[PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands

[PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands

[Douglas Anderson]

Writing the command is the final step in kicking off a transfer.
Let's use writel() to ensure that any other memory accesses are done
before the command kicks off.  It's expected that this is mostly
relevant if we're in DMA mode but since it doesn't appear to regress
performance in a measurable way [1] even in PIO mode and it's easier
to reason about then let's just always use it.

NOTE: this patch came about due to code inspection.  No actual
problems were observed that this patch fixes.

[1] Tested by timing "flashrom -p ec" on a Chromebook which stresses
GENI SPI a lot.

Suggested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 include/linux/qcom-geni-se.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h
index dd464943f717..f50c73be1428 100644
--- a/include/linux/qcom-geni-se.h
+++ b/include/linux/qcom-geni-se.h
@@ -262,7 +262,7 @@ static inline void geni_se_setup_m_cmd(struct geni_se *se, u32 cmd, u32 params)
 	u32 m_cmd;
 
 	m_cmd = (cmd << M_OPCODE_SHFT) | (params & M_PARAMS_MSK);
-	writel_relaxed(m_cmd, se->base + SE_GENI_M_CMD0);
+	writel(m_cmd, se->base + SE_GENI_M_CMD0);
 }
 
 /**
@@ -282,7 +282,7 @@ static inline void geni_se_setup_s_cmd(struct geni_se *se, u32 cmd, u32 params)
 	s_cmd &= ~(S_OPCODE_MSK | S_PARAMS_MSK);
 	s_cmd |= (cmd << S_OPCODE_SHFT);
 	s_cmd |= (params & S_PARAMS_MSK);
-	writel_relaxed(s_cmd, se->base + SE_GENI_S_CMD0);
+	writel(s_cmd, se->base + SE_GENI_S_CMD0);
 }
 
 /**
-- 
2.28.0.rc0.142.g3c755180ce-goog

Re: [PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands

[Stephen Boyd]

Quoting Douglas Anderson (2020-07-22 15:01:20)
> Writing the command is the final step in kicking off a transfer.
> Let's use writel() to ensure that any other memory accesses are done
> before the command kicks off.  It's expected that this is mostly
> relevant if we're in DMA mode but since it doesn't appear to regress
> performance in a measurable way [1] even in PIO mode and it's easier
> to reason about then let's just always use it.
> 
> NOTE: this patch came about due to code inspection.  No actual
> problems were observed that this patch fixes.
> 
> [1] Tested by timing "flashrom -p ec" on a Chromebook which stresses
> GENI SPI a lot.
> 
> Suggested-by: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Re: [PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands

[Akash Asthana]

On 7/23/2020 3:31 AM, Douglas Anderson wrote:
> Writing the command is the final step in kicking off a transfer.
> Let's use writel() to ensure that any other memory accesses are done
> before the command kicks off.  It's expected that this is mostly
> relevant if we're in DMA mode but since it doesn't appear to regress
> performance in a measurable way [1] even in PIO mode and it's easier
> to reason about then let's just always use it.
>
> NOTE: this patch came about due to code inspection.  No actual
> problems were observed that this patch fixes.
>
> [1] Tested by timing "flashrom -p ec" on a Chromebook which stresses
> GENI SPI a lot.
>
> Suggested-by: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
Reviewed-by: Akash Asthana <akashast@codeaurora.org>

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project

Re: [PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands

[Mukesh, Savaliya]

On 7/23/2020 3:31 AM, Douglas Anderson wrote:
> Writing the command is the final step in kicking off a transfer.
> Let's use writel() to ensure that any other memory accesses are done
> before the command kicks off.  It's expected that this is mostly
> relevant if we're in DMA mode but since it doesn't appear to regress
> performance in a measurable way [1] even in PIO mode and it's easier
> to reason about then let's just always use it.
>
> NOTE: this patch came about due to code inspection.  No actual
> problems were observed that this patch fixes.
>
> [1] Tested by timing "flashrom -p ec" on a Chromebook which stresses
> GENI SPI a lot.
>
> Suggested-by: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
> ---
>
>   include/linux/qcom-geni-se.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h
> index dd464943f717..f50c73be1428 100644
> --- a/include/linux/qcom-geni-se.h
> +++ b/include/linux/qcom-geni-se.h
> @@ -262,7 +262,7 @@ static inline void geni_se_setup_m_cmd(struct geni_se *se, u32 cmd, u32 params)
>   	u32 m_cmd;
>   
>   	m_cmd = (cmd << M_OPCODE_SHFT) | (params & M_PARAMS_MSK);
> -	writel_relaxed(m_cmd, se->base + SE_GENI_M_CMD0);
> +	writel(m_cmd, se->base + SE_GENI_M_CMD0);
>   }
>   
>   /**
> @@ -282,7 +282,7 @@ static inline void geni_se_setup_s_cmd(struct geni_se *se, u32 cmd, u32 params)
>   	s_cmd &= ~(S_OPCODE_MSK | S_PARAMS_MSK);
>   	s_cmd |= (cmd << S_OPCODE_SHFT);
>   	s_cmd |= (params & S_PARAMS_MSK);
> -	writel_relaxed(s_cmd, se->base + SE_GENI_S_CMD0);
> +	writel(s_cmd, se->base + SE_GENI_S_CMD0);
>   }
>   
>   /**