linux-kernel - Re: [PATCH V10 4/5] i2c: tegra: update transfer timeout

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Message-ID: <3c51edfb-ca40-b696-db03-bf73677f06fd@gmail.com>
Date:   Tue, 5 Feb 2019 09:08:13 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com,
        mkarthik@...dia.com, smohammed@...dia.com, talho@...dia.com
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH V10 4/5] i2c: tegra: update transfer timeout

05.02.2019 4:29, Sowjanya Komatineni пишет:
> Tegra194 allows max of 64K bytes and Tegra186 and prior allows
> max of 4K bytes of transfer per packet.
> 
> one sec timeout is not enough for transfers more than 10K bytes
> at STD bus rate.
> 
> This patch updates I2C transfer timeout based on the transfer size
> and I2C bus rate to allow enough time during max transfer size at
> lower bus speed.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> Acked-by: Thierry Reding <treding@...dia.com>
> Reviewed-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  [V10] : Reduced the timeout for bus clear operation
> 	Added adapter timeout to cover worst case transfer rate (max transfer
> 	size at STD speed) incase if ARB LOST happens during middle/end of 
> 	the transaction.
>  [V9] : Rebased to 5.0-rc4
> 	Minor updates for readability of xfer time
>  [V8] : Added comment with explaination of xfer time calculation
>  [V5/V6/V7] : Same as V4
>  [V4] : V4 series includes bus clear support and this patch is updated with
> 	fixed timeout of 1sec for bus clear operation.
>  [V3] : Same as V2
>  [V2] : Added this patch in V2 series to allow enough time for data transfer
> 	to happen.
> 	This patch has dependency with DMA patch as TEGRA_I2C_TIMEOUT define
> 	takes argument with this patch.
> 
>  drivers/i2c/busses/i2c-tegra.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 658cf01e3f59..341475204cb6 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -25,7 +25,6 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/reset.h>
>  
> -#define TEGRA_I2C_TIMEOUT (msecs_to_jiffies(1000))
>  #define BYTES_PER_FIFO_WORD 4
>  
>  #define I2C_CNFG				0x000
> @@ -936,8 +935,9 @@ static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev)
>  		i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG);
>  		tegra_i2c_unmask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE);
>  
> -		time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> -							TEGRA_I2C_TIMEOUT);
> +		time_left = wait_for_completion_timeout(
> +						&i2c_dev->msg_complete,
> +						msecs_to_jiffies(50));
>  		if (time_left == 0) {
>  			dev_err(i2c_dev->dev, "timed out for bus clear\n");
>  			return -ETIMEDOUT;
> @@ -964,6 +964,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  	u32 *buffer = NULL;
>  	int err = 0;
>  	bool dma = false;
> +	u16 xfer_time = 100;
>  
>  	tegra_i2c_flush_fifos(i2c_dev);
>  
> @@ -982,6 +983,13 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  	dma = (xfer_size > I2C_PIO_MODE_MAX_LEN) && i2c_dev->dma_buf;
>  	i2c_dev->is_curr_dma_xfer = dma;
>  
> +	/*
> +	 * Transfer time in mSec = Total bits / transfer rate
> +	 * Total bits = 9 bits per byte (including ACK bit) + Start & stop bits
> +	 */
> +	xfer_time += DIV_ROUND_CLOSEST(((xfer_size * 9) + 2) * MSEC_PER_SEC,
> +					i2c_dev->bus_clk_rate);
> +
>  	spin_lock_irqsave(&i2c_dev->xfer_lock, flags);
>  
>  	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
> @@ -1089,7 +1097,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  
>  		time_left = wait_for_completion_timeout(
>  						&i2c_dev->dma_complete,
> -						TEGRA_I2C_TIMEOUT);
> +						msecs_to_jiffies(xfer_time));
>  
>  		if (time_left == 0) {
>  			dev_err(i2c_dev->dev, "DMA transfer timeout\n");
> @@ -1110,8 +1118,9 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  		}
>  	}
>  
> -	time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> -						TEGRA_I2C_TIMEOUT);
> +	time_left = wait_for_completion_timeout(
> +					&i2c_dev->msg_complete,
> +					msecs_to_jiffies(xfer_time));
>  	tegra_i2c_mask_irq(i2c_dev, int_mask);
>  
>  	if (time_left == 0) {
> @@ -1367,6 +1376,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  	i2c_dev->div_clk = div_clk;
>  	i2c_dev->adapter.algo = &tegra_i2c_algo;
>  	i2c_dev->adapter.retries = 1;
> +	i2c_dev->adapter.timeout = msecs_to_jiffies(6 * MSEC_PER_SEC);

There is a "HZ" constant in kernel which is equal to a number of jiffies per second. It's a common practice to use it where appropriate, in this case it will be:

	i2c_dev->adapter.timeout = 6 * HZ;

>  	i2c_dev->irq = irq;
>  	i2c_dev->cont_id = pdev->id;
>  	i2c_dev->dev = &pdev->dev;
>