Re: [PATCH V3 6/6] bus: Add support for Tegra Generic Memory Interface

[Mirza Krak]

2016-11-03 11:51 GMT+01:00 Jon Hunter <jonathanh@xxxxxxxxxx>:
>
> On 27/10/16 15:01, Mirza Krak wrote:
>>
>> From: Mirza Krak <mirza.krak@xxxxxxxxx>
>>
>> The Generic Memory Interface bus can be used to connect high-speed
>> devices such as NOR flash, FPGAs, DSPs...
>>
>> Signed-off-by: Mirza Krak <mirza.krak@xxxxxxxxx>
>> Tested-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
>> Tested-on: Colibri T20/T30 on EvalBoard V3.x and GMI-Memory Board
>> ---
>>
>> Changes in v2:
>>  - Fixed some checkpatch errors
>>  - Re-ordered probe to get rid of local variables
>>  - Moved of_platform_default_populate call to the end of probe
>>  - Use the timing and configuration properties from the child device
>>  - Added warning if more then 1 child device exist
>>
>> Changes in v3:
>>  - added helper function to disable the controller which is used in remove
>> and
>>  on error.
>>  - Added logic to parse CS# from "ranges" property with fallback to "reg"
>>  property
>>
>>  drivers/bus/Kconfig     |   8 ++
>>  drivers/bus/Makefile    |   1 +
>>  drivers/bus/tegra-gmi.c | 267
>> ++++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 276 insertions(+)
>>  create mode 100644 drivers/bus/tegra-gmi.c
>>
>> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
>> index 4ed7d26..2e75a7f 100644
>> --- a/drivers/bus/Kconfig
>> +++ b/drivers/bus/Kconfig
>> @@ -141,6 +141,14 @@ config TEGRA_ACONNECT
>>           Driver for the Tegra ACONNECT bus which is used to interface
>> with
>>           the devices inside the Audio Processing Engine (APE) for
>> Tegra210.
>>
>> +config TEGRA_GMI
>> +       tristate "Tegra Generic Memory Interface bus driver"
>> +       depends on ARCH_TEGRA
>> +       help
>> +         Driver for the Tegra Generic Memory Interface bus which can be
>> used
>> +         to attach devices such as NOR, UART, FPGA and more.
>> +
>> +
>
>
> Nit-pick ... only one additional line above is needed to be consistent with
> the rest of the file.

Will fix that.

>
>
>>  config UNIPHIER_SYSTEM_BUS
>>         tristate "UniPhier System Bus driver"
>>         depends on ARCH_UNIPHIER && OF
>> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
>> index ac84cc4..34e2bab 100644
>> --- a/drivers/bus/Makefile
>> +++ b/drivers/bus/Makefile
>> @@ -18,5 +18,6 @@ obj-$(CONFIG_OMAP_OCP2SCP)    += omap-ocp2scp.o
>>  obj-$(CONFIG_SUNXI_RSB)                += sunxi-rsb.o
>>  obj-$(CONFIG_SIMPLE_PM_BUS)    += simple-pm-bus.o
>>  obj-$(CONFIG_TEGRA_ACONNECT)   += tegra-aconnect.o
>> +obj-$(CONFIG_TEGRA_GMI)                += tegra-gmi.o
>>  obj-$(CONFIG_UNIPHIER_SYSTEM_BUS)      += uniphier-system-bus.o
>>  obj-$(CONFIG_VEXPRESS_CONFIG)  += vexpress-config.o
>> diff --git a/drivers/bus/tegra-gmi.c b/drivers/bus/tegra-gmi.c
>> new file mode 100644
>> index 0000000..dd9623e
>> --- /dev/null
>> +++ b/drivers/bus/tegra-gmi.c
>> @@ -0,0 +1,267 @@
>> +/*
>> + * Driver for NVIDIA Generic Memory Interface
>> + *
>> + * Copyright (C) 2016 Host Mobility AB. All rights reserved.
>> + *
>> + * This file is licensed under the terms of the GNU General Public
>> + * License version 2. This program is licensed "as is" without any
>> + * warranty of any kind, whether express or implied.
>> + */
>> +#include <linux/clk.h>
>> +#include <linux/delay.h>
>> +#include <linux/io.h>
>> +#include <linux/module.h>
>> +#include <linux/of_device.h>
>> +#include <linux/reset.h>
>> +
>> +#define TEGRA_GMI_CONFIG               0x00
>> +#define TEGRA_GMI_CONFIG_GO            BIT(31)
>> +#define TEGRA_GMI_BUS_WIDTH_32BIT      BIT(30)
>> +#define TEGRA_GMI_MUX_MODE             BIT(28)
>> +#define TEGRA_GMI_RDY_BEFORE_DATA      BIT(24)
>> +#define TEGRA_GMI_RDY_ACTIVE_HIGH      BIT(23)
>> +#define TEGRA_GMI_ADV_ACTIVE_HIGH      BIT(22)
>> +#define TEGRA_GMI_OE_ACTIVE_HIGH       BIT(21)
>> +#define TEGRA_GMI_CS_ACTIVE_HIGH       BIT(20)
>> +#define TEGRA_GMI_CS_SELECT(x)         ((x & 0x7) << 4)
>> +
>> +#define TEGRA_GMI_TIMING0              0x10
>> +#define TEGRA_GMI_MUXED_WIDTH(x)       ((x & 0xf) << 12)
>> +#define TEGRA_GMI_HOLD_WIDTH(x)                ((x & 0xf) << 8)
>> +#define TEGRA_GMI_ADV_WIDTH(x)         ((x & 0xf) << 4)
>> +#define TEGRA_GMI_CE_WIDTH(x)          (x & 0xf)
>> +
>> +#define TEGRA_GMI_TIMING1              0x14
>> +#define TEGRA_GMI_WE_WIDTH(x)          ((x & 0xff) << 16)
>> +#define TEGRA_GMI_OE_WIDTH(x)          ((x & 0xff) << 8)
>> +#define TEGRA_GMI_WAIT_WIDTH(x)                (x & 0xff)
>> +
>> +struct tegra_gmi_priv {
>> +       void __iomem *base;
>> +       struct reset_control *rst;
>> +       struct clk *clk;
>> +
>> +       u32 snor_config;
>> +       u32 snor_timing0;
>> +       u32 snor_timing1;
>> +};
>> +
>> +static void tegra_gmi_disable(struct tegra_gmi_priv *priv)
>> +{
>> +       u32 config;
>> +
>> +       /* stop GMI operation */
>> +       config = readl(priv->base + TEGRA_GMI_CONFIG);
>> +       config &= ~TEGRA_GMI_CONFIG_GO;
>> +       writel(config, priv->base + TEGRA_GMI_CONFIG);
>> +
>> +       reset_control_assert(priv->rst);
>> +       clk_disable_unprepare(priv->clk);
>> +}
>> +
>> +static void tegra_gmi_init(struct device *dev, struct tegra_gmi_priv
>> *priv)
>> +{
>> +       writel(priv->snor_timing0, priv->base + TEGRA_GMI_TIMING0);
>> +       writel(priv->snor_timing1, priv->base + TEGRA_GMI_TIMING1);
>> +
>> +       priv->snor_config |= TEGRA_GMI_CONFIG_GO;
>> +       writel(priv->snor_config, priv->base + TEGRA_GMI_CONFIG);
>> +}
>> +
>> +static int tegra_gmi_parse_dt(struct device *dev, struct tegra_gmi_priv
>> *priv)
>> +{
>> +       struct device_node *child =
>> of_get_next_available_child(dev->of_node,
>> +               NULL);
>> +       u32 property, ranges[4];
>> +       int ret;
>> +
>> +       if (!child) {
>> +               dev_warn(dev, "no child nodes found\n");
>> +               return 0;
>
>
> Don't we want to return an error here? Otherwise, we will call
> tegra_gmi_init() with an invalid configuration.

True, we probably want that. My thought was that we might accept a
tegra-gmi node without any child nodes and just print a warning. But
since it is the child node that holds the bus configuration it makes
sense to fail probe due to no child nodes.

>
>
>> +       }
>> +
>> +       /*
>> +        * We currently only support one child device due to lack of
>> +        * chip-select address decoding. Which means that we only have one
>> +        * chip-select line from the GMI controller.
>> +        */
>> +       if (of_get_child_count(dev->of_node) > 1)
>> +               dev_warn(dev, "only one child device is supported.");
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-data-width-32bit"))
>> +               priv->snor_config |= TEGRA_GMI_BUS_WIDTH_32BIT;
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-mux-mode"))
>> +               priv->snor_config |= TEGRA_GMI_MUX_MODE;
>> +
>> +       if (of_property_read_bool(child,
>> "nvidia,snor-rdy-active-before-data"))
>> +               priv->snor_config |= TEGRA_GMI_RDY_BEFORE_DATA;
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-rdy-inv"))
>> +               priv->snor_config |= TEGRA_GMI_RDY_ACTIVE_HIGH;
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-adv-inv"))
>> +               priv->snor_config |= TEGRA_GMI_ADV_ACTIVE_HIGH;
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-oe-inv"))
>> +               priv->snor_config |= TEGRA_GMI_OE_ACTIVE_HIGH;
>> +
>> +       if (of_property_read_bool(child, "nvidia,snor-cs-inv"))
>> +               priv->snor_config |= TEGRA_GMI_CS_ACTIVE_HIGH;
>> +
>> +       /* Decode the CS# */
>> +       ret = of_property_read_u32_array(child, "ranges", ranges, 4);
>> +       if (ret < 0) {
>> +               /* Invalid binding */
>> +               if (ret == -EOVERFLOW) {
>> +                       dev_err(dev, "invalid ranges length\n");
>> +                       goto error_cs_decode;
>> +               }
>> +
>> +               /*
>> +                * If we reach here it means that the child node has an
>> empty
>> +                * ranges or it does not exist at all. Attempt to decode
>> the
>> +                * CS# from the reg property instead.
>> +                */
>> +               ret = of_property_read_u32(child, "reg", &property);
>> +               if (ret < 0) {
>> +                       dev_err(dev, "no reg property found\n");
>> +                       goto error_cs_decode;
>> +               }
>> +       } else {
>> +               property = ranges[1];
>> +       }
>> +
>> +       priv->snor_config |= TEGRA_GMI_CS_SELECT(property);
>
>
> Should we make sure the CS is a valid value before setting?

The TEGRA_GMI_CS_SELECT(x) macro will truncate any erroneous CS value.
But yeah we could do a sanity check instead and return an error if it
is invalid.

>
>
>> +
>> +       /* The default values that are provided below are reset values */
>> +       if (!of_property_read_u32(child, "nvidia,snor-muxed-width",
>> &property))
>> +               priv->snor_timing0 |= TEGRA_GMI_MUXED_WIDTH(property);
>> +       else
>> +               priv->snor_timing0 |= TEGRA_GMI_MUXED_WIDTH(1);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-hold-width",
>> &property))
>> +               priv->snor_timing0 |= TEGRA_GMI_HOLD_WIDTH(property);
>> +       else
>> +               priv->snor_timing0 |= TEGRA_GMI_HOLD_WIDTH(1);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-adv-width",
>> &property))
>> +               priv->snor_timing0 |= TEGRA_GMI_ADV_WIDTH(property);
>> +       else
>> +               priv->snor_timing0 |= TEGRA_GMI_ADV_WIDTH(1);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-ce-width",
>> &property))
>> +               priv->snor_timing0 |= TEGRA_GMI_CE_WIDTH(property);
>> +       else
>> +               priv->snor_timing0 |= TEGRA_GMI_CE_WIDTH(4);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-we-width",
>> &property))
>> +               priv->snor_timing1 |= TEGRA_GMI_WE_WIDTH(property);
>> +       else
>> +               priv->snor_timing1 |= TEGRA_GMI_WE_WIDTH(1);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-oe-width",
>> &property))
>> +               priv->snor_timing1 |= TEGRA_GMI_OE_WIDTH(property);
>> +       else
>> +               priv->snor_timing1 |= TEGRA_GMI_OE_WIDTH(1);
>> +
>> +       if (!of_property_read_u32(child, "nvidia,snor-wait-width",
>> &property))
>> +               priv->snor_timing1 |= TEGRA_GMI_WAIT_WIDTH(property);
>> +       else
>> +               priv->snor_timing1 |= TEGRA_GMI_WAIT_WIDTH(3);
>> +
>> +error_cs_decode:
>> +       if (ret < 0)
>> +               dev_err(dev, "failed to decode chip-select number\n");
>
>
> Nit do we need another error message here? Can we add the "failed to decode
> CS" part the earlier message?

Does it make sense to drop the two earlier messages instead and keep this one?

Best Regards
Mirza