Re: [PATCH v6] clk: qcom: Add lpass clock controller driver for SDM845

From: Taniya Das
Date: Tue Oct 09 2018 - 13:26:51 EST

Hello Stephen,

On 10/8/2018 8:14 AM, Stephen Boyd wrote:
Quoting Taniya Das (2018-10-04 05:02:26)
Add support for the lpass clock controller found on SDM845 based devices.
This would allow lpass peripheral loader drivers to control the clocks to
bring the subsystem out of reset.
LPASS clocks present on the global clock controller would be registered
with the clock framework based on the device tree flag. Also do not gate
these clocks if they are left unused.

Why not gate them? This statement states what the code is doing, not why
it's doing it which is the more crucial information that should be
described in the commit text. Also, please add a comment about it to the
code next to the flag.

I am concerned that it doesn't make any sense though, so probably it
shouldn't be marked as CLK_IGNORE_UNUSED and it's papering over some
other larger bug that needs to be fixed.


It does not have any bug, it is just that to access these lpass registers we would need the GCC lpass registers to be enabled. I would update the same in the commit text.

During clock late_init these clocks should not be accessed to check the clock status as they would result in unclocked access. The client would request these clocks in the correct order and it would not have any issue.



Signed-off-by: Taniya Das <tdas@xxxxxxxxxxxxxx>
---
diff --git a/drivers/clk/qcom/gcc-sdm845.c b/drivers/clk/qcom/gcc-sdm845.c
index 08d593e..6379b8b 100644
--- a/drivers/clk/qcom/gcc-sdm845.c
+++ b/drivers/clk/qcom/gcc-sdm845.c
@@ -3169,6 +3169,32 @@ enum {
},
};

+static struct clk_branch gcc_lpass_q6_axi_clk = {
+ .halt_reg = 0x47000,
+ .halt_check = BRANCH_HALT,
+ .clkr = {
+ .enable_reg = 0x47000,
+ .enable_mask = BIT(0),
+ .hw.init = &(struct clk_init_data){
+ .name = "gcc_lpass_q6_axi_clk",
+ .ops = &clk_branch2_ops,
+ },
+ },
+};
+
+static struct clk_branch gcc_lpass_sway_clk = {
+ .halt_reg = 0x47008,
+ .halt_check = BRANCH_HALT,
+ .clkr = {
+ .enable_reg = 0x47008,
+ .enable_mask = BIT(0),
+ .hw.init = &(struct clk_init_data){
+ .name = "gcc_lpass_sway_clk",
+ .ops = &clk_branch2_ops,
+ },
+ },
+};
+
static struct gdsc pcie_0_gdsc = {
.gdscr = 0x6b004,
.pd = {
@@ -3469,6 +3495,8 @@ enum {
[GCC_QSPI_CORE_CLK_SRC] = &gcc_qspi_core_clk_src.clkr,
[GCC_QSPI_CORE_CLK] = &gcc_qspi_core_clk.clkr,
[GCC_QSPI_CNOC_PERIPH_AHB_CLK] = &gcc_qspi_cnoc_periph_ahb_clk.clkr,
+ [GCC_LPASS_Q6_AXI_CLK] = NULL,
+ [GCC_LPASS_SWAY_CLK] = NULL,
};

static const struct qcom_reset_map gcc_sdm845_resets[] = {
@@ -3583,6 +3611,13 @@ static int gcc_sdm845_probe(struct platform_device *pdev)
if (ret)
return ret;

+ if (!of_property_read_bool(pdev->dev.of_node, "qcom,lpass-protected")) {
+ gcc_sdm845_clocks[GCC_LPASS_Q6_AXI_CLK] =
+ &gcc_lpass_q6_axi_clk.clkr;
+ gcc_sdm845_clocks[GCC_LPASS_SWAY_CLK] =
+ &gcc_lpass_sway_clk.clkr;
+ }
+
return qcom_cc_really_probe(pdev, &gcc_sdm845_desc, regmap);
}

diff --git a/drivers/clk/qcom/lpasscc-sdm845.c b/drivers/clk/qcom/lpasscc-sdm845.c
new file mode 100644
index 0000000..f7b9b0f
--- /dev/null
+++ b/drivers/clk/qcom/lpasscc-sdm845.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/bitops.h>

Is this needed?


Would check this.

+/* CLK_OFF would not toggle until LPASS is not out of reset */
+static struct clk_branch lpass_qdsp6ss_xo_clk = {
+ .halt_reg = 0x38,
+ .halt_check = BRANCH_HALT_SKIP,
+ .clkr = {
+ .enable_reg = 0x38,
+ .enable_mask = BIT(0),
+ .hw.init = &(struct clk_init_data){
+ .name = "lpass_qdsp6ss_xo_clk",
+ .flags = CLK_IGNORE_UNUSED,
+ .ops = &clk_branch2_ops,
+ },
+ },
+};
+
+/* CLK_OFF would not toggle until LPASS is not out of reset */

Move this comment next to BRANCH_HALT_SKIP please so we know what it
relates to.


Sure would take care in the next patch.

+static struct clk_branch lpass_qdsp6ss_sleep_clk = {
+ .halt_reg = 0x3c,
+ .halt_check = BRANCH_HALT_SKIP,
+ .clkr = {
+ .enable_reg = 0x3c,
+ .enable_mask = BIT(0),
+ .hw.init = &(struct clk_init_data){
+ .name = "lpass_qdsp6ss_sleep_clk",
+ .flags = CLK_IGNORE_UNUSED,
+ .ops = &clk_branch2_ops,
+ },
+ },
+};
+
+static int lpass_clocks_sdm845_probe(struct platform_device *pdev, int index,
+ const struct qcom_cc_desc *desc)
+{
+ struct regmap *regmap;
+ struct resource *res;
+ void __iomem *base;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, index);
+ base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(base))
+ return PTR_ERR(base);
+
+ regmap = devm_regmap_init_mmio(&pdev->dev, base, desc->config);
+ if (IS_ERR(regmap))
+ return PTR_ERR(regmap);

If this happens again in the future we should move this into the
common.c file and let qcom_cc_probe_index() exist.


Yes, I agree, could submit a patch to add the new function and then clean it up.

+
+ return qcom_cc_really_probe(pdev, desc, regmap);
+}
+
+/* LPASS CC clock controller */

Please remove this comment. It's useless.


Would take care in the next patch.

+static const struct of_device_id lpass_cc_sdm845_match_table[] = {
+ { .compatible = "qcom,sdm845-lpasscc" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, lpass_cc_sdm845_match_table);
+

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