linux-kernel - Re: [PATCH V1] i2c: tegra: Fix Maximum transfer size

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Date:   Wed, 2 Jan 2019 22:05:10 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>,
        "talho@...dia.com" <talho@...dia.com>
CC:     "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH V1] i2c: tegra: Fix Maximum transfer size

On 2019-01-02 22:48, Sowjanya Komatineni wrote:
> Tegra194 supports maximum 64K Bytes transfer per packet.
> Tegra186 and prior supports maximum 4K Bytes transfer per packet.
> 
> This patch fixes this payload difference between Tegra194 and prior
> tegra chipsets.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 437294ea2f0a..0c08ed8b6c94 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -167,6 +167,7 @@ struct tegra_i2c_hw_feature {
>  	bool has_multi_master_mode;
>  	bool has_slcg_override_reg;
>  	bool has_mst_fifo;
> +	struct i2c_adapter_quirks *quirks;

This could perhaps be a pointer to const?

>  };
>  
>  /**
> @@ -833,6 +834,12 @@ static const struct i2c_adapter_quirks tegra_i2c_quirks = {
>  	.max_write_len = 4096,
>  };
>  
> +static const struct i2c_adapter_quirks tegra194_i2c_quirks = {
> +	.flags = I2C_AQ_NO_ZERO_LEN,

This is not mentioned in the commit message and the flag is not present in
the old struct tegra_i2c_quirks above. Are you trying to sneak changes past
the maintainers, or was the change simply not intentional?

> +	.max_read_len = 65536,
> +	.max_write_len = 65536,

Those are highly dubious when .max_read_len and .max_write_len are of type
u16. I bet you could just remove them.

Cheers,
Peter

> +};
> +
>  static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>  	.has_continue_xfer_support = false,
>  	.has_per_pkt_xfer_complete_irq = false,
> @@ -844,6 +851,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>  	.has_multi_master_mode = false,
>  	.has_slcg_override_reg = false,
>  	.has_mst_fifo = false,
> +	.quirks = &tegra_i2c_quirks,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -857,6 +865,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>  	.has_multi_master_mode = false,
>  	.has_slcg_override_reg = false,
>  	.has_mst_fifo = false,
> +	.quirks = &tegra_i2c_quirks,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
> @@ -870,6 +879,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
>  	.has_multi_master_mode = false,
>  	.has_slcg_override_reg = false,
>  	.has_mst_fifo = false,
> +	.quirks = &tegra_i2c_quirks,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
> @@ -883,6 +893,7 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
>  	.has_multi_master_mode = false,
>  	.has_slcg_override_reg = true,
>  	.has_mst_fifo = false,
> +	.quirks = &tegra_i2c_quirks,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> @@ -896,6 +907,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
>  	.has_multi_master_mode = true,
>  	.has_slcg_override_reg = true,
>  	.has_mst_fifo = false,
> +	.quirks = &tegra_i2c_quirks,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> @@ -909,6 +921,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
>  	.has_multi_master_mode = true,
>  	.has_slcg_override_reg = true,
>  	.has_mst_fifo = true,
> +	.quirks = &tegra194_i2c_quirks,
>  };
>  
>  /* Match table for of_platform binding */
> @@ -960,7 +973,6 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  	i2c_dev->base = base;
>  	i2c_dev->div_clk = div_clk;
>  	i2c_dev->adapter.algo = &tegra_i2c_algo;
> -	i2c_dev->adapter.quirks = &tegra_i2c_quirks;
>  	i2c_dev->irq = irq;
>  	i2c_dev->cont_id = pdev->id;
>  	i2c_dev->dev = &pdev->dev;
> @@ -976,6 +988,8 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  	i2c_dev->hw = of_device_get_match_data(&pdev->dev);
>  	i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node,
>  						  "nvidia,tegra20-i2c-dvc");
> +	i2c_dev->adapter.quirks = i2c_dev->hw->quirks;
> +
>  	init_completion(&i2c_dev->msg_complete);
>  	spin_lock_init(&i2c_dev->xfer_lock);
>  
>