[PATCH] ipmi: bt-bmc: Use registers directly

[Joel Stanley]

Hi Corey,

On Fri, 3 Sept 2021 at 05:10, Joel Stanley <joel at jms.id.au> wrote:
>
> This driver was originally written to use the regmap abstraction with no
> clear benefit. As the registers are always mmio and there is no sharing
> of the region with other devices, we can safely read and write without
> the locking that regmap provides.
>
> This reduces the code size of the driver by about 25%.

Do you have any feedback on this one?

Cheers,

Joel


>
> Signed-off-by: Joel Stanley <joel at jms.id.au>
> ---
>  drivers/char/ipmi/bt-bmc.c | 68 +++++++++-----------------------------
>  1 file changed, 16 insertions(+), 52 deletions(-)
>
> diff --git a/drivers/char/ipmi/bt-bmc.c b/drivers/char/ipmi/bt-bmc.c
> index 6e3d247b55d1..fb771ce6f7bf 100644
> --- a/drivers/char/ipmi/bt-bmc.c
> +++ b/drivers/char/ipmi/bt-bmc.c
> @@ -8,13 +8,11 @@
>  #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>
>
> @@ -59,8 +57,7 @@
>  struct bt_bmc {
>         struct device           dev;
>         struct miscdevice       miscdev;
> -       struct regmap           *map;
> -       int                     offset;
> +       void __iomem            *base;
>         int                     irq;
>         wait_queue_head_t       queue;
>         struct timer_list       poll_timer;
> @@ -69,29 +66,14 @@ struct bt_bmc {
>
>  static atomic_t open_count = ATOMIC_INIT(0);
>
> -static const struct regmap_config bt_regmap_cfg = {
> -       .reg_bits = 32,
> -       .val_bits = 32,
> -       .reg_stride = 4,
> -};
> -
>  static u8 bt_inb(struct bt_bmc *bt_bmc, int reg)
>  {
> -       uint32_t val = 0;
> -       int rc;
> -
> -       rc = regmap_read(bt_bmc->map, bt_bmc->offset + reg, &val);
> -       WARN(rc != 0, "regmap_read() failed: %d\n", rc);
> -
> -       return rc == 0 ? (u8) val : 0;
> +       return readb(bt_bmc->base + reg);
>  }
>
>  static void bt_outb(struct bt_bmc *bt_bmc, u8 data, int reg)
>  {
> -       int rc;
> -
> -       rc = regmap_write(bt_bmc->map, bt_bmc->offset + reg, data);
> -       WARN(rc != 0, "regmap_write() failed: %d\n", rc);
> +       writeb(data, bt_bmc->base + reg);
>  }
>
>  static void clr_rd_ptr(struct bt_bmc *bt_bmc)
> @@ -376,18 +358,15 @@ 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 = readl(bt_bmc->base + BT_CR2);
>
>         reg &= BT_CR2_IRQ_H2B | BT_CR2_IRQ_HBUSY;
>         if (!reg)
>                 return IRQ_NONE;
>
>         /* ack pending IRQs */
> -       regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR2, reg);
> +       writel(reg, bt_bmc->base + BT_CR2);
>
>         wake_up(&bt_bmc->queue);
>         return IRQ_HANDLED;
> @@ -398,6 +377,7 @@ static int bt_bmc_config_irq(struct bt_bmc *bt_bmc,
>  {
>         struct device *dev = &pdev->dev;
>         int rc;
> +       u32 reg;
>
>         bt_bmc->irq = platform_get_irq_optional(pdev, 0);
>         if (bt_bmc->irq < 0)
> @@ -417,11 +397,11 @@ 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
>          */
> -       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));
> +       reg = readl(bt_bmc->base + BT_CR1);
> +       reg |= BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY;
> +       writel(reg, bt_bmc->base + BT_CR1);
>
> -       return rc;
> +       return 0;
>  }
>
>  static int bt_bmc_probe(struct platform_device *pdev)
> @@ -439,25 +419,9 @@ static int bt_bmc_probe(struct platform_device *pdev)
>
>         dev_set_drvdata(&pdev->dev, bt_bmc);
>
> -       bt_bmc->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
> -       if (IS_ERR(bt_bmc->map)) {
> -               void __iomem *base;
> -
> -               /*
> -                * Assume it's not the MFD-based devicetree description, in
> -                * which case generate a regmap ourselves
> -                */
> -               base = devm_platform_ioremap_resource(pdev, 0);
> -               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;
> -       }
> +       bt_bmc->base = devm_platform_ioremap_resource(pdev, 0);
> +       if (IS_ERR(bt_bmc->base))
> +               return PTR_ERR(bt_bmc->base);
>
>         mutex_init(&bt_bmc->mutex);
>         init_waitqueue_head(&bt_bmc->queue);
> @@ -483,12 +447,12 @@ static int bt_bmc_probe(struct platform_device *pdev)
>                 add_timer(&bt_bmc->poll_timer);
>         }
>
> -       regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR0,
> -                    (BT_IO_BASE << BT_CR0_IO_BASE) |
> +       writel((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_CR0_ENABLE_IBT,
> +               bt_bmc->base + BT_CR0);
>
>         clr_b_busy(bt_bmc);
>
> --
> 2.33.0
>