[U-Boot] [PATCH 1/6] dm: implement a DMA uclass

[Mugunthan V N <mugunthanvnm@ti.com>]

On Wednesday 02 December 2015 03:24 AM, Simon Glass wrote:
> Hi Mugunthan,
> 
> On 1 December 2015 at 04:13, Mugunthan V N <mugunthanvnm@ti.com> wrote:
>> Implement a DMA uclass so that the devices like ethernet, spi,
>> mmc etc can offload the data transfers from/to the device and
>> memory.
>>
>> Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
>> ---
>>  drivers/dma/Kconfig      | 15 ++++++++++++
>>  drivers/dma/Makefile     |  2 ++
>>  drivers/dma/dma-uclass.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++
>>  include/dm/uclass-id.h   |  1 +
>>  include/dma.h            | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 145 insertions(+)
>>  create mode 100644 drivers/dma/dma-uclass.c
>>  create mode 100644 include/dma.h
>>
>> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
>> index e69de29..af15199 100644
>> --- a/drivers/dma/Kconfig
>> +++ b/drivers/dma/Kconfig
>> @@ -0,0 +1,15 @@
>> +menu "DMA Support"
>> +
>> +config DM_DMA
>> +       bool "Enable Driver Model for DMA drivers"
>> +       depends on DM
>> +       help
>> +         Enable driver model for DMA. DMA engines can do
>> +         asynchronous data transfers without involving the host
>> +         CPU. Currently, this framework can be used to offload
>> +         memory copies to and from devices like qspi, ethernet
>> +         etc Drivers provide methods to access the DMA devices
>> +         buses that is used to transfer data to and from memory.
>> +         The uclass interface is defined in include/dma.h.
>> +
>> +endmenu # menu "DMA Support"
>> diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
>> index f95fe70..4ff22aa 100644
>> --- a/drivers/dma/Makefile
>> +++ b/drivers/dma/Makefile
>> @@ -5,6 +5,8 @@
>>  # SPDX-License-Identifier:     GPL-2.0+
>>  #
>>
>> +obj-$(CONFIG_DM_DMA) += dma-uclass.o
> 
> You can just use CONFIG_DMA. The DM_ prefix is for when we have an
> existing pre-DM interface. Eventually all the CONFIG_DM_... options
> will be removed. Unless you have a special reason?

For consistency I used CONFIG_DM_DMA, will rename it to CONFIG_DMA.

> 
>> +
>>  obj-$(CONFIG_FSLDMAFEC) += MCD_tasksInit.o MCD_dmaApi.o MCD_tasks.o
>>  obj-$(CONFIG_APBH_DMA) += apbh_dma.o
>>  obj-$(CONFIG_FSL_DMA) += fsl_dma.o
>> diff --git a/drivers/dma/dma-uclass.c b/drivers/dma/dma-uclass.c
>> new file mode 100644
>> index 0000000..1afcbaa4
>> --- /dev/null
>> +++ b/drivers/dma/dma-uclass.c
>> @@ -0,0 +1,63 @@
>> +/*
>> + * Direct Memory Access U-Class driver
>> + *
>> + * (C) Copyright 2015
>> + *     Texas Instruments Incorporated, <www.ti.com>
>> + *
>> + * Author: Mugunthan V N <mugunthanvnm@ti.com>
>> + *
>> + * SPDX-License-Identifier:     GPL-2.0+
>> + */
>> +
>> +#include <common.h>
>> +#include <dma.h>
>> +#include <dm.h>
>> +#include <dm/uclass-internal.h>
>> +#include <errno.h>
>> +
>> +DECLARE_GLOBAL_DATA_PTR;
>> +
>> +int dma_memcpy(void *dst, void *src, size_t len)
>> +{
>> +       struct udevice *dev;
>> +       const struct dma_ops *ops;
>> +       int ret;
>> +
>> +       for (ret = uclass_find_first_device(UCLASS_DMA, &dev); dev && !ret;
>> +            ret = uclass_find_next_device(&dev)) {
>> +               struct dma_dev_priv *uc_priv = dev_get_uclass_priv(dev);
>> +
>> +               if (uc_priv->supported & SUPPORTS_MEM_TO_MEM)
>> +                       break;
>> +       }
>> +
>> +       if (!dev) {
>> +               printf("No DMA device found that supports mem to mem transfers\n");
>> +               return -ENODEV;
>> +       }
> 
> Can you put the above code in a separate function like:
> 
> static int get_dma_device(struct udevice **devp)
> 
> also also please call device_probe() on it before returning it.

Okay, will do it in next version.

> 
>> +
>> +       ops = device_get_ops(dev);
>> +       if (!ops->transfer)
>> +               return -ENOSYS;
>> +
>> +       /* Invalidate the area, so no writeback into the RAM races with DMA */
>> +       invalidate_dcache_range((unsigned long)dst, (unsigned long)dst +
>> +                               roundup(len, ARCH_DMA_MINALIGN));
>> +
>> +       return ops->transfer(dev, DMA_MEM_TO_MEM, dst, src, len);
>> +}
>> +
>> +int dma_post_bind(struct udevice *dev)
>> +{
>> +       struct udevice *devp;
>> +       uclass_get_device_by_of_offset(UCLASS_DMA, dev->of_offset, &devp);
> 
> You are not allowed to do this in the post_bind() method. See above
> for how it should get probed.
> 

Okay, agreed.

>> +       return 0;
>> +}
>> +
>> +UCLASS_DRIVER(dma) = {
>> +       .id             = UCLASS_DMA,
>> +       .name           = "dma",
>> +       .flags          = DM_UC_FLAG_SEQ_ALIAS,
>> +       .per_device_auto_alloc_size = sizeof(struct dma_dev_priv),
>> +       .post_bind      = dma_post_bind,
>> +};
>> diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
>> index 27fa0b6..9f5fcae 100644
>> --- a/include/dm/uclass-id.h
>> +++ b/include/dm/uclass-id.h
>> @@ -30,6 +30,7 @@ enum uclass_id {
>>         UCLASS_CPU,             /* CPU, typically part of an SoC */
>>         UCLASS_CROS_EC,         /* Chrome OS EC */
>>         UCLASS_DISPLAY_PORT,    /* Display port video */
>> +       UCLASS_DMA,             /* Direct Memory Access */
>>         UCLASS_RAM,             /* RAM controller */
>>         UCLASS_ETH,             /* Ethernet device */
>>         UCLASS_GPIO,            /* Bank of general-purpose I/O pins */
>> diff --git a/include/dma.h b/include/dma.h
>> new file mode 100644
>> index 0000000..d53e435
>> --- /dev/null
>> +++ b/include/dma.h
>> @@ -0,0 +1,64 @@
>> +/*
>> + * (C) Copyright 2015
>> + *     Texas Instruments Incorporated, <www.ti.com>
>> + *
>> + * SPDX-License-Identifier:     GPL-2.0+
>> + */
>> +
>> +#ifndef _DMA_H_
>> +#define _DMA_H_
>> +
>> +/*
>> + * enum dma_direction - dma transfer direction indicator
>> + * @DMA_MEM_TO_MEM: Memcpy mode
>> + * @DMA_MEM_TO_DEV: From Memory to Device
>> + * @DMA_DEV_TO_MEM: From Device to Memory
>> + * @DMA_DEV_TO_DEV: From Device to Device
>> + */
>> +enum dma_direction {
>> +       DMA_MEM_TO_MEM,
>> +       DMA_MEM_TO_DEV,
>> +       DMA_DEV_TO_MEM,
>> +       DMA_DEV_TO_DEV,
>> +       DMA_TRANS_NONE,
> 
> What does that mean?

DMA driver will be having only one transfer api and to identify what
kind of transfer that the user driver is expecting, these enums are used.

> 
>> +};
>> +
>> +#define SUPPORTS_MEM_TO_MEM    BIT(0)
>> +#define SUPPORTS_MEM_TO_DEV    BIT(1)
>> +#define SUPPORTS_DEV_TO_MEM    BIT(2)
>> +#define SUPPORTS_DEV_TO_DEV    BIT(3)
> 
> DMA_ prefix on these. Also you could put them in an enum so they are grouped.

Will add DMA prefix to these defines.

Since a dma driver can support multiple transfer types I kept this as
bit level definitions, so that driver can intimate DMA framework like
uc_priv->supported = SUPPORTS_MEM_TO_MEM | SUPPORTS_MEM_TO_DEV;

> 
>> +
>> +/*
>> + * struct dma_ops - Driver model DMA operations
>> + *
>> + * The uclass interface is implemented by all DMA devices which use
>> + * driver model.
>> + */
>> +struct dma_ops {
>> +       /*
>> +        * Get the current timer count
> 
> Incorrect comment.
> 
>> +        *
>> +        * @dev: The DMA device
>> +        * @direction: direction of data transfer should be one from
>> +                      enum dma_direction
>> +        * @dst: Destination pointer
>> +        * @src: Source pointer
> 
> Any alignment restructions?

I should be aligned to DMA device alignment restrictions.

> 
>> +        * @len: Length of the data to be copied.
> 
> In bytes?

Okay

> 
>> +        * @return: 0 if OK, -ve on error
>> +        */
>> +       int (*transfer)(struct udevice *dev, int direction, void *dst,
> 
> s/int direction/enum dma_direction direction/

Okay

> 
>> +                       void *src, size_t len);
>> +};
>> +
>> +/*
>> + * struct dma_dev_priv - information about a device used by the uclass
>> + *
>> + * @supported: mode of transfers that DMA can support
> 
> Please reference where these flags come from.

Okay

> 
>> + */
>> +struct dma_dev_priv {
>> +       unsigned long supported;
> 
> int or uint should be enough.

Will used uint.

> 
>> +};
>> +
>> +int dma_memcpy(void *dst, void *src, size_t len);
>> +
>> +#endif /* _DMA_H_ */
>> --
>> 2.6.3.368.gf34be46
>>
> 
> Regards,
> Simon
> 

Regards
Mugunthan V N