Re: [PATCH] ipmi: bt-bmc: Use a regmap for register access

[Joel Stanley]

On Tue, Dec 6, 2016 at 1:27 PM, Andrew Jeffery <andrew@xxxxxxxx> wrote:
> The registers for the bt-bmc device live under the Aspeed LPC
> controller. Devicetree bindings have recently been introduced for the
> LPC controller where the "host" portion of the LPC register space is
> described as a syscon device. Future devicetrees describing the bt-bmc
> device should nest its node under the appropriate "simple-mfd", "syscon"
> compatible node.
>
> This change allows the bt-bmc driver to function with both syscon and
> non-syscon- based devicetree descriptions by always using a regmap for
> register access, either retrieved from the parent syscon device or
> instantiated if none exists.
>
> The patch has been tested on an OpenPOWER Palmetto machine, successfully
> booting, rebooting and powering down the host.
>
> Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> ---
>  drivers/char/ipmi/Kconfig  |  1 +
>  drivers/char/ipmi/bt-bmc.c | 82 ++++++++++++++++++++++++++++++++++------------
>  2 files changed, 62 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
> index 7f816655cbbf..b5d48d9af124 100644
> --- a/drivers/char/ipmi/Kconfig
> +++ b/drivers/char/ipmi/Kconfig
> @@ -79,6 +79,7 @@ endif # IPMI_HANDLER
>
>  config ASPEED_BT_IPMI_BMC
>         depends on ARCH_ASPEED

If you do a v2 of this series it would be great to add || COMPILE_TEST here.

> +        depends on REGMAP && REGMAP_MMIO && MFD_SYSCON
>         tristate "BT IPMI bmc driver"
>         help
>           Provides a driver for the BT (Block Transfer) IPMI interface
> diff --git a/drivers/char/ipmi/bt-bmc.c b/drivers/char/ipmi/bt-bmc.c
> index fc9e8891eae3..ca1e20f6c6c5 100644
> --- a/drivers/char/ipmi/bt-bmc.c
> +++ b/drivers/char/ipmi/bt-bmc.c
> @@ -12,10 +12,13 @@
>  #include <linux/errno.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
> +#include <linux/mfd/syscon.h>
>  #include <linux/miscdevice.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/poll.h>
> +#include <linux/regmap.h>
>  #include <linux/sched.h>
>  #include <linux/timer.h>
>
> @@ -60,7 +63,8 @@
>  struct bt_bmc {
>         struct device           dev;
>         struct miscdevice       miscdev;
> -       void __iomem            *base;
> +       struct regmap           *map;
> +       int                     offset;
>         int                     irq;
>         wait_queue_head_t       queue;
>         struct timer_list       poll_timer;
> @@ -69,14 +73,31 @@ struct bt_bmc {
>
>  static atomic_t open_count = ATOMIC_INIT(0);
>
> +static struct regmap_config bt_regmap_cfg = {

const?

> +       .reg_bits = 32,
> +       .val_bits = 32,
> +       .reg_stride = 4,
> +};
> +
>  static u8 bt_inb(struct bt_bmc *bt_bmc, int reg)
>  {
> -       return ioread8(bt_bmc->base + reg);
> +       uint32_t val = 0;
> +       int rc;
> +
> +       rc = regmap_read(bt_bmc->map, bt_bmc->offset + reg, &val);
> +       WARN(rc != 0, "%s:%d: regmap_read() failed: %d\n",
> +                       __FILE__, __LINE__, rc);

Under what circumstances do we expect the read to fail?

This isn't much cleaner, but I prefer it slightly:

rc = regmap_read(bt_bmc->map, bt_bmc->offset + reg, &val);
if (rc) {
   dev_warn(bt_bmc->dev, "read failed %d\n", rc);
   return rc;
}

return val;

> +
> +       return rc == 0 ? (u8) val : 0;
>  }
>
>  static void bt_outb(struct bt_bmc *bt_bmc, u8 data, int reg)
>  {
> -       iowrite8(data, bt_bmc->base + reg);
> +       int rc;
> +
> +       rc = regmap_write(bt_bmc->map, bt_bmc->offset + reg, data);
> +       WARN(rc != 0, "%s:%d: regmap_write() failed: %d\n",
> +                       __FILE__, __LINE__, rc);
>  }
>
>  static void clr_rd_ptr(struct bt_bmc *bt_bmc)
> @@ -367,14 +388,18 @@ static irqreturn_t bt_bmc_irq(int irq, void *arg)
>  {
>         struct bt_bmc *bt_bmc = arg;
>         u32 reg;
> +       int rc;
> +
> +       rc = regmap_read(bt_bmc->map, bt_bmc->offset + BT_CR2, &reg);
> +       if (rc)
> +               return IRQ_NONE;
>
> -       reg = ioread32(bt_bmc->base + BT_CR2);
>         reg &= BT_CR2_IRQ_H2B | BT_CR2_IRQ_HBUSY;
>         if (!reg)
>                 return IRQ_NONE;
>
>         /* ack pending IRQs */
> -       iowrite32(reg, bt_bmc->base + BT_CR2);
> +       regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR2, reg);
>
>         wake_up(&bt_bmc->queue);
>         return IRQ_HANDLED;
> @@ -384,7 +409,6 @@ static int bt_bmc_config_irq(struct bt_bmc *bt_bmc,
>                              struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
> -       u32 reg;
>         int rc;
>
>         bt_bmc->irq = platform_get_irq(pdev, 0);
> @@ -405,18 +429,17 @@ static int bt_bmc_config_irq(struct bt_bmc *bt_bmc,
>          * will be cleared (along with B2H) when we can write the next
>          * message to the BT buffer
>          */
> -       reg = ioread32(bt_bmc->base + BT_CR1);
> -       reg |= BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY;
> -       iowrite32(reg, bt_bmc->base + BT_CR1);
> +       rc = regmap_update_bits(bt_bmc->map, bt_bmc->offset + BT_CR1,
> +                               (BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY),
> +                               (BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY));

You could drop the ( ) around the flags if you want.

>
> -       return 0;
> +       return rc;
>  }
>
>  static int bt_bmc_probe(struct platform_device *pdev)
>  {
>         struct bt_bmc *bt_bmc;
>         struct device *dev;
> -       struct resource *res;
>         int rc;
>
>         if (!pdev || !pdev->dev.of_node)
> @@ -431,10 +454,27 @@ static int bt_bmc_probe(struct platform_device *pdev)
>
>         dev_set_drvdata(&pdev->dev, bt_bmc);
>
> -       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -       bt_bmc->base = devm_ioremap_resource(&pdev->dev, res);
> -       if (IS_ERR(bt_bmc->base))
> -               return PTR_ERR(bt_bmc->base);
> +       bt_bmc->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
> +       if (IS_ERR(bt_bmc->map)) {
> +               struct resource *res;
> +               void __iomem *base;
> +
> +               /*
> +                * Assume it's not the MFD-based devicetree description, in
> +                * which case generate a regmap ourselves
> +                */
> +               res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +               base = devm_ioremap_resource(&pdev->dev, res);
> +               if (IS_ERR(base))
> +                       return PTR_ERR(base);
> +
> +               bt_bmc->map = devm_regmap_init_mmio(dev, base, &bt_regmap_cfg);
> +               bt_bmc->offset = 0;
> +       } else {
> +               rc = of_property_read_u32(dev->of_node, "reg", &bt_bmc->offset);
> +               if (rc)
> +                       return rc;
> +       }
>
>         mutex_init(&bt_bmc->mutex);
>         init_waitqueue_head(&bt_bmc->queue);
> @@ -461,12 +501,12 @@ static int bt_bmc_probe(struct platform_device *pdev)
>                 add_timer(&bt_bmc->poll_timer);
>         }
>
> -       iowrite32((BT_IO_BASE << BT_CR0_IO_BASE) |
> -                 (BT_IRQ << BT_CR0_IRQ) |
> -                 BT_CR0_EN_CLR_SLV_RDP |
> -                 BT_CR0_EN_CLR_SLV_WRP |
> -                 BT_CR0_ENABLE_IBT,
> -                 bt_bmc->base + BT_CR0);
> +       regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR0,
> +                    (BT_IO_BASE << BT_CR0_IO_BASE) |
> +                    (BT_IRQ << BT_CR0_IRQ) |
> +                    BT_CR0_EN_CLR_SLV_RDP |
> +                    BT_CR0_EN_CLR_SLV_WRP |
> +                    BT_CR0_ENABLE_IBT);
>
>         clr_b_busy(bt_bmc);
>
> --
> 2.9.3
>