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SubjectRe: [PATCH v5 08/13] iommu/rockchip: Control clocks needed to access the IOMMU
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On 24/01/18 10:35, Jeffy Chen wrote:
> From: Tomasz Figa <tfiga@chromium.org>
>
> Current code relies on master driver enabling necessary clocks before
> IOMMU is accessed, however there are cases when the IOMMU should be
> accessed while the master is not running yet, for example allocating
> V4L2 videobuf2 buffers, which is done by the VB2 framework using DMA
> mapping API and doesn't engage the master driver at all.
>
> This patch fixes the problem by letting clocks needed for IOMMU
> operation to be listed in Device Tree and making the driver enable them
> for the time of accessing the hardware.
>
> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> Signed-off-by: Tomasz Figa <tfiga@chromium.org>
> ---
>
> Changes in v5:
> Use clk_bulk APIs.
>
> Changes in v4: None
> Changes in v3: None
> Changes in v2: None
>
> .../devicetree/bindings/iommu/rockchip,iommu.txt | 8 +++
> drivers/iommu/rockchip-iommu.c | 74 ++++++++++++++++++++--
> 2 files changed, 76 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> index 2098f7732264..33dd853359fa 100644
> --- a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> +++ b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> @@ -14,6 +14,13 @@ Required properties:
> "single-master" device, and needs no additional information
> to associate with its master device. See:
> Documentation/devicetree/bindings/iommu/iommu.txt
> +Optional properties:
> +- clocks : A list of master clocks requires for the IOMMU to be accessible

s/requires/required/

> + by the host CPU. The number of clocks depends on the master
> + block and might as well be zero. See [1] for generic clock

Oops, some subtleties of English here :)

To say "the number of clocks ... might as well be zero" effectively
implies "there's no point ever specifying any clocks". I guess what you
really mean here is "...might well be...", i.e. it is both valid and
reasonably likely to require zero clocks.

> + bindings description.
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
>
> Optional properties:
> - rockchip,disable-mmu-reset : Don't use the mmu reset operation.
> @@ -27,5 +34,6 @@ Example:
> reg = <0xff940300 0x100>;
> interrupts = <GIC_SPI 16 IRQ_TYPE_LEVEL_HIGH>;
> interrupt-names = "vopl_mmu";
> + clocks = <&cru ACLK_VOP1>, <&cru DCLK_VOP1>, <&cru HCLK_VOP1>;
> #iommu-cells = <0>;
> };
> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> index c4131ca792e0..8a5e2a659b67 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
> @@ -4,6 +4,7 @@
> * published by the Free Software Foundation.
> */
>
> +#include <linux/clk.h>
> #include <linux/compiler.h>
> #include <linux/delay.h>
> #include <linux/device.h>
> @@ -91,6 +92,8 @@ struct rk_iommu {
> struct device *dev;
> void __iomem **bases;
> int num_mmu;
> + struct clk_bulk_data *clocks;
> + int num_clocks;
> bool reset_disabled;
> struct iommu_device iommu;
> struct list_head node; /* entry in rk_iommu_domain.iommus */
> @@ -450,6 +453,38 @@ static int rk_iommu_force_reset(struct rk_iommu *iommu)
> return 0;
> }
>
> +static int rk_iommu_of_get_clocks(struct rk_iommu *iommu)
> +{
> + struct device_node *np = iommu->dev->of_node;
> + int ret;
> + int i;
> +
> + ret = of_count_phandle_with_args(np, "clocks", "#clock-cells");
> + if (ret == -ENOENT)
> + return 0;
> + else if (ret < 0)
> + return ret;
> +
> + iommu->num_clocks = ret;
> + iommu->clocks = devm_kcalloc(iommu->dev, iommu->num_clocks,
> + sizeof(*iommu->clocks), GFP_KERNEL);
> + if (!iommu->clocks)
> + return -ENOMEM;
> +
> + for (i = 0; i < iommu->num_clocks; ++i) {
> + iommu->clocks[i].clk = of_clk_get(np, i);
> + if (IS_ERR(iommu->clocks[i].clk)) {
> + ret = PTR_ERR(iommu->clocks[i].clk);
> + goto err_clk_put;
> + }
> + }

Just to confirm my understanding from a quick scan through the code, the
reason we can't use clk_bulk_get() here is that currently, clocks[i].id
being NULL means we'd end up just getting the first clock multiple
times, right?

I guess there could be other users who also want "just get whatever
clocks I have" functionality, so it might be worth proposing that for
the core API as a separate/follow-up patch, but it definitely doesn't
need to be part of this series.

I really don't know enough about correct clk API usage, but modulo the
binding comments it certainly looks nice and tidy now;

Acked-by: Robin Murphy <robin.murphy@arm.com>

Thanks,
Robin.

> +
> + return 0;
> +err_clk_put:
> + clk_bulk_put(i, iommu->clocks);
> + return ret;
> +}
> +
> static void log_iova(struct rk_iommu *iommu, int index, dma_addr_t iova)
> {
> void __iomem *base = iommu->bases[index];
> @@ -506,6 +541,8 @@ static irqreturn_t rk_iommu_irq(int irq, void *dev_id)
> irqreturn_t ret = IRQ_NONE;
> int i;
>
> + WARN_ON(clk_bulk_enable(iommu->num_clocks, iommu->clocks));
> +
> for (i = 0; i < iommu->num_mmu; i++) {
> int_status = rk_iommu_read(iommu->bases[i], RK_MMU_INT_STATUS);
> if (int_status == 0)
> @@ -552,6 +589,8 @@ static irqreturn_t rk_iommu_irq(int irq, void *dev_id)
> rk_iommu_write(iommu->bases[i], RK_MMU_INT_CLEAR, int_status);
> }
>
> + clk_bulk_disable(iommu->num_clocks, iommu->clocks);
> +
> return ret;
> }
>
> @@ -594,7 +633,9 @@ static void rk_iommu_zap_iova(struct rk_iommu_domain *rk_domain,
> list_for_each(pos, &rk_domain->iommus) {
> struct rk_iommu *iommu;
> iommu = list_entry(pos, struct rk_iommu, node);
> + WARN_ON(clk_bulk_enable(iommu->num_clocks, iommu->clocks));
> rk_iommu_zap_lines(iommu, iova, size);
> + clk_bulk_disable(iommu->num_clocks, iommu->clocks);
> }
> spin_unlock_irqrestore(&rk_domain->iommus_lock, flags);
> }
> @@ -823,10 +864,14 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
> if (!iommu)
> return 0;
>
> - ret = rk_iommu_enable_stall(iommu);
> + ret = clk_bulk_enable(iommu->num_clocks, iommu->clocks);
> if (ret)
> return ret;
>
> + ret = rk_iommu_enable_stall(iommu);
> + if (ret)
> + goto out_disable_clocks;
> +
> ret = rk_iommu_force_reset(iommu);
> if (ret)
> goto out_disable_stall;
> @@ -852,6 +897,8 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
>
> out_disable_stall:
> rk_iommu_disable_stall(iommu);
> +out_disable_clocks:
> + clk_bulk_disable(iommu->num_clocks, iommu->clocks);
> return ret;
> }
>
> @@ -873,6 +920,7 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
> spin_unlock_irqrestore(&rk_domain->iommus_lock, flags);
>
> /* Ignore error while disabling, just keep going */
> + WARN_ON(clk_bulk_enable(iommu->num_clocks, iommu->clocks));
> rk_iommu_enable_stall(iommu);
> rk_iommu_disable_paging(iommu);
> for (i = 0; i < iommu->num_mmu; i++) {
> @@ -880,6 +928,7 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
> rk_iommu_write(iommu->bases[i], RK_MMU_DTE_ADDR, 0);
> }
> rk_iommu_disable_stall(iommu);
> + clk_bulk_disable(iommu->num_clocks, iommu->clocks);
>
> iommu->domain = NULL;
>
> @@ -1172,18 +1221,31 @@ static int rk_iommu_probe(struct platform_device *pdev)
> iommu->reset_disabled = device_property_read_bool(dev,
> "rockchip,disable-mmu-reset");
>
> - err = iommu_device_sysfs_add(&iommu->iommu, dev, NULL, dev_name(dev));
> + err = rk_iommu_of_get_clocks(iommu);
> if (err)
> return err;
>
> + err = clk_bulk_prepare(iommu->num_clocks, iommu->clocks);
> + if (err)
> + goto err_put_clocks;
> +
> + err = iommu_device_sysfs_add(&iommu->iommu, dev, NULL, dev_name(dev));
> + if (err)
> + goto err_unprepare_clocks;
> +
> iommu_device_set_ops(&iommu->iommu, &rk_iommu_ops);
> err = iommu_device_register(&iommu->iommu);
> - if (err) {
> - iommu_device_sysfs_remove(&iommu->iommu);
> - return err;
> - }
> + if (err)
> + goto err_remove_sysfs;
>
> return 0;
> +err_remove_sysfs:
> + iommu_device_sysfs_remove(&iommu->iommu);
> +err_unprepare_clocks:
> + clk_bulk_unprepare(iommu->num_clocks, iommu->clocks);
> +err_put_clocks:
> + clk_bulk_put(iommu->num_clocks, iommu->clocks);
> + return err;
> }
>
> static const struct of_device_id rk_iommu_dt_ids[] = {
>

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