linux-kernel - Re: [PATCH] dmaengine: tegra210-adma: fix transfer failure

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Date:   Thu, 20 Jun 2019 17:37:10 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Sameer Pujar <spujar@...dia.com>, <vkoul@...nel.org>,
        <dan.j.williams@...el.com>
CC:     <thierry.reding@...il.com>, <ldewangan@...dia.com>,
        <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: tegra210-adma: fix transfer failure


On 20/06/2019 17:15, Sameer Pujar wrote:
> From Tegra186 onwards OUTSTANDING_REQUESTS field is added in channel
> configuration register (bits 7:4). ADMA allows a maximum of 8 reads
> to source and that many writes to target memory be outstanding at any
> given point of time. If this field is not programmed, DMA transfers
> fail to happen.
> 
> Thus added 'ch_pending_req' member in chip data structure and the
> same is populated with maximum allowed pending requests. Since the
> field is not applicable to Tegra210, mentioned bit fields are unused
> and hence the member is initialized with 0.
> 
> Fixes: 433de642a76c ("dmaengine: tegra210-adma: add support for Tegra186/Tegra194")
> 
> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> ---
>  drivers/dma/tegra210-adma.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
> index 17ea4dd99..8d291cf 100644
> --- a/drivers/dma/tegra210-adma.c
> +++ b/drivers/dma/tegra210-adma.c
> @@ -96,6 +96,7 @@ struct tegra_adma;
>   * @ch_req_tx_shift: Register offset for AHUB transmit channel select.
>   * @ch_req_rx_shift: Register offset for AHUB receive channel select.
>   * @ch_base_offset: Register offset of DMA channel registers.
> + * @ch_pending_req: Outstaning DMA requests for a channel.
>   * @ch_fifo_ctrl: Default value for channel FIFO CTRL register.
>   * @ch_req_mask: Mask for Tx or Rx channel select.
>   * @ch_req_max: Maximum number of Tx or Rx channels available.
> @@ -109,6 +110,7 @@ struct tegra_adma_chip_data {
>  	unsigned int ch_req_tx_shift;
>  	unsigned int ch_req_rx_shift;
>  	unsigned int ch_base_offset;
> +	unsigned int ch_pending_req;
>  	unsigned int ch_fifo_ctrl;
>  	unsigned int ch_req_mask;
>  	unsigned int ch_req_max;
> @@ -613,6 +615,7 @@ static int tegra_adma_set_xfer_params(struct tegra_adma_chan *tdc,
>  			 ADMA_CH_CTRL_FLOWCTRL_EN;
>  	ch_regs->config |= cdata->adma_get_burst_config(burst_size);
>  	ch_regs->config |= ADMA_CH_CONFIG_WEIGHT_FOR_WRR(1);
> +	ch_regs->config |= cdata->ch_pending_req;
>  	ch_regs->fifo_ctrl = cdata->ch_fifo_ctrl;
>  	ch_regs->tc = desc->period_len & ADMA_CH_TC_COUNT_MASK;
>  
> @@ -797,6 +800,7 @@ static const struct tegra_adma_chip_data tegra210_chip_data = {
>  	.ch_req_tx_shift	= 28,
>  	.ch_req_rx_shift	= 24,
>  	.ch_base_offset		= 0,
> +	.ch_pending_req		= 0,
>  	.ch_fifo_ctrl		= TEGRA210_FIFO_CTRL_DEFAULT,
>  	.ch_req_mask		= 0xf,
>  	.ch_req_max		= 10,
> @@ -811,6 +815,7 @@ static const struct tegra_adma_chip_data tegra186_chip_data = {
>  	.ch_req_tx_shift	= 27,
>  	.ch_req_rx_shift	= 22,
>  	.ch_base_offset		= 0x10000,
> +	.ch_pending_req		= (8 << 4),

So given that this is a value and a shift, I think that we should add a
proper definition like we have for TEGRA186_FIFO_CTRL_DEFAULT below.

>  	.ch_fifo_ctrl		= TEGRA186_FIFO_CTRL_DEFAULT,
>  	.ch_req_mask		= 0x1f,
>  	.ch_req_max		= 20,
> 

Please group your patches into a series if you have more than one for a
given driver.

Cheers
Jon

-- 
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