor_spimem_adjust_hwcaps to avoid looping twice over
WCAPS
Add docs to new functions
Rework spi_nor_spimem_check_op() logic

 drivers/mtd/spi-nor/spi-nor.c | 183 +++++++++++++++++++++++++++-------
 include/linux/mtd/spi-nor.h   |  14 +++
 2 files changed, 161 insertions(+), 36 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index f428a6d4022b..924dbaf3fa49 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -3028,6 +3028,129 @@ static int spi_nor_read_sfdp(struct spi_nor *nor, u32 addr,
 	return ret;
 }
 
+/**
+ * spi_nor_spimem_check_op - check if the operation is supported
+ *                           by controller
+ *@nor:        pointer to a 'struct spi_nor'
+ *@op:         pointer to op template to be checked
+ *
+ * Returns 0 if operation is supported, -ENOTSUPP otherwise.
+ */
+static int spi_nor_spimem_check_op(struct spi_nor *nor,
+				   struct spi_mem_op *op)
+{
+	/*
+	 * First test with 4 address bytes. The opcode itself might
+	 * be a 3B addressing opcode but we don't care, because
+	 * SPI controller implementation should not check the opcode,
+	 * but just the sequence.
+	 */
+	op->addr.nbytes = 4;
+	if (!spi_mem_supports_op(nor->spimem, op)) {
+		/* If flash size <16MB, 3 address bytes are sufficient */
+		if (nor->mtd.size <= SZ_16M) {
+			op->addr.nbytes = 3;
+			if (!spi_mem_supports_op(nor->spimem, op))
+				return -ENOTSUPP;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * spi_nor_spimem_check_readop - check if the read op is supported
+ *                               by controller
+ *@nor:         pointer to a 'struct spi_nor'
+ *@read:        pointer to op template to be checked
+ *
+ * Returns 0 if operation is supported, -ENOTSUPP otherwise.
+ */
+static int spi_nor_spimem_check_readop(struct spi_nor *nor,
+				       const struct spi_nor_read_command *read)
+{
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(read->opcode, 1),
+					  SPI_MEM_OP_ADDR(3, 0, 1),
+					  SPI_MEM_OP_DUMMY(0, 1),
+					  SPI_MEM_OP_DATA_IN(0, NULL, 1));
+
+	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(read->proto);
+	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(read->proto);
+	op.data.buswidth = spi_nor_get_protocol_data_nbits(read->proto);
+	op.dummy.buswidth = op.addr.buswidth;
+	op.dummy.nbytes = (read->num_mode_clocks + read->num_wait_states) *
+			  op.dummy.buswidth / 8;
+
+	return spi_nor_spimem_check_op(nor, &op);
+}
+
+/**
+ * spi_nor_spimem_check_pp - check if the page program op is supported
+ *                           by controller
+ *@nor:         pointer to a 'struct spi_nor'
+ *@pp:          pointer to op template to be checked
+ *
+ * Returns 0 if operation is supported, -ENOTSUPP otherwise.
+ */
+static int spi_nor_spimem_check_pp(struct spi_nor *nor,
+				   const struct spi_nor_pp_command *pp)
+{
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(pp->opcode, 1),
+					  SPI_MEM_OP_ADDR(3, 0, 1),
+					  SPI_MEM_OP_NO_DUMMY,
+					  SPI_MEM_OP_DATA_OUT(0, NULL, 1));
+
+	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(pp->proto);
+	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(pp->proto);
+	op.data.buswidth = spi_nor_get_protocol_data_nbits(pp->proto);
+
+	return spi_nor_spimem_check_op(nor, &op);
+}
+
+/**
+ * spi_nor_spimem_adjust_hwcaps - Find optimal Read/Write protocol
+ *                                based on SPI controller capabilities
+ * @nor:        pointer to a 'struct spi_nor'
+ * @params:     pointer to the 'struct spi_nor_flash_parameter'
+ *              representing SPI NOR flash capabilities
+ * @hwcaps:     pointer to resulting capabilities after adjusting
+ *              according to controller and flash's capability
+ */
+static void
+spi_nor_spimem_adjust_hwcaps(struct spi_nor *nor,
+			     const struct spi_nor_flash_parameter *params,
+			     u32 *hwcaps)
+{
+	unsigned int cap;
+
+	/* DTR modes are not supported yet, mask them all. */
+	*hwcaps &= ~SNOR_HWCAPS_DTR;
+
+	/* X-X-X modes are not supported yet, mask them all. */
+	*hwcaps &= ~SNOR_HWCAPS_X_X_X;
+
+	/* Start with read commands. */
+	for (cap = 0; cap < sizeof(*hwcaps) * BITS_PER_BYTE; cap++) {
+		int rdidx, ppidx;
+
+		if (!(*hwcaps & BIT(cap)))
+			continue;
+
+		rdidx = spi_nor_hwcaps_read2cmd(BIT(cap));
+		if (rdidx >= 0 &&
+		    spi_nor_spimem_check_readop(nor, &params->reads[rdidx]))
+			*hwcaps &= ~BIT(cap);
+
+		ppidx = spi_nor_hwcaps_pp2cmd(BIT(cap));
+		if (ppidx < 0)
+			continue;
+
+		if (spi_nor_spimem_check_pp(nor,
+					    &params->page_programs[ppidx]))
+			*hwcaps &= ~BIT(cap);
+	}
+}
+
 /**
  * spi_nor_read_sfdp_dma_unsafe() - read Serial Flash Discoverable Parameters.
  * @nor:	pointer to a 'struct spi_nor'
@@ -4437,16 +4560,25 @@ static int spi_nor_setup(struct spi_nor *nor,
 	 */
 	shared_mask = hwcaps->mask & params->hwcaps.mask;
 
-	/* SPI n-n-n protocols are not supported yet. */
-	ignored_mask = (SNOR_HWCAPS_READ_2_2_2 |
-			SNOR_HWCAPS_READ_4_4_4 |
-			SNOR_HWCAPS_READ_8_8_8 |
-			SNOR_HWCAPS_PP_4_4_4 |
-			SNOR_HWCAPS_PP_8_8_8);
-	if (shared_mask & ignored_mask) {
-		dev_dbg(nor->dev,
-			"SPI n-n-n protocols are not supported yet.\n");
-		shared_mask &= ~ignored_mask;
+	if (nor->spimem) {
+		/*
+		 * When called from spi_nor_probe(), all caps are set and we
+		 * need to discard some of them based on what the SPI
+		 * controller actually supports (using spi_mem_supports_op()).
+		 */
+		spi_nor_spimem_adjust_hwcaps(nor, params, &shared_mask);
+	} else {
+		/*
+		 * SPI n-n-n protocols are not supported when the SPI
+		 * controller directly implements the spi_nor interface.
+		 * Yet another reason to switch to spi-mem.
+		 */
+		ignored_mask = SNOR_HWCAPS_X_X_X;
+		if (shared_mask & ignored_mask) {
+			dev_dbg(nor->dev,
+				"SPI n-n-n protocols are not supported.\n");
+			shared_mask &= ~ignored_mask;
+		}
 	}
 
 	/* Select the (Fast) Read command. */
@@ -4775,11 +4907,11 @@ static int spi_nor_probe(struct spi_mem *spimem)
 	struct spi_device *spi = spimem->spi;
 	struct flash_platform_data *data = dev_get_platdata(&spi->dev);
 	struct spi_nor *nor;
-	struct spi_nor_hwcaps hwcaps = {
-		.mask = SNOR_HWCAPS_READ |
-			SNOR_HWCAPS_READ_FAST |
-			SNOR_HWCAPS_PP,
-	};
+	/*
+	 * Enable all caps by default. The core will mask them after
+	 * checking what's really supported using spi_mem_supports_op().
+	 */
+	const struct spi_nor_hwcaps hwcaps = { .mask = SNOR_HWCAPS_ALL };
 	char *flash_name;
 	int ret;
 
@@ -4806,27 +4938,6 @@ static int spi_nor_probe(struct spi_mem *spimem)
 
 	spi_mem_set_drvdata(spimem, nor);
 
-	if (spi->mode & SPI_RX_OCTAL) {
-		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_8;
-
-		if (spi->mode & SPI_TX_OCTAL)
-			hwcaps.mask |= (SNOR_HWCAPS_READ_1_8_8 |
-					SNOR_HWCAPS_PP_1_1_8 |
-					SNOR_HWCAPS_PP_1_8_8);
-	} else if (spi->mode & SPI_RX_QUAD) {
-		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
-
-		if (spi->mode & SPI_TX_QUAD)
-			hwcaps.mask |= (SNOR_HWCAPS_READ_1_4_4 |
-					SNOR_HWCAPS_PP_1_1_4 |
-					SNOR_HWCAPS_PP_1_4_4);
-	} else if (spi->mode & SPI_RX_DUAL) {
-		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_2;
-
-		if (spi->mode & SPI_TX_DUAL)
-			hwcaps.mask |= SNOR_HWCAPS_READ_1_2_2;
-	}
-
 	if (data && data->name)
 		nor->mtd.name = data->name;
 
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index e18c03f72ded..4521a38452d6 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -526,6 +526,20 @@ struct spi_nor_hwcaps {
 #define SNOR_HWCAPS_PP_1_8_8	BIT(21)
 #define SNOR_HWCAPS_PP_8_8_8	BIT(22)
 
+#define SNOR_HWCAPS_X_X_X	(SNOR_HWCAPS_READ_2_2_2 |	\
+				 SNOR_HWCAPS_READ_4_4_4 |	\
+				 SNOR_HWCAPS_READ_8_8_8 |	\
+				 SNOR_HWCAPS_PP_4_4_4 |		\
+				 SNOR_HWCAPS_PP_8_8_8)
+
+#define SNOR_HWCAPS_DTR		(SNOR_HWCAPS_READ_1_1_1_DTR |	\
+				 SNOR_HWCAPS_READ_1_2_2_DTR |	\
+				 SNOR_HWCAPS_READ_1_4_4_DTR |	\
+				 SNOR_HWCAPS_READ_1_8_8_DTR)
+
+#define SNOR_HWCAPS_ALL		(SNOR_HWCAPS_READ_MASK |	\
+				 SNOR_HWCAPS_PP_MASK)
+
 /**
  * spi_nor_scan() - scan the SPI NOR
  * @nor:	the spi_nor structure
-- 
2.22.0


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