linux-kernel - Re: [PATCH 3/7] soc: qcom: geni: Add support for gpi dma

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Date:   Mon, 11 Jan 2021 09:40:55 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>, Wolfram Sang <wsa@...nel.org>,
        linux-arm-msm@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        linux-spi@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] soc: qcom: geni: Add support for gpi dma

On Mon 11 Jan 09:16 CST 2021, Vinod Koul wrote:

> GPI DMA is one of the DMA modes supported on geni, this adds support to
> enable that mode
> 
> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> ---
>  drivers/soc/qcom/qcom-geni-se.c | 39 ++++++++++++++++++++++++++++++++-
>  include/linux/qcom-geni-se.h    |  4 ++++
>  2 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
> index a3868228ea05..db44dc32e049 100644
> --- a/drivers/soc/qcom/qcom-geni-se.c
> +++ b/drivers/soc/qcom/qcom-geni-se.c
> @@ -310,6 +310,39 @@ static void geni_se_select_dma_mode(struct geni_se *se)
>  		writel_relaxed(val, se->base + SE_GENI_DMA_MODE_EN);
>  }
>  
> +static int geni_se_select_gpi_mode(struct geni_se *se)

This doesn't return any information and the return value isn't looked
at, please make it void.

> +{
> +	unsigned int geni_dma_mode = 0;
> +	unsigned int gpi_event_en = 0;
> +	unsigned int common_geni_m_irq_en = 0;
> +	unsigned int common_geni_s_irq_en = 0;

These could certainly be given a shorter name.

None of them needs to be initialized, first access in all cases are
assignments.

> +
> +	common_geni_m_irq_en = readl_relaxed(se->base + SE_GENI_M_IRQ_EN);
> +	common_geni_s_irq_en = readl_relaxed(se->base + SE_GENI_S_IRQ_EN);
> +	common_geni_m_irq_en &=
> +			~(M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN |
> +			M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN);
> +	common_geni_s_irq_en &= ~S_CMD_DONE_EN;
> +	geni_dma_mode = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
> +	gpi_event_en = readl_relaxed(se->base + SE_GSI_EVENT_EN);
> +
> +	geni_dma_mode |= GENI_DMA_MODE_EN;
> +	gpi_event_en |= (DMA_RX_EVENT_EN | DMA_TX_EVENT_EN |
> +				GENI_M_EVENT_EN | GENI_S_EVENT_EN);

Please reorder these so that you do
	readl(m)
	mask out bits of m

	readl(s)
	mask out bits of s

	...

> +
> +	writel_relaxed(0, se->base + SE_IRQ_EN);
> +	writel_relaxed(common_geni_s_irq_en, se->base + SE_GENI_S_IRQ_EN);
> +	writel_relaxed(common_geni_m_irq_en, se->base + SE_GENI_M_IRQ_EN);
> +	writel_relaxed(0xFFFFFFFF, se->base + SE_GENI_M_IRQ_CLEAR);

Lowercase hex digits please.

> +	writel_relaxed(0xFFFFFFFF, se->base + SE_GENI_S_IRQ_CLEAR);
> +	writel_relaxed(0xFFFFFFFF, se->base + SE_DMA_TX_IRQ_CLR);
> +	writel_relaxed(0xFFFFFFFF, se->base + SE_DMA_RX_IRQ_CLR);
> +	writel_relaxed(geni_dma_mode, se->base + SE_GENI_DMA_MODE_EN);
> +	writel_relaxed(gpi_event_en, se->base + SE_GSI_EVENT_EN);

Why is this driver using _relaxed accessors exclusively? Why are you
using _relaxed versions?

And wouldn't it be suitable to have a wmb() before the "dma mode enable"
and "event enable" at least? (I.e. use writel() instead)

Regards,
Bjorn

> +
> +	return 0;
> +}
> +
>  /**
>   * geni_se_select_mode() - Select the serial engine transfer mode
>   * @se:		Pointer to the concerned serial engine.
> @@ -317,7 +350,8 @@ static void geni_se_select_dma_mode(struct geni_se *se)
>   */
>  void geni_se_select_mode(struct geni_se *se, enum geni_se_xfer_mode mode)
>  {
> -	WARN_ON(mode != GENI_SE_FIFO && mode != GENI_SE_DMA);
> +	WARN_ON(mode != GENI_SE_FIFO && mode != GENI_SE_DMA &&
> +		mode != GENI_GPI_DMA);
>  
>  	switch (mode) {
>  	case GENI_SE_FIFO:
> @@ -326,6 +360,9 @@ void geni_se_select_mode(struct geni_se *se, enum geni_se_xfer_mode mode)
>  	case GENI_SE_DMA:
>  		geni_se_select_dma_mode(se);
>  		break;
> +	case GENI_GPI_DMA:
> +		geni_se_select_gpi_mode(se);
> +		break;
>  	case GENI_SE_INVALID:
>  	default:
>  		break;
> diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h
> index cb4e40908f9f..12003a6cb133 100644
> --- a/include/linux/qcom-geni-se.h
> +++ b/include/linux/qcom-geni-se.h
> @@ -12,6 +12,7 @@
>  enum geni_se_xfer_mode {
>  	GENI_SE_INVALID,
>  	GENI_SE_FIFO,
> +	GENI_GPI_DMA,
>  	GENI_SE_DMA,
>  };
>  
> @@ -123,6 +124,9 @@ struct geni_se {
>  #define CLK_DIV_MSK			GENMASK(15, 4)
>  #define CLK_DIV_SHFT			4
>  
> +/* GENI_IF_DISABLE_RO fields */
> +#define FIFO_IF_DISABLE			(BIT(0))
> +
>  /* GENI_FW_REVISION_RO fields */
>  #define FW_REV_PROTOCOL_MSK		GENMASK(15, 8)
>  #define FW_REV_PROTOCOL_SHFT		8
> -- 
> 2.26.2
>