[PATCH] clk: tegra: bpmp: Clamp clock rates on requests

[PATCH] clk: tegra: bpmp: Clamp clock rates on requests

[Mikko Perttunen]

From: Sivaram Nair <sivaramn@nvidia.com>

BPMP firmware ABI expects the rate inputs in int64_t. However,
tegra_bpmp_clk_round_rate() and tegra_bpmp_clk_set_rate() functions
directly assign 'unsigned long' inputs to a int64_t value causing
unexpected rounding errors.

Fix this by clipping the input rate to S64_MAX.

Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
[mperttunen: slight cleanup]
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
---
 drivers/clk/tegra/clk-bpmp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/tegra/clk-bpmp.c b/drivers/clk/tegra/clk-bpmp.c
index a66263b6490d..6ecf18f71c32 100644
--- a/drivers/clk/tegra/clk-bpmp.c
+++ b/drivers/clk/tegra/clk-bpmp.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (C) 2016 NVIDIA Corporation
+ * Copyright (C) 2016-2020 NVIDIA Corporation
  */
 
 #include <linux/clk-provider.h>
@@ -174,7 +174,7 @@ static long tegra_bpmp_clk_round_rate(struct clk_hw *hw, unsigned long rate,
 	int err;
 
 	memset(&request, 0, sizeof(request));
-	request.rate = rate;
+	request.rate = min_t(u64, rate, S64_MAX);
 
 	memset(&msg, 0, sizeof(msg));
 	msg.cmd = CMD_CLK_ROUND_RATE;
@@ -256,7 +256,7 @@ static int tegra_bpmp_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 	struct tegra_bpmp_clk_message msg;
 
 	memset(&request, 0, sizeof(request));
-	request.rate = rate;
+	request.rate = min_t(u64, rate, S64_MAX);
 
 	memset(&msg, 0, sizeof(msg));
 	msg.cmd = CMD_CLK_SET_RATE;
-- 
2.28.0

Re: [PATCH] clk: tegra: bpmp: Clamp clock rates on requests

[Sivaram Nair]

On Wed, Oct 21, 2020 at 01:10:54PM +0300, Mikko Perttunen wrote:
> From: Sivaram Nair <sivaramn@nvidia.com>
> 
> BPMP firmware ABI expects the rate inputs in int64_t. However,
> tegra_bpmp_clk_round_rate() and tegra_bpmp_clk_set_rate() functions
> directly assign 'unsigned long' inputs to a int64_t value causing
> unexpected rounding errors.
> 
> Fix this by clipping the input rate to S64_MAX.
> 
> Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
> [mperttunen: slight cleanup]
> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
> ---
>  drivers/clk/tegra/clk-bpmp.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-bpmp.c b/drivers/clk/tegra/clk-bpmp.c
> index a66263b6490d..6ecf18f71c32 100644
> --- a/drivers/clk/tegra/clk-bpmp.c
> +++ b/drivers/clk/tegra/clk-bpmp.c
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /*
> - * Copyright (C) 2016 NVIDIA Corporation
> + * Copyright (C) 2016-2020 NVIDIA Corporation
>   */
>  
>  #include <linux/clk-provider.h>
> @@ -174,7 +174,7 @@ static long tegra_bpmp_clk_round_rate(struct clk_hw *hw, unsigned long rate,
>  	int err;
>  
>  	memset(&request, 0, sizeof(request));
> -	request.rate = rate;
> +	request.rate = min_t(u64, rate, S64_MAX);
>  
>  	memset(&msg, 0, sizeof(msg));
>  	msg.cmd = CMD_CLK_ROUND_RATE;
> @@ -256,7 +256,7 @@ static int tegra_bpmp_clk_set_rate(struct clk_hw *hw, unsigned long rate,
>  	struct tegra_bpmp_clk_message msg;
>  
>  	memset(&request, 0, sizeof(request));
> -	request.rate = rate;
> +	request.rate = min_t(u64, rate, S64_MAX);
>  
>  	memset(&msg, 0, sizeof(msg));
>  	msg.cmd = CMD_CLK_SET_RATE;
> -- 
> 2.28.0
> 

Reviewed-by: Sivaram Nair