Re: [Patch v5 5/8] firmware: qcom: scm: Convert to streaming DMA APIS

Stephen Boyd
2016-06-02T23:26:06Z

On 05/12, Andy Gross wrote:
> This patch converts the Qualcomm SCM driver to use the streaming DMA APIs
> for communication buffers.

Yes, but why?

>
> Signed-off-by: Andy Gross <andy.gross@linaro.org>
> ---
> drivers/firmware/qcom_scm-32.c | 189 +++++++++++------------------------------
> drivers/firmware/qcom_scm.c | 6 +-
> drivers/firmware/qcom_scm.h | 10 ++-
> 3 files changed, 59 insertions(+), 146 deletions(-)
>
> diff --git a/drivers/firmware/qcom_scm-32.c b/drivers/firmware/qcom_scm-32.c
> index 4388d13..e92bf7a 100644
> --- a/drivers/firmware/qcom_scm-32.c
> +++ b/drivers/firmware/qcom_scm-32.c
> @@ -64,11 +63,11 @@ static DEFINE_MUTEX(qcom_scm_lock);
> *
> * ------------------- <--- struct qcom_scm_command
> * | command header |
> - * ------------------- <--- qcom_scm_get_command_buffer()
> + * ------------------- <--- buf[0]
> * | command buffer |
> - * ------------------- <--- struct qcom_scm_response and
> - * | response header | qcom_scm_command_to_response()
> - * ------------------- <--- qcom_scm_get_response_buffer()
> + * ------------------- <--- struct qcom_scm_response
> + * | response header |
> + * -------------------

You don't like my convenience functions? :) I always thought
qcom_scm_get_response_buffer() read better than

(void *)cmd->buf + le32_to_cpu(cmd->resp_hdr_offset);

> * | response buffer |
> * -------------------
> *
> @@ -96,79 +95,7 @@ struct qcom_scm_response {
> __le32 is_complete;
> };
>
> -
> -/**
> - * free_qcom_scm_command() - Free an SCM command
> - * @cmd: command to free
> - *
> - * Free an SCM command.
> - */
> -static inline void free_qcom_scm_command(struct qcom_scm_command *cmd)
> -{
> - kfree(cmd);
> -}
> -
> -/**
> - * qcom_scm_command_to_response() - Get a pointer to a qcom_scm_response
> - * @cmd: command
> - *
> - * Returns a pointer to a response for a command.
> - */
> -static inline struct qcom_scm_response *qcom_scm_command_to_response(
> - const struct qcom_scm_command *cmd)
> -{
> - return (void *)cmd + le32_to_cpu(cmd->resp_hdr_offset);
> -}
> -
> -/**
> - * qcom_scm_get_command_buffer() - Get a pointer to a command buffer
> - * @cmd: command
> - *
> - * Returns a pointer to the command buffer of a command.
> - */
> -static inline void *qcom_scm_get_command_buffer(const struct qcom_scm_command *cmd)
> -{
> - return (void *)cmd->buf;
> -}
> -
> -/**
> - * qcom_scm_get_response_buffer() - Get a pointer to a response buffer
> - * @rsp: response
> - *
> - * Returns a pointer to a response buffer of a response.
> - */
> -static inline void *qcom_scm_get_response_buffer(const struct qcom_scm_response *rsp)
> -{
> - return (void *)rsp + le32_to_cpu(rsp->buf_offset);
> -}

At the least the diff would be more concentrated on what really
is happening in this patch if we left these functions as is.

> -
> -static u32 smc(u32 cmd_addr)
> +static u32 smc(dma_addr_t cmd_addr)

Please leave this as u32, the interface doesn't support anything
wider here so we shouldn't let this change on LPAE.

> {
> int context_id;
> register u32 r0 asm("r0") = 1;
> @@ -192,45 +119,9 @@ static u32 smc(u32 cmd_addr)
> return r0;
> }
>
> -static int __qcom_scm_call(const struct qcom_scm_command *cmd)
> -{
> - int ret;
> - u32 cmd_addr = virt_to_phys(cmd);
> -
> - /*
> - * Flush the command buffer so that the secure world sees
> - * the correct data.
> - */
> - secure_flush_area(cmd, cmd->len);

Yay we should delete secure_flush_area() too.

> -
> - ret = smc(cmd_addr);
> - if (ret < 0)
> - ret = qcom_scm_remap_error(ret);
> -
> - return ret;
> -}
> -
> -
> @@ -143,7 +143,7 @@ int qcom_scm_hdcp_req(struct qcom_scm_hdcp_req *req, u32 req_cnt, u32 *resp)
> if (ret)
> return ret;
>
> - ret = __qcom_scm_hdcp_req(req, req_cnt, resp);
> + ret = __qcom_scm_hdcp_req(__scm->dev, req, req_cnt, resp);

Hmm maybe we should pass __scm instead of dev? Is there any
advantage to that?

> qcom_scm_clk_disable();
> return ret;
> }

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