From: Thara Gopinath <thara.gopinath@linaro.org>
To: Md Sadre Alam <mdalam@codeaurora.org>,
vkoul@kernel.org, corbet@lwn.net, agross@kernel.org,
bjorn.andersson@linaro.org, dan.j.williams@intel.com,
dmaengine@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Cc: sricharan@codeaurora.org
Subject: Re: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support
Date: Fri, 18 Dec 2020 22:35:17 -0500 [thread overview]
Message-ID: <6c85436d-e064-367e-736b-951af82256c8@linaro.org> (raw)
In-Reply-To: <1608215842-15381-1-git-send-email-mdalam@codeaurora.org>
On 12/17/20 9:37 AM, Md Sadre Alam wrote:
> This change will add support for LOCK & UNLOCK flag bit support
> on CMD descriptor.
>
> If DMA_PREP_LOCK flag passed in prep_slave_sg then requester of this
> transaction wanted to lock the DMA controller for this transaction so
> BAM driver should set LOCK bit for the HW descriptor.
>
> If DMA_PREP_UNLOCK flag passed in prep_slave_sg then requester of this
> transaction wanted to unlock the DMA controller.so BAM driver should set
> UNLOCK bit for the HW descriptor.
Hi,
This is a generic question. What is the point of LOCK/UNLOCK with
allocating LOCK groups to the individual dma channels? By default
doesn't all channels fall in the same group. This would mean that
a lock does not prevent the dma controller from not executing a
transaction on the other channels.
--
Warm Regards
Thara
>
> Signed-off-by: Md Sadre Alam <mdalam@codeaurora.org>
> ---
> Documentation/driver-api/dmaengine/provider.rst | 9 +++++++++
> drivers/dma/qcom/bam_dma.c | 9 +++++++++
> include/linux/dmaengine.h | 5 +++++
> 3 files changed, 23 insertions(+)
>
> diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
> index ddb0a81..d7516e2 100644
> --- a/Documentation/driver-api/dmaengine/provider.rst
> +++ b/Documentation/driver-api/dmaengine/provider.rst
> @@ -599,6 +599,15 @@ DMA_CTRL_REUSE
> - This flag is only supported if the channel reports the DMA_LOAD_EOT
> capability.
>
> +- DMA_PREP_LOCK
> +
> + - If set , the client driver tells DMA controller I am locking you for
> + this transcation.
> +
> +- DMA_PREP_UNLOCK
> +
> + - If set, the client driver will tells DMA controller I am releasing the lock
> +
> General Design Notes
> ====================
>
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 4eeb8bb..cdbe395 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -58,6 +58,8 @@ struct bam_desc_hw {
> #define DESC_FLAG_EOB BIT(13)
> #define DESC_FLAG_NWD BIT(12)
> #define DESC_FLAG_CMD BIT(11)
> +#define DESC_FLAG_LOCK BIT(10)
> +#define DESC_FLAG_UNLOCK BIT(9)
>
> struct bam_async_desc {
> struct virt_dma_desc vd;
> @@ -644,6 +646,13 @@ static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
>
> /* fill in temporary descriptors */
> desc = async_desc->desc;
> + if (flags & DMA_PREP_CMD) {
> + if (flags & DMA_PREP_LOCK)
> + desc->flags |= cpu_to_le16(DESC_FLAG_LOCK);
> + if (flags & DMA_PREP_UNLOCK)
> + desc->flags |= cpu_to_le16(DESC_FLAG_UNLOCK);
> + }
> +
> for_each_sg(sgl, sg, sg_len, i) {
> unsigned int remainder = sg_dma_len(sg);
> unsigned int curr_offset = 0;
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index dd357a7..79ccadb4 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -190,6 +190,9 @@ struct dma_interleaved_template {
> * transaction is marked with DMA_PREP_REPEAT will cause the new transaction
> * to never be processed and stay in the issued queue forever. The flag is
> * ignored if the previous transaction is not a repeated transaction.
> + * @DMA_PREP_LOCK: tell the driver that DMA HW engine going to be locked for this
> + * transaction , until not seen DMA_PREP_UNLOCK flag set.
> + * @DMA_PREP_UNLOCK: tell the driver to unlock the DMA HW engine.
> */
> enum dma_ctrl_flags {
> DMA_PREP_INTERRUPT = (1 << 0),
> @@ -202,6 +205,8 @@ enum dma_ctrl_flags {
> DMA_PREP_CMD = (1 << 7),
> DMA_PREP_REPEAT = (1 << 8),
> DMA_PREP_LOAD_EOT = (1 << 9),
> + DMA_PREP_LOCK = (1 << 10),
> + DMA_PREP_UNLOCK = (1 << 11),
> };
>
> /**
>
next prev parent reply other threads:[~2020-12-19 3:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 14:37 [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support Md Sadre Alam
2020-12-19 3:35 ` Thara Gopinath [this message]
2020-12-21 7:35 ` mdalam
2020-12-21 18:09 ` Thara Gopinath
2020-12-22 12:18 ` mdalam
2021-01-12 9:30 ` mdalam
2020-12-21 9:23 ` Vinod Koul
2020-12-21 17:33 ` mdalam
2021-01-12 9:31 ` mdalam
2021-01-12 10:10 ` Vinod Koul
2021-01-13 19:50 ` mdalam
2021-01-15 5:58 ` Vinod Koul
2021-01-18 3:51 ` mdalam
2021-01-19 16:45 ` Vinod Koul
2021-01-27 18:26 ` mdalam
2021-02-01 6:05 ` Vinod Koul
2021-02-01 6:22 ` mdalam
2021-02-01 6:43 ` Vinod Koul
2021-02-01 15:50 ` mdalam
2021-02-09 16:39 ` mdalam
2021-02-09 17:35 ` Bjorn Andersson
2021-02-11 4:01 ` mdalam
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