Re: [PATCH v4] remoteproc: mediatek: Fix side effect of mt8195 sram power on

Il 16/03/22 17:34, Mathieu Poirier ha scritto:

Good morning,

On Wed, Mar 16, 2022 at 11:11:17AM +0800, Tinghan Shen wrote:

quoted

The definition of L1TCM_SRAM_PDN bits on mt8195 is different to mt8192.

L1TCM_SRAM_PDN bits[3:0] control the power of mt8195 L1TCM SRAM.

L1TCM_SRAM_PDN bits[7:4] control the access path to EMI for SCP.
These bits have to be powered on to allow EMI access for SCP.

Bits[7:4] also affect audio DSP because audio DSP and SCP are
placed on the same hardware bus. If SCP cannot access EMI, audio DSP is
blocked too.

L1TCM_SRAM_PDN bits[31:8] are not used.

This fix removes modification of bits[7:4] when power on/off mt8195 SCP
L1TCM. It's because the modification introduces a short period of time
blocking audio DSP to access EMI. This was not a problem until we have
to load both SCP module and audio DSP module. audio DSP needs to access
EMI because it has source/data on DRAM. Audio DSP will have unexpected
behavior when it accesses EMI and the SCP driver blocks the EMI path at
the same time.

Fixes: 79111df414fc ("remoteproc: mediatek: Support mt8195 scp")
Signed-off-by: Tinghan Shen <redacted>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
---
v4: add Fixes and Reviewed-by tags
v3: fix build error
v2: apply comments about macro definition and function calls
---
  drivers/remoteproc/mtk_common.h |  2 ++
  drivers/remoteproc/mtk_scp.c    | 67 +++++++++++++++++++++++++++++++----------
  2 files changed, 53 insertions(+), 16 deletions(-)

diff --git a/drivers/remoteproc/mtk_common.h b/drivers/remoteproc/mtk_common.h
index 5ff3867c72f3..ff954a06637c 100644
--- a/drivers/remoteproc/mtk_common.h
+++ b/drivers/remoteproc/mtk_common.h

@@ -51,6 +51,8 @@
  #define MT8192_CORE0_WDT_IRQ		0x10030
  #define MT8192_CORE0_WDT_CFG		0x10034
  
+#define MT8195_L1TCM_SRAM_PDN_RESERVED_RSI_BITS		GENMASK(7, 4)
+
  #define SCP_FW_VER_LEN			32
  #define SCP_SHARE_BUFFER_SIZE		288
  

diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index 36e48cf58ed6..5f686fe09203 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c

@@ -365,22 +365,22 @@ static int mt8183_scp_before_load(struct mtk_scp *scp)
  	return 0;
  }
  
-static void mt8192_power_on_sram(void __iomem *addr)
+static void scp_sram_power_on(void __iomem *addr, u32 reserved_mask)

Why is @reserved_mask needed?  It is not described in the changelong and as far
as I can see in this patchset the parameter is always set to '0', which has no
effect on the mask that gets generated.

Hello Mathieu,
the @reserved_mask is explained in perhaps not very very clear terms, meaning
that he's not explicitly saying the name of the new param, but that's it:

"This fix removes modification of bits[7:4] when power on/off mt8195 SCP
L1TCM."

....and it's actually being used, check below....

Thanks,
Mathieu

quoted

  {
  	int i;
  
  	for (i = 31; i >= 0; i--)
-		writel(GENMASK(i, 0), addr);
+		writel(GENMASK(i, 0) & ~reserved_mask, addr);
  	writel(0, addr);
  }
  
-static void mt8192_power_off_sram(void __iomem *addr)
+static void scp_sram_power_off(void __iomem *addr, u32 reserved_mask)

...snip...

quoted

+static int mt8195_scp_before_load(struct mtk_scp *scp)
+{
+	/* clear SPM interrupt, SCP2SPM_IPC_CLR */
+	writel(0xff, scp->reg_base + MT8192_SCP2SPM_IPC_CLR);
+
+	writel(1, scp->reg_base + MT8192_CORE0_SW_RSTN_SET);
+
+	/* enable SRAM clock */
+	scp_sram_power_on(scp->reg_base + MT8192_L2TCM_SRAM_PD_0, 0);
+	scp_sram_power_on(scp->reg_base + MT8192_L2TCM_SRAM_PD_1, 0);
+	scp_sram_power_on(scp->reg_base + MT8192_L2TCM_SRAM_PD_2, 0);

quoted

+	scp_sram_power_on(scp->reg_base + MT8192_L1TCM_SRAM_PDN,
+			  MT8195_L1TCM_SRAM_PDN_RESERVED_RSI_BITS);

here				^^^^^^^^^^^^

quoted

+	scp_sram_power_on(scp->reg_base + MT8192_CPU0_SRAM_PD, 0);
  
  	/* enable MPU for all memory regions */
  	writel(0xff, scp->reg_base + MT8192_CORE0_MEM_ATT_PREDEF);

...snip...

quoted

+
+static void mt8195_scp_stop(struct mtk_scp *scp)
+{
+	/* Disable SRAM clock */
+	scp_sram_power_off(scp->reg_base + MT8192_L2TCM_SRAM_PD_0, 0);
+	scp_sram_power_off(scp->reg_base + MT8192_L2TCM_SRAM_PD_1, 0);
+	scp_sram_power_off(scp->reg_base + MT8192_L2TCM_SRAM_PD_2, 0);
+	scp_sram_power_off(scp->reg_base + MT8192_L1TCM_SRAM_PDN,
+			   MT8195_L1TCM_SRAM_PDN_RESERVED_RSI_BITS);

and here 			^^^^^^^^

quoted

+	scp_sram_power_off(scp->reg_base + MT8192_CPU0_SRAM_PD, 0);
  

Cheers,
Angelo

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