[PATCH linux-next v4 0/5] add driver for Atmel QSPI controller

[PATCH linux-next v4 0/5] add driver for Atmel QSPI controller

[Cyrille Pitchen]

ChangeLog

v4:
- add "OF && HAS_DMA" dependency in Kconfig for Atmel Quad SPI driver.
- return -ENOMEM instead of the return code of dma_mapping_error() as this
  function returns a boolean on ARM achitecture.
- add "Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>" for Atmel Quad
  SPI driver and its DT binding documentation.

v3:
- reword the comment which explains that spi_nor_set_protocol() is used by
  the spi-nor framework to notify lower layers, especially the (Q)SPI
  controller about a protocol change.
- change the definitions of register/bitfield macros in the Atmel QSPI
  controller driver: get rid of concatenation operator and use BIT and
  GENMASK macros when possible.
- use #define[SPACE] instead of #define[TAB]

v2:
- remove the patches to set the "latency code" of Spansion QSPI memories
  (support of Spansion memories may be submitted in later series).
- rename "qspi" node into "spi" in the DT example to fit ePAPR standard.
- remove the useless "qspi0" label from the DT node example.
- remove the leading 0 from the size of the second memory region to make
  it consistent with the size of the first memory region.
- indent the DT bindings documentation to make it more readable.
- remove the useless ".bus	= &platform_bus_type," line from the
  platform driver definition.

v1:

This series of patches add support for the new Atmel QSPI controller
embedded inside sama5d2x SoCs.

These patches were first developped for linux-3.18-at91 and tested on a
sama5d27 Xplained ultra board, which embeds a Micron n25q128a13 QSPI NOR
flash memory. Then the series was adapted for mainline.

Cyrille Pitchen (5):
  mtd: spi-nor: notify (Q)SPI controller about protocol change
  Documentation: mtd: add a DT property to set the number of dummy
    cycles
  mtd: spi-nor: allow to tune the number of dummy cycles
  Documentation: atmel-quadspi: add binding file for Atmel QSPI driver
  mtd: atmel-quadspi: add driver for Atmel QSPI controller

 .../devicetree/bindings/mtd/atmel-quadspi.txt      |  29 +
 .../devicetree/bindings/mtd/jedec,spi-nor.txt      |   6 +
 drivers/mtd/spi-nor/Kconfig                        |   7 +
 drivers/mtd/spi-nor/Makefile                       |   1 +
 drivers/mtd/spi-nor/atmel-quadspi.c                | 876 +++++++++++++++++++++
 drivers/mtd/spi-nor/spi-nor.c                      | 118 ++-
 include/linux/mtd/spi-nor.h                        |  15 +
 7 files changed, 1033 insertions(+), 19 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mtd/atmel-quadspi.txt
 create mode 100644 drivers/mtd/spi-nor/atmel-quadspi.c

-- 
1.8.2.2

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[PATCH linux-next v4 1/5] mtd: spi-nor: notify (Q)SPI controller about protocol change

[Cyrille Pitchen]

Once the Quad SPI mode has been enabled on a Micron flash memory, this
device expects ALL the following commands to use the SPI 4-4-4 protocol.
The (Q)SPI controller needs to be notified about the protocol change so it
can adapt and keep on dialoging with the Micron memory.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 21 +++++++++++++++++++++
 include/linux/mtd/spi-nor.h   | 13 +++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 47df4b5eae2f..e2a6029dc056 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -163,6 +163,22 @@ static inline int write_disable(struct spi_nor *nor)
 	return nor->write_reg(nor, SPINOR_OP_WRDI, NULL, 0, 0);
 }
 
+/*
+ * Let the spi-nor framework notify lower layers, especially the driver of the
+ * (Q)SPI controller, about the new protocol to be used. Indeed, once the
+ * spi-nor framework has sent manufacturer specific commands to a memory to
+ * enable its Quad SPI mode, it should immediately after tell the QSPI
+ * controller to use the very same Quad SPI protocol as expected by the memory.
+ */
+static inline int spi_nor_set_protocol(struct spi_nor *nor,
+				       enum spi_protocol proto)
+{
+	if (nor->set_protocol)
+		return nor->set_protocol(nor, proto);
+
+	return 0;
+}
+
 static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)
 {
 	return mtd->priv;
@@ -944,6 +960,11 @@ static int micron_quad_enable(struct spi_nor *nor)
 		return ret;
 	}
 
+	/* switch protocol to Quad CMD 4-4-4 */
+	ret = spi_nor_set_protocol(nor, SPI_PROTO_4_4_4);
+	if (ret)
+		return ret;
+
 	ret = spi_nor_wait_till_ready(nor);
 	if (ret)
 		return ret;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index e5409524bb0a..1bf6f11310ef 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -87,6 +87,16 @@ enum read_mode {
 	SPI_NOR_QUAD,
 };
 
+enum spi_protocol {
+	SPI_PROTO_1_1_1,	/* SPI */
+	SPI_PROTO_1_1_2,	/* Dual Output */
+	SPI_PROTO_1_1_4,	/* Quad Output */
+	SPI_PROTO_1_2_2,	/* Dual IO */
+	SPI_PROTO_1_4_4,	/* Quad IO */
+	SPI_PROTO_2_2_2,	/* Dual Command */
+	SPI_PROTO_4_4_4,	/* Quad Command */
+};
+
 /**
  * struct spi_nor_xfer_cfg - Structure for defining a Serial Flash transfer
  * @wren:		command for "Write Enable", or 0x00 for not required
@@ -149,6 +159,7 @@ enum spi_nor_option_flags {
  *			read/write/erase/lock/unlock operations
  * @read_xfer:		[OPTIONAL] the read fundamental primitive
  * @write_xfer:		[OPTIONAL] the writefundamental primitive
+ * @set_protocol:	[OPTIONAL] notify about protocol change
  * @read_reg:		[DRIVER-SPECIFIC] read out the register
  * @write_reg:		[DRIVER-SPECIFIC] write data to the register
  * @read:		[DRIVER-SPECIFIC] read data from the SPI NOR
@@ -185,6 +196,8 @@ struct spi_nor {
 	int (*write_reg)(struct spi_nor *nor, u8 opcode, u8 *buf, int len,
 			int write_enable);
 
+	int (*set_protocol)(struct spi_nor *nor, enum spi_protocol proto);
+
 	int (*read)(struct spi_nor *nor, loff_t from,
 			size_t len, size_t *retlen, u_char *read_buf);
 	void (*write)(struct spi_nor *nor, loff_t to,
-- 
1.8.2.2

Re: [PATCH linux-next v4 1/5] mtd: spi-nor: notify (Q)SPI controller about protocol change

[Marek Vasut]

On Monday, August 24, 2015 at 12:13:56 PM, Cyrille Pitchen wrote:
> Once the Quad SPI mode has been enabled on a Micron flash memory, this
> device expects ALL the following commands to use the SPI 4-4-4 protocol.
> The (Q)SPI controller needs to be notified about the protocol change so it
> can adapt and keep on dialoging with the Micron memory.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>

Awesome,

Acked-by: Marek Vasut <marex@denx.de>

If this could be applied separately (since I want to use the same functionality
for the Cadence QSPI driver), I'd be really happy too :)

Best regards,
Marek Vasut

[PATCH linux-next v4 2/5] Documentation: mtd: add a DT property to set the number of dummy cycles

[Cyrille Pitchen]

Depending on the SPI clock frequency, the Fast Read op code and the
Single/Dual Data Rate mode, the number of dummy cycles can be tuned to
improve transfer speed.
The actual number of dummy cycles is specific for each memory model and is
provided by the manufacturer thanks to the memory datasheet.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
 Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
index 2bee68103b01..4387567d8024 100644
--- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
+++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
@@ -19,6 +19,11 @@ Optional properties:
                    all chips and support for it can not be detected at runtime.
                    Refer to your chips' datasheet to check if this is supported
                    by your chip.
+- m25p,num-dummy-cycles : Set the number of dummy cycles for Fast Read commands.
+                          Depending on the manufacturer additional dedicated
+                          commands are sent to the flash memory so the
+                          controller and the memory can agree on the number of
+                          dummy cycles to use.
 
 Example:
 
@@ -29,4 +34,5 @@ Example:
 		reg = <0>;
 		spi-max-frequency = <40000000>;
 		m25p,fast-read;
+		m25p,num-dummy-cycles = <8>;
 	};
-- 
1.8.2.2

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[PATCH linux-next v4 3/5] mtd: spi-nor: allow to tune the number of dummy cycles

[Cyrille Pitchen]

The number of dummy cycles used during Fast Read commands can be reduced
to improve transfer performances. Each manufacturer has a dedicated set of
registers to provide the memory with the exact number of dummy cycles it
should expect. Both the memory and the (Q)SPI controller must agree on
this number of dummy cycles.

The number of dummy cycles can be found into the memory datasheet and
mostly depends on the SPI clock frequency, the Fast Read op code and the
Single/Dual Data Rate mode.

Probing JEDEC Serial Flash Discoverable Parameters (SFDP) tables would
only provide the driver with a high enough number of dummy cycles for each
Fast Read command to be used for all clock frequencies: this solution
would not be optimized.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
 drivers/mtd/spi-nor/spi-nor.c | 97 ++++++++++++++++++++++++++++++++++---------
 include/linux/mtd/spi-nor.h   |  2 +
 2 files changed, 80 insertions(+), 19 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index e2a6029dc056..869e098a6841 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -119,24 +119,6 @@ static int read_cr(struct spi_nor *nor)
 }
 
 /*
- * Dummy Cycle calculation for different type of read.
- * It can be used to support more commands with
- * different dummy cycle requirements.
- */
-static inline int spi_nor_read_dummy_cycles(struct spi_nor *nor)
-{
-	switch (nor->flash_read) {
-	case SPI_NOR_FAST:
-	case SPI_NOR_DUAL:
-	case SPI_NOR_QUAD:
-		return 8;
-	case SPI_NOR_NORMAL:
-		return 0;
-	}
-	return 0;
-}
-
-/*
  * Write status register 1 byte
  * Returns negative if error occurred.
  */
@@ -1012,6 +994,81 @@ static int set_quad_mode(struct spi_nor *nor, struct flash_info *info)
 	}
 }
 
+static int micron_set_dummy_cycles(struct spi_nor *nor)
+{
+	int ret;
+	u8 val, mask;
+
+	/* read the Volatile Configuration Register (VCR) */
+	ret = nor->read_reg(nor, SPINOR_OP_RD_VCR, &val, 1);
+	if (ret < 0) {
+		dev_err(nor->dev, "error %d reading VCR\n", ret);
+		return ret;
+	}
+
+	write_enable(nor);
+
+	/* update the number of dummy into the VCR */
+	mask = GENMASK(7, 4);
+	val &= ~mask;
+	val |= (nor->read_dummy << 4) & mask;
+	ret = nor->write_reg(nor, SPINOR_OP_WR_VCR, &val, 1, 0);
+	if (ret < 0) {
+		dev_err(nor->dev, "error while writing VCR register\n");
+		return ret;
+	}
+
+	ret = spi_nor_wait_till_ready(nor);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/*
+ * Dummy Cycle calculation for different type of read.
+ * It can be used to support more commands with
+ * different dummy cycle requirements.
+ */
+static int spi_nor_read_dummy_cycles(struct spi_nor *nor,
+				     const struct flash_info *info)
+{
+	struct device_node *np = nor->dev->of_node;
+	u32 num_dummy_cycles;
+
+	if (np && !of_property_read_u32(np, "m25p,num-dummy-cycles",
+					&num_dummy_cycles)) {
+		nor->read_dummy = num_dummy_cycles;
+
+		/*
+		 * This switch block might be moved after the if...then...else
+		 * statement but it was not tested with all Spansion or Micron
+		 * memories.
+		 * Now the "m25p,num-dummy-cycles" property needs to be
+		 * explicitly set in the device tree so the switch statement is
+		 * executed. This should avoid unwanted side effects and keep
+		 * backward compatibility.
+		 */
+		switch (JEDEC_MFR(info)) {
+		case CFI_MFR_ST:
+			return micron_set_dummy_cycles(nor);
+		default:
+			break;
+		}
+	} else {
+		switch (nor->flash_read) {
+		case SPI_NOR_FAST:
+		case SPI_NOR_DUAL:
+		case SPI_NOR_QUAD:
+			nor->read_dummy = 8;
+		case SPI_NOR_NORMAL:
+			nor->read_dummy = 0;
+		}
+	}
+
+	return 0;
+}
+
 static int spi_nor_check(struct spi_nor *nor)
 {
 	if (!nor->dev || !nor->read || !nor->write ||
@@ -1216,7 +1273,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
 		nor->addr_width = 3;
 	}
 
-	nor->read_dummy = spi_nor_read_dummy_cycles(nor);
+	ret = spi_nor_read_dummy_cycles(nor, info);
+	if (ret)
+		return ret;
 
 	dev_info(dev, "%s (%lld Kbytes)\n", id->name,
 			(long long)mtd->size >> 10);
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 1bf6f11310ef..e03a4c4053d3 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -59,6 +59,8 @@
 /* Used for Micron flashes only. */
 #define SPINOR_OP_RD_EVCR      0x65    /* Read EVCR register */
 #define SPINOR_OP_WD_EVCR      0x61    /* Write EVCR register */
+#define SPINOR_OP_RD_VCR	0x85	/* Read VCR register */
+#define SPINOR_OP_WR_VCR	0x81	/* Write VCR register */
 
 /* Status Register bits. */
 #define SR_WIP			1	/* Write in progress */
-- 
1.8.2.2

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Re: [PATCH linux-next v4 3/5] mtd: spi-nor: allow to tune the number of dummy cycles

[Marek Vasut]

On Monday, August 24, 2015 at 12:13:58 PM, Cyrille Pitchen wrote:
> The number of dummy cycles used during Fast Read commands can be reduced
> to improve transfer performances. Each manufacturer has a dedicated set of
> registers to provide the memory with the exact number of dummy cycles it
> should expect. Both the memory and the (Q)SPI controller must agree on
> this number of dummy cycles.
> 
> The number of dummy cycles can be found into the memory datasheet and
> mostly depends on the SPI clock frequency, the Fast Read op code and the
> Single/Dual Data Rate mode.
> 
> Probing JEDEC Serial Flash Discoverable Parameters (SFDP) tables would
> only provide the driver with a high enough number of dummy cycles for each
> Fast Read command to be used for all clock frequencies: this solution
> would not be optimized.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>

Hi!

>  drivers/mtd/spi-nor/spi-nor.c | 97
> ++++++++++++++++++++++++++++++++++--------- include/linux/mtd/spi-nor.h  
> |  2 +
>  2 files changed, 80 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index e2a6029dc056..869e098a6841 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -119,24 +119,6 @@ static int read_cr(struct spi_nor *nor)
>  }
> 
>  /*
> - * Dummy Cycle calculation for different type of read.
> - * It can be used to support more commands with
> - * different dummy cycle requirements.
> - */
> -static inline int spi_nor_read_dummy_cycles(struct spi_nor *nor)
> -{
> -	switch (nor->flash_read) {
> -	case SPI_NOR_FAST:
> -	case SPI_NOR_DUAL:
> -	case SPI_NOR_QUAD:
> -		return 8;
> -	case SPI_NOR_NORMAL:
> -		return 0;
> -	}
> -	return 0;
> -}

You can probably just soup up this function so that it sets the
nor->read_dummy, no ?

> -/*
>   * Write status register 1 byte
>   * Returns negative if error occurred.
>   */
> @@ -1012,6 +994,81 @@ static int set_quad_mode(struct spi_nor *nor, struct
> flash_info *info) }
>  }
> 
> +static int micron_set_dummy_cycles(struct spi_nor *nor)
> +{
> +	int ret;
> +	u8 val, mask;
> +
> +	/* read the Volatile Configuration Register (VCR) */

NIT: If this is a sentence, start it with capital letter and end it with 
fullstop :)

> +	ret = nor->read_reg(nor, SPINOR_OP_RD_VCR, &val, 1);
> +	if (ret < 0) {
> +		dev_err(nor->dev, "error %d reading VCR\n", ret);
> +		return ret;
> +	}
> +
> +	write_enable(nor);
> +
> +	/* update the number of dummy into the VCR */

DTTO

> +	mask = GENMASK(7, 4);
> +	val &= ~mask;
> +	val |= (nor->read_dummy << 4) & mask;
> +	ret = nor->write_reg(nor, SPINOR_OP_WR_VCR, &val, 1, 0);
> +	if (ret < 0) {
> +		dev_err(nor->dev, "error while writing VCR register\n");
> +		return ret;
> +	}
> +
> +	ret = spi_nor_wait_till_ready(nor);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +/*
> + * Dummy Cycle calculation for different type of read.
> + * It can be used to support more commands with
> + * different dummy cycle requirements.
> + */
> +static int spi_nor_read_dummy_cycles(struct spi_nor *nor,
> +				     const struct flash_info *info)
> +{
> +	struct device_node *np = nor->dev->of_node;
> +	u32 num_dummy_cycles;
> +
> +	if (np && !of_property_read_u32(np, "m25p,num-dummy-cycles",
> +					&num_dummy_cycles)) {
> +		nor->read_dummy = num_dummy_cycles;
> +
> +		/*
> +		 * This switch block might be moved after the if...then...else
> +		 * statement but it was not tested with all Spansion or Micron
> +		 * memories.
> +		 * Now the "m25p,num-dummy-cycles" property needs to be
> +		 * explicitly set in the device tree so the switch statement is
> +		 * executed. This should avoid unwanted side effects and keep
> +		 * backward compatibility.
> +		 */
> +		switch (JEDEC_MFR(info)) {
> +		case CFI_MFR_ST:
> +			return micron_set_dummy_cycles(nor);
> +		default:

If you do have m25p,num-dummy-cycles set for non-micron flash, you have a 
problem here I believe.

> +			break;
> +		}
> +	} else {

The solution would be to drop this else {} bit here, so that if you fail in
the DT-based configuration, you fall back to this old behavior. What do you 
think please ? :)

> +		switch (nor->flash_read) {
> +		case SPI_NOR_FAST:
> +		case SPI_NOR_DUAL:
> +		case SPI_NOR_QUAD:
> +			nor->read_dummy = 8;
> +		case SPI_NOR_NORMAL:
> +			nor->read_dummy = 0;
> +		}
> +	}
> +
> +	return 0;
> +}

[...]

Re: [PATCH linux-next v4 3/5] mtd: spi-nor: allow to tune the number of dummy cycles

[Cyrille Pitchen]

Hi Marek,

Le 24/08/2015 12:48, Marek Vasut a écrit :
> On Monday, August 24, 2015 at 12:13:58 PM, Cyrille Pitchen wrote:
>> The number of dummy cycles used during Fast Read commands can be reduced
>> to improve transfer performances. Each manufacturer has a dedicated set of
>> registers to provide the memory with the exact number of dummy cycles it
>> should expect. Both the memory and the (Q)SPI controller must agree on
>> this number of dummy cycles.
>>
>> The number of dummy cycles can be found into the memory datasheet and
>> mostly depends on the SPI clock frequency, the Fast Read op code and the
>> Single/Dual Data Rate mode.
>>
>> Probing JEDEC Serial Flash Discoverable Parameters (SFDP) tables would
>> only provide the driver with a high enough number of dummy cycles for each
>> Fast Read command to be used for all clock frequencies: this solution
>> would not be optimized.
>>
>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> 
> Hi!
> 
>>  drivers/mtd/spi-nor/spi-nor.c | 97
>> ++++++++++++++++++++++++++++++++++--------- include/linux/mtd/spi-nor.h  
>> |  2 +
>>  2 files changed, 80 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index e2a6029dc056..869e098a6841 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -119,24 +119,6 @@ static int read_cr(struct spi_nor *nor)
>>  }
>>
>>  /*
>> - * Dummy Cycle calculation for different type of read.
>> - * It can be used to support more commands with
>> - * different dummy cycle requirements.
>> - */
>> -static inline int spi_nor_read_dummy_cycles(struct spi_nor *nor)
>> -{
>> -	switch (nor->flash_read) {
>> -	case SPI_NOR_FAST:
>> -	case SPI_NOR_DUAL:
>> -	case SPI_NOR_QUAD:
>> -		return 8;
>> -	case SPI_NOR_NORMAL:
>> -		return 0;
>> -	}
>> -	return 0;
>> -}
> 
> You can probably just soup up this function so that it sets the
> nor->read_dummy, no ?
>

Actually, this is what the patch does: spi_nor_read_dummy_cycles() was reused
and enhanced few lines below where you've pointed out the 
"switch (nor->flash_read)" block should be move after the else block.

I think when I wrote the code I've chosen to move the definition of this
function instead of adding forward declarations of functions such as read_cr()
or write_sr_cr(), which are now called by micron_set_dummy_cycles().

>> -/*
>>   * Write status register 1 byte
>>   * Returns negative if error occurred.
>>   */
>> @@ -1012,6 +994,81 @@ static int set_quad_mode(struct spi_nor *nor, struct
>> flash_info *info) }
>>  }
>>
>> +static int micron_set_dummy_cycles(struct spi_nor *nor)
>> +{
>> +	int ret;
>> +	u8 val, mask;
>> +
>> +	/* read the Volatile Configuration Register (VCR) */
> 
> NIT: If this is a sentence, start it with capital letter and end it with 
> fullstop :)
> 

done for the next version

>> +	ret = nor->read_reg(nor, SPINOR_OP_RD_VCR, &val, 1);
>> +	if (ret < 0) {
>> +		dev_err(nor->dev, "error %d reading VCR\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	write_enable(nor);
>> +
>> +	/* update the number of dummy into the VCR */
> 
> DTTO
> 

done for the next version

>> +	mask = GENMASK(7, 4);
>> +	val &= ~mask;
>> +	val |= (nor->read_dummy << 4) & mask;
>> +	ret = nor->write_reg(nor, SPINOR_OP_WR_VCR, &val, 1, 0);
>> +	if (ret < 0) {
>> +		dev_err(nor->dev, "error while writing VCR register\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = spi_nor_wait_till_ready(nor);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return 0;
>> +}
>> +
>> +/*
>> + * Dummy Cycle calculation for different type of read.
>> + * It can be used to support more commands with
>> + * different dummy cycle requirements.
>> + */
>> +static int spi_nor_read_dummy_cycles(struct spi_nor *nor,
>> +				     const struct flash_info *info)
>> +{
>> +	struct device_node *np = nor->dev->of_node;
>> +	u32 num_dummy_cycles;
>> +
>> +	if (np && !of_property_read_u32(np, "m25p,num-dummy-cycles",
>> +					&num_dummy_cycles)) {
>> +		nor->read_dummy = num_dummy_cycles;
>> +
>> +		/*
>> +		 * This switch block might be moved after the if...then...else
>> +		 * statement but it was not tested with all Spansion or Micron
>> +		 * memories.
>> +		 * Now the "m25p,num-dummy-cycles" property needs to be
>> +		 * explicitly set in the device tree so the switch statement is
>> +		 * executed. This should avoid unwanted side effects and keep
>> +		 * backward compatibility.
>> +		 */
>> +		switch (JEDEC_MFR(info)) {
>> +		case CFI_MFR_ST:
>> +			return micron_set_dummy_cycles(nor);
>> +		default:
> 
> If you do have m25p,num-dummy-cycles set for non-micron flash, you have a 
> problem here I believe.
> 
>> +			break;
>> +		}
>> +	} else {
> 
> The solution would be to drop this else {} bit here, so that if you fail in
> the DT-based configuration, you fall back to this old behavior. What do you 
> think please ? :)
> 

Good idea!
I also add a trace for the default case of "switch (JEDEC_MFR(info))":

dev_warn(dev, "can't set the number of dummy cycles\n");

So the user is notified that the driver could not use the value of
"m25p,num-dummy-cycles" from the DT before falling back to the legacy
code.

>> +		switch (nor->flash_read) {
>> +		case SPI_NOR_FAST:
>> +		case SPI_NOR_DUAL:
>> +		case SPI_NOR_QUAD:
>> +			nor->read_dummy = 8;
>> +		case SPI_NOR_NORMAL:
>> +			nor->read_dummy = 0;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
> 
> [...]
> 

thanks for the review!

Best regards,

Cyrille
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Re: [PATCH linux-next v4 3/5] mtd: spi-nor: allow to tune the number of dummy cycles

[Marek Vasut]

On Monday, August 24, 2015 at 06:42:46 PM, Cyrille Pitchen wrote:
> Hi Marek,

Hi!

[...]

> >> - * Dummy Cycle calculation for different type of read.
> >> - * It can be used to support more commands with
> >> - * different dummy cycle requirements.
> >> - */
> >> -static inline int spi_nor_read_dummy_cycles(struct spi_nor *nor)
> >> -{
> >> -	switch (nor->flash_read) {
> >> -	case SPI_NOR_FAST:
> >> -	case SPI_NOR_DUAL:
> >> -	case SPI_NOR_QUAD:
> >> -		return 8;
> >> -	case SPI_NOR_NORMAL:
> >> -		return 0;
> >> -	}
> >> -	return 0;
> >> -}
> > 
> > You can probably just soup up this function so that it sets the
> > nor->read_dummy, no ?
> 
> Actually, this is what the patch does: spi_nor_read_dummy_cycles() was
> reused and enhanced few lines below where you've pointed out the
> "switch (nor->flash_read)" block should be move after the else block.

You know what? I'll go get some sleep, coffee doesn't cut it anymore :)

> I think when I wrote the code I've chosen to move the definition of this
> function instead of adding forward declarations of functions such as
> read_cr() or write_sr_cr(), which are now called by
> micron_set_dummy_cycles().

Yep, that's all right, sorry for the confusion.

> >> -/*
> >> 
> >>   * Write status register 1 byte
> >>   * Returns negative if error occurred.
> >>   */
> >> 
> >> @@ -1012,6 +994,81 @@ static int set_quad_mode(struct spi_nor *nor,
> >> struct flash_info *info) }
> >> 
> >>  }

[...]

> >> +/*
> >> + * Dummy Cycle calculation for different type of read.
> >> + * It can be used to support more commands with
> >> + * different dummy cycle requirements.
> >> + */
> >> +static int spi_nor_read_dummy_cycles(struct spi_nor *nor,
> >> +				     const struct flash_info *info)
> >> +{
> >> +	struct device_node *np = nor->dev->of_node;
> >> +	u32 num_dummy_cycles;
> >> +
> >> +	if (np && !of_property_read_u32(np, "m25p,num-dummy-cycles",
> >> +					&num_dummy_cycles)) {
> >> +		nor->read_dummy = num_dummy_cycles;
> >> +
> >> +		/*
> >> +		 * This switch block might be moved after the if...then...else
> >> +		 * statement but it was not tested with all Spansion or Micron
> >> +		 * memories.
> >> +		 * Now the "m25p,num-dummy-cycles" property needs to be
> >> +		 * explicitly set in the device tree so the switch statement is
> >> +		 * executed. This should avoid unwanted side effects and keep
> >> +		 * backward compatibility.
> >> +		 */
> >> +		switch (JEDEC_MFR(info)) {
> >> +		case CFI_MFR_ST:
> >> +			return micron_set_dummy_cycles(nor);
> > 
> >> +		default:
> > If you do have m25p,num-dummy-cycles set for non-micron flash, you have a
> > problem here I believe.
> > 
> >> +			break;
> >> +		}
> >> +	} else {
> > 
> > The solution would be to drop this else {} bit here, so that if you fail
> > in the DT-based configuration, you fall back to this old behavior. What
> > do you think please ? :)
> 
> Good idea!
> I also add a trace for the default case of "switch (JEDEC_MFR(info))":
> 
> dev_warn(dev, "can't set the number of dummy cycles\n");

Maybe change this to "setting the number of dummy cycles not supported by chip, 
ignoring" or something, to be explicit about the fallback and that this is not
supported by the chip. But this is just an idea, feel free to ignore it.

> So the user is notified that the driver could not use the value of
> "m25p,num-dummy-cycles" from the DT before falling back to the legacy
> code.

Yup.

> >> +		switch (nor->flash_read) {
> >> +		case SPI_NOR_FAST:
> >> +		case SPI_NOR_DUAL:
> >> +		case SPI_NOR_QUAD:
> >> +			nor->read_dummy = 8;
> >> +		case SPI_NOR_NORMAL:
> >> +			nor->read_dummy = 0;
> >> +		}
> >> +	}
> >> +
> >> +	return 0;
> >> +}
> > 
> > [...]
> 
> thanks for the review!

Im glad it helped ;-)
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[PATCH linux-next v4 4/5] Documentation: atmel-quadspi: add binding file for Atmel QSPI driver

[Cyrille Pitchen]

This patch documents the DT bindings for the driver of the Atmel QSPI
controller embedded inside sama5d2x SoCs.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
 .../devicetree/bindings/mtd/atmel-quadspi.txt      | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/atmel-quadspi.txt

diff --git a/Documentation/devicetree/bindings/mtd/atmel-quadspi.txt b/Documentation/devicetree/bindings/mtd/atmel-quadspi.txt
new file mode 100644
index 000000000000..0b8d545bb198
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/atmel-quadspi.txt
@@ -0,0 +1,29 @@
+* Atmel Quad Serial Peripheral Interface (QSPI)
+
+Required properties:
+- compatible:     should be "atmel,sama5d2-qspi"
+- reg:            the first contains the register location and length,
+                  the second contains the memory mapping address and length
+- interrupts:     should contain the interrupt for the device
+- clocks:         the phandle of the clock needed by the QSPI controller
+- #address-cells: should be <1>
+- #size-cells:    should be <0>
+
+Example:
+
+spi@f0020000 {
+	compatible = "atmel,sama5d2-qspi";
+	reg = <0xf0020000 0x100>,
+	      <0xd0000000 0x8000000>;
+	interrupts = <52 IRQ_TYPE_LEVEL_HIGH 7>;
+	clocks = <&spi0_clk>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_spi0_default>;
+	status = "okay";
+
+	m25p80@0 {
+		...
+	};
+};
-- 
1.8.2.2

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Re: [PATCH linux-next v4 4/5] Documentation: atmel-quadspi: add binding file for Atmel QSPI driver

[Marek Vasut]

On Monday, August 24, 2015 at 12:13:59 PM, Cyrille Pitchen wrote:
> This patch documents the DT bindings for the driver of the Atmel QSPI
> controller embedded inside sama5d2x SoCs.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>

If my ack has any value in here, feel free to add it, the bindings look
pretty standard anyway:

Acked-by: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>

Best regards,
Marek Vasut
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[PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Cyrille Pitchen]

This driver add support to the new Atmel QSPI controller embedded into
sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
controller.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
 drivers/mtd/spi-nor/Kconfig         |   7 +
 drivers/mtd/spi-nor/Makefile        |   1 +
 drivers/mtd/spi-nor/atmel-quadspi.c | 876 ++++++++++++++++++++++++++++++++++++
 3 files changed, 884 insertions(+)
 create mode 100644 drivers/mtd/spi-nor/atmel-quadspi.c

diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig
index 89bf4c1faa2b..7a3d55429550 100644
--- a/drivers/mtd/spi-nor/Kconfig
+++ b/drivers/mtd/spi-nor/Kconfig
@@ -29,6 +29,13 @@ config SPI_FSL_QUADSPI
 	  This controller does not support generic SPI. It only supports
 	  SPI NOR.
 
+config SPI_ATMEL_QUADSPI
+	tristate "Atmel Quad SPI Controller"
+	depends on OF && HAS_DMA && (ARCH_AT91 || COMPILE_TEST)
+	help
+	  This enables support for the Quad SPI controller in master mode.
+	  We only connect the NOR to this controller now.
+
 config SPI_NXP_SPIFI
 	tristate "NXP SPI Flash Interface (SPIFI)"
 	depends on OF && (ARCH_LPC18XX || COMPILE_TEST)
diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile
index e53333ef8582..f5d23d7379bb 100644
--- a/drivers/mtd/spi-nor/Makefile
+++ b/drivers/mtd/spi-nor/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_MTD_SPI_NOR)	+= spi-nor.o
 obj-$(CONFIG_SPI_FSL_QUADSPI)	+= fsl-quadspi.o
+obj-$(CONFIG_SPI_ATMEL_QUADSPI)	+= atmel-quadspi.o
 obj-$(CONFIG_SPI_NXP_SPIFI)	+= nxp-spifi.o
diff --git a/drivers/mtd/spi-nor/atmel-quadspi.c b/drivers/mtd/spi-nor/atmel-quadspi.c
new file mode 100644
index 000000000000..ada6f95782e4
--- /dev/null
+++ b/drivers/mtd/spi-nor/atmel-quadspi.c
@@ -0,0 +1,876 @@
+/*
+ * Driver for Atmel QSPI Controller
+ *
+ * Copyright (C) 2015 Atmel Corporation
+ *
+ * Author: Cyrille Pitchen <cyrille.pitchen@atmel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * This driver is based on drivers/mtd/spi-nor/fsl-quadspi.c from Freescale.
+ */
+
+#include <linux/kernel.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/spi-nor.h>
+#include <linux/platform_data/atmel.h>
+#include <linux/platform_data/dma-atmel.h>
+#include <linux/of.h>
+
+#include <linux/io.h>
+#include <linux/gpio.h>
+#include <linux/pinctrl/consumer.h>
+
+/* QSPI register offsets */
+#define QSPI_CR      0x0000  /* Control Register */
+#define QSPI_MR      0x0004  /* Mode Register */
+#define QSPI_RD      0x0008  /* Receive Data Register */
+#define QSPI_TD      0x000c  /* Transmit Data Register */
+#define QSPI_SR      0x0010  /* Status Register */
+#define QSPI_IER     0x0014  /* Interrupt Enable Register */
+#define QSPI_IDR     0x0018  /* Interrupt Disable Register */
+#define QSPI_IMR     0x001c  /* Interrupt Mask Register */
+#define QSPI_SCR     0x0020  /* Serial Clock Register */
+
+#define QSPI_IAR     0x0030  /* Instruction Address Register */
+#define QSPI_ICR     0x0034  /* Instruction Code Register */
+#define QSPI_IFR     0x0038  /* Instruction Frame Register */
+
+#define QSPI_SMR     0x0040  /* Scrambling Mode Register */
+#define QSPI_SKR     0x0044  /* Scrambling Key Register */
+
+#define QSPI_WPMR    0x00E4  /* Write Protection Mode Register */
+#define QSPI_WPSR    0x00E8  /* Write Protection Status Register */
+
+#define QSPI_VERSION 0x00FC  /* Version Register */
+
+
+/* Bitfields in QSPI_CR (Control Register) */
+#define QSPI_CR_QSPIEN                  BIT(0)
+#define QSPI_CR_QSPIDIS                 BIT(1)
+#define QSPI_CR_SWRST                   BIT(7)
+#define QSPI_CR_LASTXFER                BIT(24)
+
+/* Bitfields in QSPI_MR (Mode Register) */
+#define QSPI_MR_SSM                     BIT(0)
+#define QSPI_MR_LLB                     BIT(1)
+#define QSPI_MR_WDRBT                   BIT(2)
+#define QSPI_MR_SMRM                    BIT(3)
+#define QSPI_MR_CSMODE_MASK             GENMASK(5, 4)
+#define QSPI_MR_CSMODE_NOT_RELOADED     (0 << 4)
+#define QSPI_MR_CSMODE_LASTXFER         (1 << 4)
+#define QSPI_MR_CSMODE_SYSTEMATICALLY   (2 << 4)
+#define QSPI_MR_NBBITS_MASK             GENMASK(11, 8)
+#define QSPI_MR_NBBITS(n)               ((((n) - 8) << 8) & QSPI_MR_NBBITS_MASK)
+#define QSPI_MR_DLYBCT_MASK             GENMASK(23, 16)
+#define QSPI_MR_DLYBCT(n)               (((n) << 16) & QSPI_MR_DLYBCT_MASK)
+#define QSPI_MR_DLYCS_MASK              GENMASK(31, 24)
+#define QSPI_MR_DLYCS(n)                (((n) << 24) & QSPI_MR_DLYCS_MASK)
+
+/* Bitfields in QSPI_SR/QSPI_IER/QSPI_IDR/QSPI_IMR  */
+#define QSPI_SR_RDRF                    BIT(0)
+#define QSPI_SR_TDRE                    BIT(1)
+#define QSPI_SR_TXEMPTY                 BIT(2)
+#define QSPI_SR_OVRES                   BIT(3)
+#define QSPI_SR_CSR                     BIT(8)
+#define QSPI_SR_CSS                     BIT(9)
+#define QSPI_SR_INSTRE                  BIT(10)
+#define QSPI_SR_QSPIENS                 BIT(24)
+
+/* Bitfields in QSPI_SCR (Serial Clock Register) */
+#define QSPI_SCR_CPOL                   BIT(0)
+#define QSPI_SCR_CPHA                   BIT(1)
+#define QSPI_SCR_SCBR_MASK              GENMASK(15, 8)
+#define QSPI_SCR_SCBR(n)                (((n) << 8) & QSPI_SCR_SCBR_MASK)
+#define QSPI_SCR_DLYBS_MASK             GENMASK(23, 16)
+#define QSPI_SCR_DLYBS(n)               (((n) << 16) & QSPI_SCR_DLYBS_MASK)
+
+/* Bitfields in QSPI_ICR (Instruction Code Register) */
+#define QSPI_ICR_INST_MASK              GENMASK(7, 0)
+#define QSPI_ICR_INST(inst)             (((inst) << 0) & QSPI_ICR_INST_MASK)
+#define QSPI_ICR_OPT_MASK               GENMASK(23, 16)
+#define QSPI_ICR_OPT(opt)               (((opt) << 16) & QSPI_ICR_OPT_MASK)
+
+/* Bitfields in QSPI_IFR (Instruction Frame Register) */
+#define QSPI_IFR_WIDTH_MASK             GENMASK(2, 0)
+#define QSPI_IFR_WIDTH_SINGLE_BIT_SPI   (0 << 0)
+#define QSPI_IFR_WIDTH_DUAL_OUTPUT      (1 << 0)
+#define QSPI_IFR_WIDTH_QUAD_OUTPUT      (2 << 0)
+#define QSPI_IFR_WIDTH_DUAL_IO          (3 << 0)
+#define QSPI_IFR_WIDTH_QUAD_IO          (4 << 0)
+#define QSPI_IFR_WIDTH_DUAL_CMD         (5 << 0)
+#define QSPI_IFR_WIDTH_QUAD_CMD         (6 << 0)
+#define QSPI_IFR_INSTEN                 BIT(4)
+#define QSPI_IFR_ADDREN                 BIT(5)
+#define QSPI_IFR_OPTEN                  BIT(6)
+#define QSPI_IFR_DATAEN                 BIT(7)
+#define QSPI_IFR_OPTL_MASK              GENMASK(9, 8)
+#define QSPI_IFR_OPTL_1BIT              (0 << 8)
+#define QSPI_IFR_OPTL_2BIT              (1 << 8)
+#define QSPI_IFR_OPTL_4BIT              (2 << 8)
+#define QSPI_IFR_OPTL_8BIT              (3 << 8)
+#define QSPI_IFR_ADDRL                  BIT(10)
+#define QSPI_IFR_TFRTYP_MASK            GENMASK(13, 12)
+#define QSPI_IFR_TFRTYP_TRSFR_READ      (0 << 12)
+#define QSPI_IFR_TFRTYP_TRSFR_READ_MEM  (1 << 12)
+#define QSPI_IFR_TFRTYP_TRSFR_WRITE     (2 << 12)
+#define QSPI_IFR_TFRTYP_TRSFR_WRITE_MEM (3 << 13)
+#define QSPI_IFR_CRM                    BIT(14)
+#define QSPI_IFR_NBDUM_MASK             GENMASK(20, 16)
+#define QSPI_IFR_NBDUM(n)               (((n) << 16) & QSPI_IFR_NBDUM_MASK)
+
+/* Bitfields in QSPI_SMR (Scrambling Mode Register) */
+#define QSPI_SMR_SCREN                  BIT(0)
+#define QSPI_SMR_RVDIS                  BIT(1)
+
+/* Bitfields in QSPI_WPMR (Write Protection Mode Register) */
+#define QSPI_WPMR_WPEN                  BIT(0)
+#define QSPI_WPMR_WPKEY_MASK            GENMASK(31, 8)
+#define QSPI_WPMR_WPKEY(wpkey)          (((wpkey) << 8) & QSPI_WPMR_WPKEY_MASK)
+
+/* Bitfields in QSPI_WPSR (Write Protection Status Register) */
+#define QSPI_WPSR_WPVS                  BIT(0)
+#define QSPI_WPSR_WPVSRC_MASK           GENMASK(15, 8)
+#define QSPI_WPSR_WPVSRC(src)           (((src) << 8) & QSPI_WPSR_WPVSRC)
+
+
+struct atmel_qspi {
+	void __iomem		*regs;
+	void __iomem		*mem;
+	dma_addr_t		phys_addr;
+	struct dma_chan		*chan;
+	struct clk		*clk;
+	struct platform_device	*pdev;
+	u32			ifr_width;
+	u32			pending;
+
+	struct mtd_info		mtd;
+	struct spi_nor		nor;
+	u32			clk_rate;
+	struct completion	completion;
+
+#ifdef DEBUG
+	u8			last_instruction;
+#endif
+};
+
+struct atmel_qspi_command {
+	u32	ifr_tfrtyp;
+	union {
+		struct {
+			u32	instruction:1;
+			u32	address:3;
+			u32	mode:1;
+			u32	dummy:1;
+			u32	data:1;
+			u32	dma:1;
+			u32	reserved:24;
+		}		bits;
+		u32	word;
+	}	enable;
+	u8	instruction;
+	u8	mode;
+	u8	num_mode_cycles;
+	u8	num_dummy_cycles;
+	u32	address;
+
+	size_t		buf_len;
+	const void	*tx_buf;
+	void		*rx_buf;
+};
+
+/* Register access macros */
+static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
+{
+	return readl_relaxed(aq->regs + reg);
+}
+
+static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
+{
+	writel_relaxed(value, aq->regs + reg);
+}
+
+static inline u16 qspi_readw(struct atmel_qspi *aq, u32 reg)
+{
+	return readw_relaxed(aq->regs + reg);
+}
+
+static inline void qspi_writew(struct atmel_qspi *aq, u32 reg, u16 value)
+{
+	writew_relaxed(value, aq->regs + reg);
+}
+
+static inline u8 qspi_readb(struct atmel_qspi *aq, u32 reg)
+{
+	return readb_relaxed(aq->regs + reg);
+}
+
+static inline void qspi_writeb(struct atmel_qspi *aq, u32 reg, u8 value)
+{
+	writeb_relaxed(value, aq->regs + reg);
+}
+
+
+#define QSPI_DMA_THRESHOLD	32
+
+static void atmel_qspi_dma_callback(void *arg)
+{
+	struct completion *c = arg;
+
+	complete(c);
+}
+
+static int atmel_qspi_run_dma_transfer(struct atmel_qspi *aq,
+				       const struct atmel_qspi_command *cmd)
+{
+	u32 offset = (cmd->enable.bits.address) ? cmd->address : 0;
+	struct dma_chan *chan = aq->chan;
+	struct device *dev = &aq->pdev->dev;
+	enum dma_data_direction direction;
+	dma_addr_t phys_addr, dst, src;
+	struct dma_async_tx_descriptor *desc;
+	struct completion completion;
+	dma_cookie_t cookie;
+	int err = 0;
+
+	if (cmd->tx_buf) {
+		direction = DMA_TO_DEVICE;
+		phys_addr = dma_map_single(dev, (void *)cmd->tx_buf,
+					   cmd->buf_len, direction);
+		src = phys_addr;
+		dst = aq->phys_addr + offset;
+	} else {
+		direction = DMA_FROM_DEVICE;
+		phys_addr = dma_map_single(dev, (void *)cmd->rx_buf,
+					   cmd->buf_len, direction);
+		src = aq->phys_addr + offset;
+		dst = phys_addr;
+	}
+	if (dma_mapping_error(dev, phys_addr))
+		return -ENOMEM;
+
+	desc = chan->device->device_prep_dma_memcpy(chan, dst, src,
+						    cmd->buf_len,
+						    DMA_PREP_INTERRUPT);
+	if (!desc) {
+		err = -ENOMEM;
+		goto unmap_single;
+	}
+
+	init_completion(&completion);
+	desc->callback = atmel_qspi_dma_callback;
+	desc->callback_param = &completion;
+	cookie = dmaengine_submit(desc);
+	err = dma_submit_error(cookie);
+	if (err)
+		goto unmap_single;
+	dma_async_issue_pending(chan);
+
+	if (!wait_for_completion_timeout(&completion, msecs_to_jiffies(1000)))
+		err = -ETIMEDOUT;
+
+	if (dma_async_is_tx_complete(chan, cookie, NULL, NULL) != DMA_COMPLETE)
+		err = -ETIMEDOUT;
+
+	if (err)
+		dmaengine_terminate_all(chan);
+unmap_single:
+	dma_unmap_single(dev, phys_addr, cmd->buf_len, direction);
+
+	return err;
+}
+
+static int atmel_qspi_run_transfer(struct atmel_qspi *aq,
+				   const struct atmel_qspi_command *cmd)
+{
+	void __iomem *ahb_mem;
+
+	/* First try a DMA transfer */
+	if (aq->chan && cmd->enable.bits.dma &&
+	    cmd->buf_len >= QSPI_DMA_THRESHOLD)
+		return atmel_qspi_run_dma_transfer(aq, cmd);
+
+	/* Then fallback to a PIO transfer */
+	ahb_mem = aq->mem;
+	if (cmd->enable.bits.address)
+		ahb_mem += cmd->address;
+	if (cmd->tx_buf)
+		memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
+	else
+		memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
+
+	return 0;
+}
+
+#ifdef DEBUG
+static void atmel_qspi_debug_command(struct atmel_qspi *aq,
+				     const struct atmel_qspi_command *cmd)
+{
+	u8 cmd_buf[SPI_NOR_MAX_CMD_SIZE];
+	size_t len = 0;
+	int i;
+
+	if (cmd->enable.bits.instruction) {
+		if (aq->last_instruction == cmd->instruction)
+			return;
+		aq->last_instruction = cmd->instruction;
+	}
+
+	if (cmd->enable.bits.instruction)
+		cmd_buf[len++] = cmd->instruction;
+
+	for (i = cmd->enable.bits.address-1; i >= 0; --i)
+		cmd_buf[len++] = (cmd->address >> (i << 3)) & 0xff;
+
+	if (cmd->enable.bits.mode)
+		cmd_buf[len++] = cmd->mode;
+
+	if (cmd->enable.bits.dummy) {
+		int num = cmd->num_dummy_cycles;
+
+		switch (aq->ifr_width) {
+		case QSPI_IFR_WIDTH_SINGLE_BIT_SPI:
+		case QSPI_IFR_WIDTH_DUAL_OUTPUT:
+		case QSPI_IFR_WIDTH_QUAD_OUTPUT:
+			num >>= 3;
+			break;
+		case QSPI_IFR_WIDTH_DUAL_IO:
+		case QSPI_IFR_WIDTH_DUAL_CMD:
+			num >>= 2;
+			break;
+		case QSPI_IFR_WIDTH_QUAD_IO:
+		case QSPI_IFR_WIDTH_QUAD_CMD:
+			num >>= 1;
+			break;
+		default:
+			return;
+		}
+
+		for (i = 0; i < num; ++i)
+			cmd_buf[len++] = 0;
+	}
+
+	/* Dump the SPI command */
+	print_hex_dump(KERN_DEBUG, "qspi cmd: ", DUMP_PREFIX_NONE,
+		       32, 1, cmd_buf, len, false);
+
+#ifdef VERBOSE_DEBUG
+	/* If verbose debug is enabled, also dump the TX data */
+	if (cmd->enable.bits.data && cmd->tx_buf)
+		print_hex_dump(KERN_DEBUG, "qspi tx : ", DUMP_PREFIX_NONE,
+			       32, 1, cmd->tx_buf, cmd->buf_len, false);
+#endif
+}
+#else
+#define atmel_qspi_debug_command(aq, cmd)
+#endif
+
+static int atmel_qspi_run_command(struct atmel_qspi *aq,
+				  const struct atmel_qspi_command *cmd)
+{
+	u32 iar, icr, ifr, sr;
+	int err = 0;
+
+	iar = 0;
+	icr = 0;
+	ifr = aq->ifr_width | cmd->ifr_tfrtyp;
+
+	/* Compute instruction parameters */
+	if (cmd->enable.bits.instruction) {
+		icr |= QSPI_ICR_INST(cmd->instruction);
+		ifr |= QSPI_IFR_INSTEN;
+	}
+
+	/* Compute address parameters */
+	switch (cmd->enable.bits.address) {
+	case 4:
+		ifr |= QSPI_IFR_ADDRL;
+		/*break;*/ /* fallback to the 24bit address case */
+	case 3:
+		iar = (cmd->enable.bits.data) ? 0 : cmd->address;
+		ifr |= QSPI_IFR_ADDREN;
+		break;
+	case 0:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Compute option parameters */
+	if (cmd->enable.bits.mode && cmd->num_mode_cycles) {
+		u32 mode_cycle_bits, mode_bits;
+
+		icr |= QSPI_ICR_OPT(cmd->mode);
+		ifr |= QSPI_IFR_OPTEN;
+
+		switch (ifr & QSPI_IFR_WIDTH_MASK) {
+		case QSPI_IFR_WIDTH_SINGLE_BIT_SPI:
+		case QSPI_IFR_WIDTH_DUAL_OUTPUT:
+		case QSPI_IFR_WIDTH_QUAD_OUTPUT:
+			mode_cycle_bits = 1;
+			break;
+		case QSPI_IFR_WIDTH_DUAL_IO:
+		case QSPI_IFR_WIDTH_DUAL_CMD:
+			mode_cycle_bits = 2;
+			break;
+		case QSPI_IFR_WIDTH_QUAD_IO:
+		case QSPI_IFR_WIDTH_QUAD_CMD:
+			mode_cycle_bits = 4;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		mode_bits = cmd->num_mode_cycles * mode_cycle_bits;
+		switch (mode_bits) {
+		case 1:
+			ifr |= QSPI_IFR_OPTL_1BIT;
+			break;
+
+		case 2:
+			ifr |= QSPI_IFR_OPTL_2BIT;
+			break;
+
+		case 4:
+			ifr |= QSPI_IFR_OPTL_4BIT;
+			break;
+
+		case 8:
+			ifr |= QSPI_IFR_OPTL_8BIT;
+			break;
+
+		default:
+			return -EINVAL;
+		}
+	}
+
+	/* Set number of dummy cycles */
+	if (cmd->enable.bits.dummy)
+		ifr |= QSPI_IFR_NBDUM(cmd->num_dummy_cycles);
+
+	/* Set data enable */
+	if (cmd->enable.bits.data) {
+		ifr |= QSPI_IFR_DATAEN;
+
+		/* Special case for Continuous Read Mode */
+		if (!cmd->tx_buf && !cmd->rx_buf)
+			ifr |= QSPI_IFR_CRM;
+	}
+
+	/* Set QSPI Instruction Frame registers */
+	atmel_qspi_debug_command(aq, cmd);
+	qspi_writel(aq, QSPI_IAR, iar);
+	qspi_writel(aq, QSPI_ICR, icr);
+	qspi_writel(aq, QSPI_IFR, ifr);
+
+	/* Skip to the final steps if there is no data */
+	if (!cmd->enable.bits.data)
+		goto no_data;
+
+	/* Dummy read of QSPI_IFR to synchronize APB and AHB accesses */
+	(void)qspi_readl(aq, QSPI_IFR);
+
+	/* Stop here for continuous read */
+	if (!cmd->tx_buf && !cmd->rx_buf)
+		return 0;
+	/* Send/Receive data */
+	err = atmel_qspi_run_transfer(aq, cmd);
+
+	/* Release the chip-select */
+	qspi_writel(aq, QSPI_CR, QSPI_CR_LASTXFER);
+
+	if (err)
+		return err;
+
+#if defined(DEBUG) && defined(VERBOSE_DEBUG)
+	/*
+	 * If verbose debug is enabled, also dump the RX data in addition to
+	 * the SPI command previously dumped by atmel_qspi_debug_command()
+	 */
+	if (cmd->rx_buf)
+		print_hex_dump(KERN_DEBUG, "qspi rx : ", DUMP_PREFIX_NONE,
+			       32, 1, cmd->rx_buf, cmd->buf_len, false);
+#endif
+no_data:
+	/* Poll INSTRuction End status */
+	sr = qspi_readl(aq, QSPI_SR);
+	if (sr & QSPI_SR_INSTRE)
+		return err;
+
+	/* Wait for INSTRuction End interrupt */
+	init_completion(&aq->completion);
+	aq->pending = 0;
+	qspi_writel(aq, QSPI_IER, QSPI_SR_INSTRE);
+	if (!wait_for_completion_timeout(&aq->completion,
+					 msecs_to_jiffies(1000)))
+		err = -ETIMEDOUT;
+	qspi_writel(aq, QSPI_IDR, QSPI_SR_INSTRE);
+
+	return err;
+}
+
+static int atmel_qspi_read_reg(struct spi_nor *nor, u8 opcode,
+			       u8 *buf, int len)
+{
+	struct atmel_qspi *aq = nor->priv;
+	struct atmel_qspi_command cmd;
+
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.ifr_tfrtyp = QSPI_IFR_TFRTYP_TRSFR_READ;
+	cmd.enable.bits.instruction = 1;
+	cmd.enable.bits.data = 1;
+	cmd.instruction = opcode;
+	cmd.rx_buf = buf;
+	cmd.buf_len = len;
+	return atmel_qspi_run_command(aq, &cmd);
+}
+
+static int atmel_qspi_write_reg(struct spi_nor *nor, u8 opcode,
+				u8 *buf, int len,
+				int write_enable)
+{
+	struct atmel_qspi *aq = nor->priv;
+	struct atmel_qspi_command cmd;
+
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.ifr_tfrtyp = QSPI_IFR_TFRTYP_TRSFR_WRITE;
+	cmd.enable.bits.instruction = 1;
+	cmd.enable.bits.data = (buf != NULL && len > 0);
+	cmd.instruction = opcode;
+	cmd.tx_buf = buf;
+	cmd.buf_len = len;
+	return atmel_qspi_run_command(aq, &cmd);
+}
+
+static void atmel_qspi_write(struct spi_nor *nor, loff_t to, size_t len,
+			     size_t *retlen, const u_char *write_buf)
+{
+	struct atmel_qspi *aq = nor->priv;
+	struct atmel_qspi_command cmd;
+
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.ifr_tfrtyp = QSPI_IFR_TFRTYP_TRSFR_WRITE_MEM;
+	cmd.enable.bits.instruction = 1;
+	cmd.enable.bits.address = nor->addr_width;
+	cmd.enable.bits.data = 1;
+	cmd.enable.bits.dma = 1;
+	cmd.instruction = nor->program_opcode;
+	cmd.address = (u32)to;
+	cmd.tx_buf = write_buf;
+	cmd.buf_len = len;
+	if (!atmel_qspi_run_command(aq, &cmd))
+		*retlen += len;
+}
+
+static int atmel_qspi_erase(struct spi_nor *nor, loff_t offs)
+{
+	struct atmel_qspi *aq = nor->priv;
+	struct atmel_qspi_command cmd;
+
+	dev_dbg(nor->dev, "%dKiB at 0x%08x\n",
+		aq->mtd.erasesize / 1024, (u32)offs);
+
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.ifr_tfrtyp = QSPI_IFR_TFRTYP_TRSFR_WRITE;
+	cmd.enable.bits.instruction = 1;
+	cmd.enable.bits.address = nor->addr_width;
+	cmd.instruction = nor->erase_opcode;
+	cmd.address = (u32)offs;
+	return atmel_qspi_run_command(aq, &cmd);
+}
+
+static int atmel_qspi_read(struct spi_nor *nor, loff_t from, size_t len,
+			   size_t *retlen, u_char *read_buf)
+{
+	struct atmel_qspi *aq = nor->priv;
+	struct atmel_qspi_command cmd;
+	int err;
+
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.ifr_tfrtyp = QSPI_IFR_TFRTYP_TRSFR_READ_MEM;
+	cmd.enable.bits.instruction = 1;
+	cmd.enable.bits.address = nor->addr_width;
+	cmd.enable.bits.dummy = (nor->read_dummy > 0);
+	cmd.enable.bits.data = 1;
+	cmd.enable.bits.dma = 1;
+	cmd.instruction = nor->read_opcode;
+	cmd.address = (u32)from;
+	cmd.num_dummy_cycles = nor->read_dummy;
+	cmd.rx_buf = read_buf;
+	cmd.buf_len = len;
+	err = atmel_qspi_run_command(aq, &cmd);
+	if (err)
+		return err;
+
+	*retlen += len;
+	return 0;
+}
+
+static int atmel_qspi_set_protocol(struct spi_nor *nor, enum spi_protocol proto)
+{
+	struct atmel_qspi *aq = nor->priv;
+
+	switch (proto) {
+	case SPI_PROTO_1_1_1:
+		aq->ifr_width = QSPI_IFR_WIDTH_SINGLE_BIT_SPI;
+		break;
+	case SPI_PROTO_1_1_2:
+		aq->ifr_width = QSPI_IFR_WIDTH_DUAL_OUTPUT;
+		break;
+	case SPI_PROTO_1_1_4:
+		aq->ifr_width = QSPI_IFR_WIDTH_QUAD_OUTPUT;
+		break;
+	case SPI_PROTO_1_2_2:
+		aq->ifr_width = QSPI_IFR_WIDTH_DUAL_IO;
+		break;
+	case SPI_PROTO_1_4_4:
+		aq->ifr_width = QSPI_IFR_WIDTH_QUAD_IO;
+		break;
+	case SPI_PROTO_2_2_2:
+		aq->ifr_width = QSPI_IFR_WIDTH_DUAL_CMD;
+		break;
+	case SPI_PROTO_4_4_4:
+		aq->ifr_width = QSPI_IFR_WIDTH_QUAD_CMD;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int atmel_qspi_init(struct atmel_qspi *aq)
+{
+	unsigned long src_rate;
+	u32 mr, scr, scbr;
+
+	/* Reset the QSPI controller */
+	qspi_writel(aq, QSPI_CR, QSPI_CR_SWRST);
+
+	/* Set the QSPI controller in Serial Memory Mode */
+	mr = QSPI_MR_SSM | QSPI_MR_NBBITS(8);
+	qspi_writel(aq, QSPI_MR, mr);
+
+	src_rate = clk_get_rate(aq->clk);
+	if (!src_rate)
+		return -EINVAL;
+
+	/* Compute the QSPI baudrate */
+	scbr = DIV_ROUND_UP(src_rate, aq->clk_rate);
+	if (scbr > 0)
+		scbr--;
+	scr = QSPI_SCR_SCBR(scbr);
+	qspi_writel(aq, QSPI_SCR, scr);
+
+	/* Enable the QSPI controller */
+	qspi_writel(aq, QSPI_CR, QSPI_CR_QSPIEN);
+
+	return 0;
+}
+
+static irqreturn_t atmel_qspi_interrupt(int irq, void *dev_id)
+{
+	struct atmel_qspi *aq = (struct atmel_qspi *)dev_id;
+	u32 status, mask, pending;
+
+	status = qspi_readl(aq, QSPI_SR);
+	mask = qspi_readl(aq, QSPI_IMR);
+	pending = status & mask;
+
+	if (!pending)
+		return IRQ_NONE;
+
+	aq->pending |= pending;
+	if (pending & QSPI_SR_INSTRE)
+		complete(&aq->completion);
+
+	return IRQ_HANDLED;
+}
+
+static int atmel_qspi_probe(struct platform_device *pdev)
+{
+	struct device_node *child, *np = pdev->dev.of_node;
+	struct mtd_part_parser_data ppdata;
+	struct atmel_qspi *aq;
+	struct resource *res;
+	dma_cap_mask_t mask;
+	struct spi_nor *nor;
+	struct mtd_info *mtd;
+	char modalias[40];
+	int irq, err = 0;
+
+	if (of_get_child_count(np) != 1)
+		return -ENODEV;
+	child = of_get_next_child(np, NULL);
+
+	aq = devm_kzalloc(&pdev->dev, sizeof(*aq), GFP_KERNEL);
+	if (!aq) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	platform_set_drvdata(pdev, aq);
+	aq->pdev = pdev;
+	/* Start in Extended SPI (1-1-1) */
+	aq->ifr_width = QSPI_IFR_WIDTH_SINGLE_BIT_SPI;
+
+	/* Map the registers */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	aq->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(aq->regs)) {
+		dev_err(&pdev->dev, "missing registers\n");
+		err = PTR_ERR(aq->regs);
+		goto exit;
+	}
+
+	/* Map the AHB memory */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	aq->mem = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(aq->mem)) {
+		dev_err(&pdev->dev, "missing AHB memory\n");
+		err = PTR_ERR(aq->regs);
+		goto exit;
+	}
+	aq->phys_addr = (dma_addr_t)res->start;
+
+	/* Get the peripheral clock */
+	aq->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(aq->clk)) {
+		dev_err(&pdev->dev, "missing peripheral clock\n");
+		err = PTR_ERR(aq->clk);
+		goto exit;
+	}
+
+	/* Enable the peripheral clock */
+	err = clk_prepare_enable(aq->clk);
+	if (err) {
+		dev_err(&pdev->dev, "failed to enable the peripheral clock\n");
+		goto exit;
+	}
+
+	/* Request the IRQ */
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "missing IRQ\n");
+		err = irq;
+		goto disable_clk;
+	}
+	err = devm_request_irq(&pdev->dev, irq, atmel_qspi_interrupt,
+			       0, dev_name(&pdev->dev), aq);
+	if (err)
+		goto disable_clk;
+
+	/* Try to get a DMA channel for memcpy() operation */
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_MEMCPY, mask);
+	aq->chan = dma_request_channel(mask, NULL, NULL);
+	if (!aq->chan)
+		dev_warn(&pdev->dev, "no available DMA channel\n");
+
+	/* Setup the spi-nor */
+	nor = &aq->nor;
+	mtd = &aq->mtd;
+
+	nor->mtd = mtd;
+	nor->dev = &pdev->dev;
+	nor->priv = aq;
+	mtd->priv = nor;
+
+	nor->read_reg = atmel_qspi_read_reg;
+	nor->write_reg = atmel_qspi_write_reg;
+	nor->read = atmel_qspi_read;
+	nor->write = atmel_qspi_write;
+	nor->erase = atmel_qspi_erase;
+	nor->set_protocol = atmel_qspi_set_protocol;
+
+	if (of_modalias_node(child, modalias, sizeof(modalias)) < 0) {
+		err = -ENODEV;
+		goto release_channel;
+	}
+
+	err = of_property_read_u32(child, "spi-max-frequency", &aq->clk_rate);
+	if (err < 0)
+		goto release_channel;
+
+	err = atmel_qspi_init(aq);
+	if (err)
+		goto release_channel;
+
+	nor->dev->of_node = child;
+	err = spi_nor_scan(nor, modalias, SPI_NOR_QUAD);
+	nor->dev->of_node = np;
+	if (err)
+		goto release_channel;
+
+	ppdata.of_node = child;
+	err = mtd_device_parse_register(mtd, NULL, &ppdata, NULL, 0);
+	if (err)
+		goto release_channel;
+
+	of_node_put(child);
+
+	return 0;
+
+release_channel:
+	if (aq->chan)
+		dma_release_channel(aq->chan);
+disable_clk:
+	clk_disable_unprepare(aq->clk);
+exit:
+	of_node_put(child);
+
+	return err;
+}
+
+static int atmel_qspi_remove(struct platform_device *pdev)
+{
+	struct atmel_qspi *aq = platform_get_drvdata(pdev);
+
+	mtd_device_unregister(&aq->mtd);
+	qspi_writel(aq, QSPI_CR, QSPI_CR_QSPIDIS);
+	if (aq->chan)
+		dma_release_channel(aq->chan);
+	clk_disable_unprepare(aq->clk);
+	return 0;
+}
+
+
+static const struct of_device_id atmel_qspi_dt_ids[] = {
+	{ .compatible = "atmel,sama5d2-qspi" },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, atmel_qspi_dt_ids);
+
+static struct platform_driver atmel_qspi_driver = {
+	.driver = {
+		.name	= "atmel_qspi",
+		.of_match_table	= atmel_qspi_dt_ids,
+	},
+	.probe		= atmel_qspi_probe,
+	.remove		= atmel_qspi_remove,
+};
+module_platform_driver(atmel_qspi_driver);
+
+MODULE_AUTHOR("Cyrille Pitchen <cyrille.pitchen@atmel.com>");
+MODULE_DESCRIPTION("Atmel QSPI Controller driver");
+MODULE_LICENSE("GPL v2");
-- 
1.8.2.2

Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Marek Vasut]

On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
> This driver add support to the new Atmel QSPI controller embedded into
> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
> controller.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>

Hi,

[...]

> +/* Register access macros */

These are functions, not macros :)

btw is there any reason for these ? I'd say, just put the read*() and
write*() functions directly into the code and be done with it, it is
much less confusing.

Also, why do you use the _relaxed() versions of the functions ?

> +static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
> +{
> +	return readl_relaxed(aq->regs + reg);
> +}
> +
> +static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
> +{
> +	writel_relaxed(value, aq->regs + reg);
> +}
> +
> +static inline u16 qspi_readw(struct atmel_qspi *aq, u32 reg)
> +{
> +	return readw_relaxed(aq->regs + reg);
> +}
> +
> +static inline void qspi_writew(struct atmel_qspi *aq, u32 reg, u16 value)
> +{
> +	writew_relaxed(value, aq->regs + reg);
> +}
> +
> +static inline u8 qspi_readb(struct atmel_qspi *aq, u32 reg)
> +{
> +	return readb_relaxed(aq->regs + reg);
> +}
> +
> +static inline void qspi_writeb(struct atmel_qspi *aq, u32 reg, u8 value)
> +{
> +	writeb_relaxed(value, aq->regs + reg);
> +}

[...]

> +static int atmel_qspi_run_command(struct atmel_qspi *aq,
> +				  const struct atmel_qspi_command *cmd)
> +{
> +	u32 iar, icr, ifr, sr;
> +	int err = 0;
> +
> +	iar = 0;
> +	icr = 0;
> +	ifr = aq->ifr_width | cmd->ifr_tfrtyp;
> +
> +	/* Compute instruction parameters */
> +	if (cmd->enable.bits.instruction) {
> +		icr |= QSPI_ICR_INST(cmd->instruction);
> +		ifr |= QSPI_IFR_INSTEN;
> +	}
> +
> +	/* Compute address parameters */
> +	switch (cmd->enable.bits.address) {
> +	case 4:
> +		ifr |= QSPI_IFR_ADDRL;
> +		/*break;*/ /* fallback to the 24bit address case */

What's this commented out bit of code for ? :-)

> +	case 3:
> +		iar = (cmd->enable.bits.data) ? 0 : cmd->address;
> +		ifr |= QSPI_IFR_ADDREN;
> +		break;
> +	case 0:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}

[...]

> +no_data:
> +	/* Poll INSTRuction End status */
> +	sr = qspi_readl(aq, QSPI_SR);
> +	if (sr & QSPI_SR_INSTRE)
> +		return err;
> +
> +	/* Wait for INSTRuction End interrupt */
> +	init_completion(&aq->completion);

You should use reinit_completion() in the code. init_completion()
should be used only in the probe() function and nowhere else.

> +	aq->pending = 0;
> +	qspi_writel(aq, QSPI_IER, QSPI_SR_INSTRE);
> +	if (!wait_for_completion_timeout(&aq->completion,
> +					 msecs_to_jiffies(1000)))
> +		err = -ETIMEDOUT;
> +	qspi_writel(aq, QSPI_IDR, QSPI_SR_INSTRE);
> +
> +	return err;
> +}

[...]

Hope this helps :)
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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Russell King - ARM Linux]

On Mon, Aug 24, 2015 at 01:03:51PM +0200, Marek Vasut wrote:
> These are functions, not macros :)
> 
> btw is there any reason for these ? I'd say, just put the read*() and
> write*() functions directly into the code and be done with it, it is
> much less confusing.
> 
> Also, why do you use the _relaxed() versions of the functions ?

Now that the _relaxed() accessors are available throughout the kernel,
everyone should be using the _relaxed() versions unless they need the
properties of the non-relaxed versions.  Remember that the non-relaxed
versions are rather expensive on ARM due to the need to go all the way
out to the L2 cache - it at least doubles the number of accesses for
every read*/write*().

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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Marek Vasut]

On Monday, August 24, 2015 at 02:49:24 PM, Russell King - ARM Linux wrote:

Hi Russell,

> On Mon, Aug 24, 2015 at 01:03:51PM +0200, Marek Vasut wrote:
> > These are functions, not macros :)
> > 
> > btw is there any reason for these ? I'd say, just put the read*() and
> > write*() functions directly into the code and be done with it, it is
> > much less confusing.
> > 
> > Also, why do you use the _relaxed() versions of the functions ?
> 
> Now that the _relaxed() accessors are available throughout the kernel,
> everyone should be using the _relaxed() versions unless they need the
> properties of the non-relaxed versions.

You mean the memory barrier, right ?

> Remember that the non-relaxed
> versions are rather expensive on ARM due to the need to go all the way
> out to the L2 cache - it at least doubles the number of accesses for
> every read*/write*().

I think in case of this driver, we don't need the non-relaxed version
anywhere, right ? Thanks for the educational writeup :)

btw. is [1] still the current study material on the I/O accessor best
practices please ?

[1] http://permalink.gmane.org/gmane.linux.ports.arm.kernel/117644

Best regards,
Marek Vasut

Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Cyrille Pitchen]

Hi Marek,

Le 24/08/2015 13:03, Marek Vasut a écrit :
> On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
>> This driver add support to the new Atmel QSPI controller embedded into
>> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
>> controller.
>>
>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> 
> Hi,
> 
> [...]
> 
>> +/* Register access macros */
> 
> These are functions, not macros :)
> 
> btw is there any reason for these ? I'd say, just put the read*() and
> write*() functions directly into the code and be done with it, it is
> much less confusing.
> 
> Also, why do you use the _relaxed() versions of the functions ?
> 
>> +static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readl_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
>> +{
>> +	writel_relaxed(value, aq->regs + reg);
>> +}
>> +
>> +static inline u16 qspi_readw(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readw_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writew(struct atmel_qspi *aq, u32 reg, u16 value)
>> +{
>> +	writew_relaxed(value, aq->regs + reg);
>> +}
>> +
>> +static inline u8 qspi_readb(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readb_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writeb(struct atmel_qspi *aq, u32 reg, u8 value)
>> +{
>> +	writeb_relaxed(value, aq->regs + reg);
>> +}
> 
> [...]
> 
>> +static int atmel_qspi_run_command(struct atmel_qspi *aq,
>> +				  const struct atmel_qspi_command *cmd)
>> +{
>> +	u32 iar, icr, ifr, sr;
>> +	int err = 0;
>> +
>> +	iar = 0;
>> +	icr = 0;
>> +	ifr = aq->ifr_width | cmd->ifr_tfrtyp;
>> +
>> +	/* Compute instruction parameters */
>> +	if (cmd->enable.bits.instruction) {
>> +		icr |= QSPI_ICR_INST(cmd->instruction);
>> +		ifr |= QSPI_IFR_INSTEN;
>> +	}
>> +
>> +	/* Compute address parameters */
>> +	switch (cmd->enable.bits.address) {
>> +	case 4:
>> +		ifr |= QSPI_IFR_ADDRL;
>> +		/*break;*/ /* fallback to the 24bit address case */
> 
> What's this commented out bit of code for ? :-)

I just wanted to stress out there was no missing "break;".
I've reworded the comment to:
/* No "break" on purpose: fallback to the 24bit address case. */

> 
>> +	case 3:
>> +		iar = (cmd->enable.bits.data) ? 0 : cmd->address;
>> +		ifr |= QSPI_IFR_ADDREN;
>> +		break;
>> +	case 0:
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
> 
> [...]
> 
>> +no_data:
>> +	/* Poll INSTRuction End status */
>> +	sr = qspi_readl(aq, QSPI_SR);
>> +	if (sr & QSPI_SR_INSTRE)
>> +		return err;
>> +
>> +	/* Wait for INSTRuction End interrupt */
>> +	init_completion(&aq->completion);
> 
> You should use reinit_completion() in the code. init_completion()
> should be used only in the probe() function and nowhere else.

Alright. In the next version I'll rename the "completion" member of
struct atmel_qspi into "cmd_completion". Also I'll add another dma_completion
member in this very same structure to replace the local
"struct completion completion" in atmel_qspi_run_dma_transfer().

Then I'll call init_completion() on both cmd_completion and dma_completion only
from atmel_qspi_probe() and reinit_completion() elsewhere.

> 
>> +	aq->pending = 0;
>> +	qspi_writel(aq, QSPI_IER, QSPI_SR_INSTRE);
>> +	if (!wait_for_completion_timeout(&aq->completion,
>> +					 msecs_to_jiffies(1000)))
>> +		err = -ETIMEDOUT;
>> +	qspi_writel(aq, QSPI_IDR, QSPI_SR_INSTRE);
>> +
>> +	return err;
>> +}
> 
> [...]
> 
> Hope this helps :)
> 

Indeed, it does! I still work on the next version of this series to take all your
comments into account.

Best regards,

Cyrille

Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Marek Vasut]

On Monday, August 24, 2015 at 07:04:38 PM, Cyrille Pitchen wrote:
> Hi Marek,

Hi!

> Le 24/08/2015 13:03, Marek Vasut a écrit :
> > On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
> >> This driver add support to the new Atmel QSPI controller embedded into
> >> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
> >> controller.

[...]

> >> +	/* Compute address parameters */
> >> +	switch (cmd->enable.bits.address) {
> >> +	case 4:
> >> +		ifr |= QSPI_IFR_ADDRL;
> >> +		/*break;*/ /* fallback to the 24bit address case */
> > 
> > What's this commented out bit of code for ? :-)
> 
> I just wanted to stress out there was no missing "break;".
> I've reworded the comment to:
> /* No "break" on purpose: fallback to the 24bit address case. */

Oh, the address is in bytes . I see, yes, it makes sense to be more
explicit here about the purpose of the fallback. I think this change
in the comment will make it easier for everyone who comes back in a
few years and reads this code.

> >> +	case 3:
> >> +		iar = (cmd->enable.bits.data) ? 0 : cmd->address;
> >> +		ifr |= QSPI_IFR_ADDREN;
> >> +		break;
> >> +	case 0:
> >> +		break;
> >> +	default:
> >> +		return -EINVAL;
> >> +	}
> > 
> > [...]
> > 
> >> +no_data:
> >> +	/* Poll INSTRuction End status */
> >> +	sr = qspi_readl(aq, QSPI_SR);
> >> +	if (sr & QSPI_SR_INSTRE)
> >> +		return err;
> >> +
> >> +	/* Wait for INSTRuction End interrupt */
> >> +	init_completion(&aq->completion);
> > 
> > You should use reinit_completion() in the code. init_completion()
> > should be used only in the probe() function and nowhere else.
> 
> Alright. In the next version I'll rename the "completion" member of
> struct atmel_qspi into "cmd_completion". Also I'll add another
> dma_completion member in this very same structure to replace the local
> "struct completion completion" in atmel_qspi_run_dma_transfer().
> 
> Then I'll call init_completion() on both cmd_completion and dma_completion
> only from atmel_qspi_probe() and reinit_completion() elsewhere.
> 
> >> +	aq->pending = 0;
> >> +	qspi_writel(aq, QSPI_IER, QSPI_SR_INSTRE);
> >> +	if (!wait_for_completion_timeout(&aq->completion,
> >> +					 msecs_to_jiffies(1000)))
> >> +		err = -ETIMEDOUT;
> >> +	qspi_writel(aq, QSPI_IDR, QSPI_SR_INSTRE);
> >> +
> >> +	return err;
> >> +}
> > 
> > [...]
> > 
> > Hope this helps :)
> 
> Indeed, it does! I still work on the next version of this series to take
> all your comments into account.

Thanks :)
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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Jonas Gorski]

On Mon, Aug 24, 2015 at 7:45 PM, Marek Vasut <marex-ynQEQJNshbs@public.gmane.org> wrote:
> On Monday, August 24, 2015 at 07:04:38 PM, Cyrille Pitchen wrote:
>> Hi Marek,
>
> Hi!
>
>> Le 24/08/2015 13:03, Marek Vasut a écrit :
>> > On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
>> >> This driver add support to the new Atmel QSPI controller embedded into
>> >> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
>> >> controller.
>
> [...]
>
>> >> +  /* Compute address parameters */
>> >> +  switch (cmd->enable.bits.address) {
>> >> +  case 4:
>> >> +          ifr |= QSPI_IFR_ADDRL;
>> >> +          /*break;*/ /* fallback to the 24bit address case */
>> >
>> > What's this commented out bit of code for ? :-)
>>
>> I just wanted to stress out there was no missing "break;".
>> I've reworded the comment to:
>> /* No "break" on purpose: fallback to the 24bit address case. */
>
> Oh, the address is in bytes . I see, yes, it makes sense to be more
> explicit here about the purpose of the fallback. I think this change
> in the comment will make it easier for everyone who comes back in a
> few years and reads this code.

I think you are looking for the term "(switch case) fallthrough", not
"fallback". "Fallback" makes it sound like there is something missing,
or an invalid state.


Jonas
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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Cyrille Pitchen]

Le 25/08/2015 11:46, Jonas Gorski a écrit :
> On Mon, Aug 24, 2015 at 7:45 PM, Marek Vasut <marex-ynQEQJNshbs@public.gmane.org> wrote:
>> On Monday, August 24, 2015 at 07:04:38 PM, Cyrille Pitchen wrote:
>>> Hi Marek,
>>
>> Hi!
>>
>>> Le 24/08/2015 13:03, Marek Vasut a écrit :
>>>> On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
>>>>> This driver add support to the new Atmel QSPI controller embedded into
>>>>> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
>>>>> controller.
>>
>> [...]
>>
>>>>> +  /* Compute address parameters */
>>>>> +  switch (cmd->enable.bits.address) {
>>>>> +  case 4:
>>>>> +          ifr |= QSPI_IFR_ADDRL;
>>>>> +          /*break;*/ /* fallback to the 24bit address case */
>>>>
>>>> What's this commented out bit of code for ? :-)
>>>
>>> I just wanted to stress out there was no missing "break;".
>>> I've reworded the comment to:
>>> /* No "break" on purpose: fallback to the 24bit address case. */
>>
>> Oh, the address is in bytes . I see, yes, it makes sense to be more
>> explicit here about the purpose of the fallback. I think this change
>> in the comment will make it easier for everyone who comes back in a
>> few years and reads this code.
> 
> I think you are looking for the term "(switch case) fallthrough", not
> "fallback". "Fallback" makes it sound like there is something missing,
> or an invalid state.
> 
> 
> Jonas
> 

will be modified in the next series, thanks for the review!
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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Cyrille Pitchen]

Hi Marek,

Le 24/08/2015 13:03, Marek Vasut a écrit :
> On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
>> This driver add support to the new Atmel QSPI controller embedded into
>> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
>> controller.
>>
>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> 
> Hi,
> 
> [...]
> 
>> +/* Register access macros */
> 
> These are functions, not macros :)
> 
> btw is there any reason for these ? I'd say, just put the read*() and
> write*() functions directly into the code and be done with it, it is
> much less confusing.

If you don't mind, I'd rather keep some of these inline functions. I have
no strong justification, it's more a personal taste: it makes lines
shorter as it avoids the need to add "->regs + ".
Also it makes the code consistent with other Atmel drivers which already
use such wrappers.

However I'll fix the comment and remove the byte and word versions, which
are not used. So only qspi_readl() and qspi_writel() are left.

Does it sound good to you?

> 
> Also, why do you use the _relaxed() versions of the functions ?
> 
>> +static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readl_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
>> +{
>> +	writel_relaxed(value, aq->regs + reg);
>> +}
>> +
>> +static inline u16 qspi_readw(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readw_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writew(struct atmel_qspi *aq, u32 reg, u16 value)
>> +{
>> +	writew_relaxed(value, aq->regs + reg);
>> +}
>> +
>> +static inline u8 qspi_readb(struct atmel_qspi *aq, u32 reg)
>> +{
>> +	return readb_relaxed(aq->regs + reg);
>> +}
>> +
>> +static inline void qspi_writeb(struct atmel_qspi *aq, u32 reg, u8 value)
>> +{
>> +	writeb_relaxed(value, aq->regs + reg);
>> +}
> 
> [...]
> 
> Hope this helps :)
> 

Best regards,

Cyrille

Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Marek Vasut]

On Tuesday, August 25, 2015 at 12:17:37 PM, Cyrille Pitchen wrote:
> Hi Marek,

Hi!

> Le 24/08/2015 13:03, Marek Vasut a écrit :
> > On Monday, August 24, 2015 at 12:14:00 PM, Cyrille Pitchen wrote:
> >> This driver add support to the new Atmel QSPI controller embedded into
> >> sama5d2x SoCs. It expects a NOR memory to be connected to the QSPI
> >> controller.
> >> 
> >> Signed-off-by: Cyrille Pitchen <cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> >> Acked-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> > 
> > Hi,
> > 
> > [...]
> > 
> >> +/* Register access macros */
> > 
> > These are functions, not macros :)
> > 
> > btw is there any reason for these ? I'd say, just put the read*() and
> > write*() functions directly into the code and be done with it, it is
> > much less confusing.
> 
> If you don't mind, I'd rather keep some of these inline functions. I have
> no strong justification, it's more a personal taste: it makes lines
> shorter as it avoids the need to add "->regs + ".
> Also it makes the code consistent with other Atmel drivers which already
> use such wrappers.
> 
> However I'll fix the comment and remove the byte and word versions, which
> are not used. So only qspi_readl() and qspi_writel() are left.
> 
> Does it sound good to you?

In my mind, seeing explicit readl_relaxed() somewhere is much easier to
digest than seeing some wrapper, which I have to look up. But please do
wait for others to voice their concern too, I might not be the best person
to tell you what to do when it comes to wrapping IO accessors ;-)

Best regards,
Marek Vasut
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Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Brian Norris]

On Tue, Aug 25, 2015 at 12:22:10PM +0200, Marek Vasut wrote:
> On Tuesday, August 25, 2015 at 12:17:37 PM, Cyrille Pitchen wrote:
> > If you don't mind, I'd rather keep some of these inline functions. I have
> > no strong justification, it's more a personal taste: it makes lines
> > shorter as it avoids the need to add "->regs + ".
> > Also it makes the code consistent with other Atmel drivers which already
> > use such wrappers.
> > 
> > However I'll fix the comment and remove the byte and word versions, which
> > are not used. So only qspi_readl() and qspi_writel() are left.
> > 
> > Does it sound good to you?
> 
> In my mind, seeing explicit readl_relaxed() somewhere is much easier to
> digest than seeing some wrapper, which I have to look up. But please do
> wait for others to voice their concern too, I might not be the best person
> to tell you what to do when it comes to wrapping IO accessors ;-)

I could go either way, but there are times where local wrapper I/O
accessors are useful. Case in point: it makes it really easy to make the
choice between readl() and readl_relaxed() in one place (i.e., the
discussion you had in another branch of this thread). That's been useful
for me on brcmnand, where certain platforms (big-endian MIPS) have
different assumptions about endianness than your average platform. Also,
it helps with things like what Robert Jarzmik is trying to do on
pxa3xx_nand -- add debug info to print every register read/write.

Also as Cyrille mentioned, personal taste is a factor.

Anyway, I'll go with whatever makes sense between y'all. I don't mind.

Brian
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RE: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Bean Huo 霍斌斌 (beanhuo)]

>+	nor->read_reg = atmel_qspi_read_reg;
>+	nor->write_reg = atmel_qspi_write_reg;
>+	nor->read = atmel_qspi_read;
>+	nor->write = atmel_qspi_write;
>+	nor->erase = atmel_qspi_erase;
>+	nor->set_protocol = atmel_qspi_set_protocol;

This is very good, the structure of spi_nor should add a hook function to notify spi controller 
That spi nor transfer protocol already changed.

>+
>+	if (of_modalias_node(child, modalias, sizeof(modalias)) < 0) {
>+		err = -ENODEV;
>+		goto release_channel;
>+	}
>+
>+	err = of_property_read_u32(child, "spi-max-frequency", &aq->clk_rate);
>+	if (err < 0)
>+		goto release_channel;
>+
>+	err = atmel_qspi_init(aq);
>+	if (err)
>+		goto release_channel;
>+
>+	nor->dev->of_node = child;
>+	err = spi_nor_scan(nor, modalias, SPI_NOR_QUAD);
>		goto release_channel;
>+


.......

>static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)  {
 	return mtd->priv;
>@@ -944,6 +960,11 @@ static int micron_quad_enable(struct spi_nor *nor)
>		return ret;
> 	}
> 
>+	/* switch protocol to Quad CMD 4-4-4 */
>+	ret = spi_nor_set_protocol(nor, SPI_PROTO_4_4_4);
>+	if (ret)
>+		return ret;
>+

This make sense,from spi nor side,once its protocol being changed,
Mtd layer must notify this status to spi nor controller immediately,
And spi nor controller also should re-adjust its protocol.
Otherwise, following reading SR operation will fail. 

>
> 	ret = spi_nor_wait_till_ready(nor);
> 	if (ret)
> 		return ret;

If my ack has any value in here, feel free to add it.

Acked-by: Bean Huo <beanhuo@micron.com>

Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

[Cyrille Pitchen]

Hi!

Le 25/08/2015 03:44, Bean Huo 霍斌斌 (beanhuo) a écrit :
> 
>> +	nor->read_reg = atmel_qspi_read_reg;
>> +	nor->write_reg = atmel_qspi_write_reg;
>> +	nor->read = atmel_qspi_read;
>> +	nor->write = atmel_qspi_write;
>> +	nor->erase = atmel_qspi_erase;
>> +	nor->set_protocol = atmel_qspi_set_protocol;
> 
> This is very good, the structure of spi_nor should add a hook function to notify spi controller 
> That spi nor transfer protocol already changed.
> 
>> +
>> +	if (of_modalias_node(child, modalias, sizeof(modalias)) < 0) {
>> +		err = -ENODEV;
>> +		goto release_channel;
>> +	}
>> +
>> +	err = of_property_read_u32(child, "spi-max-frequency", &aq->clk_rate);
>> +	if (err < 0)
>> +		goto release_channel;
>> +
>> +	err = atmel_qspi_init(aq);
>> +	if (err)
>> +		goto release_channel;
>> +
>> +	nor->dev->of_node = child;
>> +	err = spi_nor_scan(nor, modalias, SPI_NOR_QUAD);
>> 		goto release_channel;
>> +
> 
> 
> .......
> 
>> static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)  {
>  	return mtd->priv;
>> @@ -944,6 +960,11 @@ static int micron_quad_enable(struct spi_nor *nor)
>> 		return ret;
>> 	}
>>
>> +	/* switch protocol to Quad CMD 4-4-4 */
>> +	ret = spi_nor_set_protocol(nor, SPI_PROTO_4_4_4);
>> +	if (ret)
>> +		return ret;
>> +
> 
> This make sense,from spi nor side,once its protocol being changed,
> Mtd layer must notify this status to spi nor controller immediately,
> And spi nor controller also should re-adjust its protocol.
> Otherwise, following reading SR operation will fail. 
> 
>>
>> 	ret = spi_nor_wait_till_ready(nor);
>> 	if (ret)
>> 		return ret;
> 
> If my ack has any value in here, feel free to add it.
> 
> Acked-by: Bean Huo <beanhuo-AL4WhLSQfzjQT0dZR+AlfA@public.gmane.org>
> 

Since your comments deal with the protocol change, I'll add your ack to the
first patch of the series:
"mtd: spi-nor: notify (Q)SPI controller about protocol change"

Thanks for your review!

Best regards,

Cyrille

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