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Subject: Re: [PATCH v4 05/13] iommu/rockchip: Use iopoll helpers to wait for
 hardware
To:     Jeffy Chen <jeffy.chen@rock-chips.com>,
        linux-kernel@vger.kernel.org, tfiga@chromium.org
Cc:     jcliang@chromium.org, xxm@rock-chips.com,
        Heiko Stuebner <heiko@sntech.de>,
        linux-rockchip@lists.infradead.org,
        iommu@lists.linux-foundation.org, Joerg Roedel <joro@8bytes.org>,
        linux-arm-kernel@lists.infradead.org
References: <20180118115251.5542-1-jeffy.chen@rock-chips.com>
 <20180118115251.5542-6-jeffy.chen@rock-chips.com>
From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <064794b9-98ae-221e-76bd-e11130514826@arm.com>
Date:   Thu, 18 Jan 2018 13:09:27 +0000
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On 18/01/18 11:52, Jeffy Chen wrote:
> From: Tomasz Figa <tfiga@chromium.org>
> 
> This patch converts the rockchip-iommu driver to use the in-kernel
> iopoll helpers to wait for certain status bits to change in registers
> instead of an open-coded custom macro.
> 
> Signed-off-by: Tomasz Figa <tfiga@chromium.org>
> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> ---
> 
> Changes in v4: None
> Changes in v3: None
> Changes in v2: None
> 
>   drivers/iommu/rockchip-iommu.c | 68 ++++++++++++++++++++----------------------
>   1 file changed, 32 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> index 37065a7127c9..4a1c710408af 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
> @@ -13,7 +13,7 @@
>   #include <linux/interrupt.h>
>   #include <linux/io.h>
>   #include <linux/iommu.h>
> -#include <linux/jiffies.h>
> +#include <linux/iopoll.h>
>   #include <linux/list.h>
>   #include <linux/mm.h>
>   #include <linux/module.h>
> @@ -36,7 +36,8 @@
>   #define RK_MMU_AUTO_GATING	0x24
>   
>   #define DTE_ADDR_DUMMY		0xCAFEBABE
> -#define FORCE_RESET_TIMEOUT	100	/* ms */
> +#define FORCE_RESET_TIMEOUT	100000	/* us */
> +#define POLL_TIMEOUT		1000	/* us */

Nit: the callsites look a bit odd with the combination of POLL_TIMEOUT 
and the magic number 100 - should we not also define something like 
POLL_PERIOD for that? Also POLL_TIMEOUT is a rather generic name and 
overlaps with several other drivers, so a namespace prefix would be 
helpful (i.e. RK_IOMMU_POLL*, or at least RK_POLL*).

FWIW, my personal preference would be to also suffix these with _US for 
absolute clarity, but it's not essential (especially if longer names 
lead to more linebreaks at the callsites).

With those undocumented "100"s fixed up,

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

>   /* RK_MMU_STATUS fields */
>   #define RK_MMU_STATUS_PAGING_ENABLED       BIT(0)
> @@ -73,8 +74,6 @@
>     */
>   #define RK_IOMMU_PGSIZE_BITMAP 0x007ff000
>   
> -#define IOMMU_REG_POLL_COUNT_FAST 1000
> -
>   struct rk_iommu_domain {
>   	struct list_head iommus;
>   	struct platform_device *pdev;
> @@ -109,27 +108,6 @@ static struct rk_iommu_domain *to_rk_domain(struct iommu_domain *dom)
>   	return container_of(dom, struct rk_iommu_domain, domain);
>   }
>   
> -/**
> - * Inspired by _wait_for in intel_drv.h
> - * This is NOT safe for use in interrupt context.
> - *
> - * Note that it's important that we check the condition again after having
> - * timed out, since the timeout could be due to preemption or similar and
> - * we've never had a chance to check the condition before the timeout.
> - */
> -#define rk_wait_for(COND, MS) ({ \
> -	unsigned long timeout__ = jiffies + msecs_to_jiffies(MS) + 1;	\
> -	int ret__ = 0;							\
> -	while (!(COND)) {						\
> -		if (time_after(jiffies, timeout__)) {			\
> -			ret__ = (COND) ? 0 : -ETIMEDOUT;		\
> -			break;						\
> -		}							\
> -		usleep_range(50, 100);					\
> -	}								\
> -	ret__;								\
> -})
> -
>   /*
>    * The Rockchip rk3288 iommu uses a 2-level page table.
>    * The first level is the "Directory Table" (DT).
> @@ -333,9 +311,21 @@ static bool rk_iommu_is_paging_enabled(struct rk_iommu *iommu)
>   	return enable;
>   }
>   
> +static bool rk_iommu_is_reset_done(struct rk_iommu *iommu)
> +{
> +	bool done = true;
> +	int i;
> +
> +	for (i = 0; i < iommu->num_mmu; i++)
> +		done &= rk_iommu_read(iommu->bases[i], RK_MMU_DTE_ADDR) == 0;
> +
> +	return done;
> +}
> +
>   static int rk_iommu_enable_stall(struct rk_iommu *iommu)
>   {
>   	int ret, i;
> +	bool val;
>   
>   	if (rk_iommu_is_stall_active(iommu))
>   		return 0;
> @@ -346,7 +336,8 @@ static int rk_iommu_enable_stall(struct rk_iommu *iommu)
>   
>   	rk_iommu_command(iommu, RK_MMU_CMD_ENABLE_STALL);
>   
> -	ret = rk_wait_for(rk_iommu_is_stall_active(iommu), 1);
> +	ret = readx_poll_timeout(rk_iommu_is_stall_active, iommu, val,
> +				 val, 100, POLL_TIMEOUT);
>   	if (ret)
>   		for (i = 0; i < iommu->num_mmu; i++)
>   			dev_err(iommu->dev, "Enable stall request timed out, status: %#08x\n",
> @@ -358,13 +349,15 @@ static int rk_iommu_enable_stall(struct rk_iommu *iommu)
>   static int rk_iommu_disable_stall(struct rk_iommu *iommu)
>   {
>   	int ret, i;
> +	bool val;
>   
>   	if (!rk_iommu_is_stall_active(iommu))
>   		return 0;
>   
>   	rk_iommu_command(iommu, RK_MMU_CMD_DISABLE_STALL);
>   
> -	ret = rk_wait_for(!rk_iommu_is_stall_active(iommu), 1);
> +	ret = readx_poll_timeout(rk_iommu_is_stall_active, iommu, val,
> +				 !val, 100, POLL_TIMEOUT);
>   	if (ret)
>   		for (i = 0; i < iommu->num_mmu; i++)
>   			dev_err(iommu->dev, "Disable stall request timed out, status: %#08x\n",
> @@ -376,13 +369,15 @@ static int rk_iommu_disable_stall(struct rk_iommu *iommu)
>   static int rk_iommu_enable_paging(struct rk_iommu *iommu)
>   {
>   	int ret, i;
> +	bool val;
>   
>   	if (rk_iommu_is_paging_enabled(iommu))
>   		return 0;
>   
>   	rk_iommu_command(iommu, RK_MMU_CMD_ENABLE_PAGING);
>   
> -	ret = rk_wait_for(rk_iommu_is_paging_enabled(iommu), 1);
> +	ret = readx_poll_timeout(rk_iommu_is_paging_enabled, iommu, val,
> +				 val, 100, POLL_TIMEOUT);
>   	if (ret)
>   		for (i = 0; i < iommu->num_mmu; i++)
>   			dev_err(iommu->dev, "Enable paging request timed out, status: %#08x\n",
> @@ -394,13 +389,15 @@ static int rk_iommu_enable_paging(struct rk_iommu *iommu)
>   static int rk_iommu_disable_paging(struct rk_iommu *iommu)
>   {
>   	int ret, i;
> +	bool val;
>   
>   	if (!rk_iommu_is_paging_enabled(iommu))
>   		return 0;
>   
>   	rk_iommu_command(iommu, RK_MMU_CMD_DISABLE_PAGING);
>   
> -	ret = rk_wait_for(!rk_iommu_is_paging_enabled(iommu), 1);
> +	ret = readx_poll_timeout(rk_iommu_is_paging_enabled, iommu, val,
> +				 !val, 100, POLL_TIMEOUT);
>   	if (ret)
>   		for (i = 0; i < iommu->num_mmu; i++)
>   			dev_err(iommu->dev, "Disable paging request timed out, status: %#08x\n",
> @@ -413,6 +410,7 @@ static int rk_iommu_force_reset(struct rk_iommu *iommu)
>   {
>   	int ret, i;
>   	u32 dte_addr;
> +	bool val;
>   
>   	if (iommu->reset_disabled)
>   		return 0;
> @@ -433,13 +431,11 @@ static int rk_iommu_force_reset(struct rk_iommu *iommu)
>   
>   	rk_iommu_command(iommu, RK_MMU_CMD_FORCE_RESET);
>   
> -	for (i = 0; i < iommu->num_mmu; i++) {
> -		ret = rk_wait_for(rk_iommu_read(iommu->bases[i], RK_MMU_DTE_ADDR) == 0x00000000,
> -				  FORCE_RESET_TIMEOUT);
> -		if (ret) {
> -			dev_err(iommu->dev, "FORCE_RESET command timed out\n");
> -			return ret;
> -		}
> +	ret = readx_poll_timeout(rk_iommu_is_reset_done, iommu, val,
> +				 val, 100, FORCE_RESET_TIMEOUT);
> +	if (ret) {
> +		dev_err(iommu->dev, "FORCE_RESET command timed out\n");
> +		return ret;
>   	}
>   
>   	return 0;
>