[PATCH v2 7/9] clk: samsung: exynos850: Implement CMU_MFCMSCL domain

From: Sam Protsenko
Date: Tue Aug 09 2022 - 07:34:12 EST

Next message: Sam Protsenko: "[PATCH v2 9/9] arm64: dts: exynos: Add SysMMU nodes for Exynos850"
Previous message: Sam Protsenko: "[PATCH v2 8/9] arm64: dts: exynos: Add CMU_AUD, CMU_IS and CMU_MFCMSCL for Exynos850"
In reply to: Sam Protsenko: "[PATCH v2 8/9] arm64: dts: exynos: Add CMU_AUD, CMU_IS and CMU_MFCMSCL for Exynos850"
Next in thread: Krzysztof Kozlowski: "Re: [PATCH v2 7/9] clk: samsung: exynos850: Implement CMU_MFCMSCL domain"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

CMU_MFCMSCL clock domain provides clocks for MFC (Multi-Format Codec),
JPEG Codec and Scaler IP-cores. According to Exynos850 TRM, CMU_MFCMSCL
generates MFC, M2M, MCSC and JPEG clocks for BLK_MFCMSCL.

This patch adds next clocks:
- bus clocks in CMU_TOP for CMU_MFCMSCL
- all internal CMU_MFCMSCL clocks
- leaf clocks for MFCMSCL, TZPC (TrustZone Protection Controller),
JPEG codec, M2M (Memory-to-Memory), MCSC (Multi-Channel Scaler),
MFC (Multi-Format Codec), PPMU (Platform Performance Monitoring
Unit), SysMMU and SysReg

MFCMSCL related gate clocks in CMU_TOP were marked as CLK_IS_CRITICAL,
because:
1. All of those have to be enabled in order to read
/sys/kernel/debug/clk/clk_summary file
2. When some user driver (e.g. exynos-sysmmu) disables some derived
leaf clock, it can lead to CMU_TOP clocks disable, which then makes
the system hang. To prevent that, the CLK_IS_CRITICAL flag is used,
as CLK_IGNORE_UNUSED is not enough.

Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
---
Changes in v2:
- (none)

drivers/clk/samsung/clk-exynos850.c | 176 ++++++++++++++++++++++++++++
1 file changed, 176 insertions(+)

diff --git a/drivers/clk/samsung/clk-exynos850.c b/drivers/clk/samsung/clk-exynos850.c
index 18a36d58101e..541761e96aeb 100644
--- a/drivers/clk/samsung/clk-exynos850.c
+++ b/drivers/clk/samsung/clk-exynos850.c
@@ -43,6 +43,10 @@
#define CLK_CON_MUX_MUX_CLKCMU_IS_GDC 0x104c
#define CLK_CON_MUX_MUX_CLKCMU_IS_ITP 0x1050
#define CLK_CON_MUX_MUX_CLKCMU_IS_VRA 0x1054
+#define CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_JPEG 0x1058
+#define CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_M2M 0x105c
+#define CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MCSC 0x1060
+#define CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MFC 0x1064
#define CLK_CON_MUX_MUX_CLKCMU_PERI_BUS 0x1070
#define CLK_CON_MUX_MUX_CLKCMU_PERI_IP 0x1074
#define CLK_CON_MUX_MUX_CLKCMU_PERI_UART 0x1078
@@ -60,6 +64,10 @@
#define CLK_CON_DIV_CLKCMU_IS_GDC 0x1858
#define CLK_CON_DIV_CLKCMU_IS_ITP 0x185c
#define CLK_CON_DIV_CLKCMU_IS_VRA 0x1860
+#define CLK_CON_DIV_CLKCMU_MFCMSCL_JPEG 0x1864
+#define CLK_CON_DIV_CLKCMU_MFCMSCL_M2M 0x1868
+#define CLK_CON_DIV_CLKCMU_MFCMSCL_MCSC 0x186c
+#define CLK_CON_DIV_CLKCMU_MFCMSCL_MFC 0x1870
#define CLK_CON_DIV_CLKCMU_PERI_BUS 0x187c
#define CLK_CON_DIV_CLKCMU_PERI_IP 0x1880
#define CLK_CON_DIV_CLKCMU_PERI_UART 0x1884
@@ -83,6 +91,10 @@
#define CLK_CON_GAT_GATE_CLKCMU_IS_GDC 0x2054
#define CLK_CON_GAT_GATE_CLKCMU_IS_ITP 0x2058
#define CLK_CON_GAT_GATE_CLKCMU_IS_VRA 0x205c
+#define CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_JPEG 0x2060
+#define CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_M2M 0x2064
+#define CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MCSC 0x2068
+#define CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MFC 0x206c
#define CLK_CON_GAT_GATE_CLKCMU_PERI_BUS 0x2080
#define CLK_CON_GAT_GATE_CLKCMU_PERI_IP 0x2084
#define CLK_CON_GAT_GATE_CLKCMU_PERI_UART 0x2088
@@ -111,6 +123,10 @@ static const unsigned long top_clk_regs[] __initconst = {
CLK_CON_MUX_MUX_CLKCMU_IS_GDC,
CLK_CON_MUX_MUX_CLKCMU_IS_ITP,
CLK_CON_MUX_MUX_CLKCMU_IS_VRA,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_JPEG,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_M2M,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MCSC,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MFC,
CLK_CON_MUX_MUX_CLKCMU_PERI_BUS,
CLK_CON_MUX_MUX_CLKCMU_PERI_IP,
CLK_CON_MUX_MUX_CLKCMU_PERI_UART,
@@ -128,6 +144,10 @@ static const unsigned long top_clk_regs[] __initconst = {
CLK_CON_DIV_CLKCMU_IS_GDC,
CLK_CON_DIV_CLKCMU_IS_ITP,
CLK_CON_DIV_CLKCMU_IS_VRA,
+ CLK_CON_DIV_CLKCMU_MFCMSCL_JPEG,
+ CLK_CON_DIV_CLKCMU_MFCMSCL_M2M,
+ CLK_CON_DIV_CLKCMU_MFCMSCL_MCSC,
+ CLK_CON_DIV_CLKCMU_MFCMSCL_MFC,
CLK_CON_DIV_CLKCMU_PERI_BUS,
CLK_CON_DIV_CLKCMU_PERI_IP,
CLK_CON_DIV_CLKCMU_PERI_UART,
@@ -151,6 +171,10 @@ static const unsigned long top_clk_regs[] __initconst = {
CLK_CON_GAT_GATE_CLKCMU_IS_GDC,
CLK_CON_GAT_GATE_CLKCMU_IS_ITP,
CLK_CON_GAT_GATE_CLKCMU_IS_VRA,
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_JPEG,
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_M2M,
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MCSC,
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MFC,
CLK_CON_GAT_GATE_CLKCMU_PERI_BUS,
CLK_CON_GAT_GATE_CLKCMU_PERI_IP,
CLK_CON_GAT_GATE_CLKCMU_PERI_UART,
@@ -209,6 +233,15 @@ PNAME(mout_is_vra_p) = { "dout_shared0_div2", "dout_shared1_div2",
"dout_shared0_div3", "dout_shared1_div3" };
PNAME(mout_is_gdc_p) = { "dout_shared0_div2", "dout_shared1_div2",
"dout_shared0_div3", "dout_shared1_div3" };
+/* List of parent clocks for Muxes in CMU_TOP: for CMU_MFCMSCL */
+PNAME(mout_mfcmscl_mfc_p) = { "dout_shared1_div2", "dout_shared0_div3",
+ "dout_shared1_div3", "dout_shared0_div4" };
+PNAME(mout_mfcmscl_m2m_p) = { "dout_shared1_div2", "dout_shared0_div3",
+ "dout_shared1_div3", "dout_shared0_div4" };
+PNAME(mout_mfcmscl_mcsc_p) = { "dout_shared1_div2", "dout_shared0_div3",
+ "dout_shared1_div3", "dout_shared0_div4" };
+PNAME(mout_mfcmscl_jpeg_p) = { "dout_shared0_div3", "dout_shared1_div3",
+ "dout_shared0_div4", "dout_shared1_div4" };
/* List of parent clocks for Muxes in CMU_TOP: for CMU_PERI */
PNAME(mout_peri_bus_p) = { "dout_shared0_div4", "dout_shared1_div4" };
PNAME(mout_peri_uart_p) = { "oscclk", "dout_shared0_div4",
@@ -268,6 +301,16 @@ static const struct samsung_mux_clock top_mux_clks[] __initconst = {
MUX(CLK_MOUT_IS_GDC, "mout_is_gdc", mout_is_gdc_p,
CLK_CON_MUX_MUX_CLKCMU_IS_GDC, 0, 2),

+ /* MFCMSCL */
+ MUX(CLK_MOUT_MFCMSCL_MFC, "mout_mfcmscl_mfc", mout_mfcmscl_mfc_p,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MFC, 0, 2),
+ MUX(CLK_MOUT_MFCMSCL_M2M, "mout_mfcmscl_m2m", mout_mfcmscl_m2m_p,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_M2M, 0, 2),
+ MUX(CLK_MOUT_MFCMSCL_MCSC, "mout_mfcmscl_mcsc", mout_mfcmscl_mcsc_p,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_MCSC, 0, 2),
+ MUX(CLK_MOUT_MFCMSCL_JPEG, "mout_mfcmscl_jpeg", mout_mfcmscl_jpeg_p,
+ CLK_CON_MUX_MUX_CLKCMU_MFCMSCL_JPEG, 0, 2),
+
/* PERI */
MUX(CLK_MOUT_PERI_BUS, "mout_peri_bus", mout_peri_bus_p,
CLK_CON_MUX_MUX_CLKCMU_PERI_BUS, 0, 1),
@@ -332,6 +375,16 @@ static const struct samsung_div_clock top_div_clks[] __initconst = {
DIV(CLK_DOUT_IS_GDC, "dout_is_gdc", "gout_is_gdc",
CLK_CON_DIV_CLKCMU_IS_GDC, 0, 4),

+ /* MFCMSCL */
+ DIV(CLK_DOUT_MFCMSCL_MFC, "dout_mfcmscl_mfc", "gout_mfcmscl_mfc",
+ CLK_CON_DIV_CLKCMU_MFCMSCL_MFC, 0, 4),
+ DIV(CLK_DOUT_MFCMSCL_M2M, "dout_mfcmscl_m2m", "gout_mfcmscl_m2m",
+ CLK_CON_DIV_CLKCMU_MFCMSCL_M2M, 0, 4),
+ DIV(CLK_DOUT_MFCMSCL_MCSC, "dout_mfcmscl_mcsc", "gout_mfcmscl_mcsc",
+ CLK_CON_DIV_CLKCMU_MFCMSCL_MCSC, 0, 4),
+ DIV(CLK_DOUT_MFCMSCL_JPEG, "dout_mfcmscl_jpeg", "gout_mfcmscl_jpeg",
+ CLK_CON_DIV_CLKCMU_MFCMSCL_JPEG, 0, 4),
+
/* PERI */
DIV(CLK_DOUT_PERI_BUS, "dout_peri_bus", "gout_peri_bus",
CLK_CON_DIV_CLKCMU_PERI_BUS, 0, 4),
@@ -383,6 +436,17 @@ static const struct samsung_gate_clock top_gate_clks[] __initconst = {
GATE(CLK_GOUT_IS_GDC, "gout_is_gdc", "mout_is_gdc",
CLK_CON_GAT_GATE_CLKCMU_IS_GDC, 21, CLK_IS_CRITICAL, 0),

+ /* MFCMSCL */
+ /* TODO: These have to be always enabled to access CMU_MFCMSCL regs */
+ GATE(CLK_GOUT_MFCMSCL_MFC, "gout_mfcmscl_mfc", "mout_mfcmscl_mfc",
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MFC, 21, CLK_IS_CRITICAL, 0),
+ GATE(CLK_GOUT_MFCMSCL_M2M, "gout_mfcmscl_m2m", "mout_mfcmscl_m2m",
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_M2M, 21, CLK_IS_CRITICAL, 0),
+ GATE(CLK_GOUT_MFCMSCL_MCSC, "gout_mfcmscl_mcsc", "mout_mfcmscl_mcsc",
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_MCSC, 21, CLK_IS_CRITICAL, 0),
+ GATE(CLK_GOUT_MFCMSCL_JPEG, "gout_mfcmscl_jpeg", "mout_mfcmscl_jpeg",
+ CLK_CON_GAT_GATE_CLKCMU_MFCMSCL_JPEG, 21, CLK_IS_CRITICAL, 0),
+
/* PERI */
GATE(CLK_GOUT_PERI_BUS, "gout_peri_bus", "mout_peri_bus",
CLK_CON_GAT_GATE_CLKCMU_PERI_BUS, 21, 0, 0),
@@ -1148,6 +1212,115 @@ static const struct samsung_cmu_info is_cmu_info __initconst = {
.clk_name = "dout_is_bus",
};

+/* ---- CMU_MFCMSCL --------------------------------------------------------- */
+
+#define PLL_CON0_MUX_CLKCMU_MFCMSCL_JPEG_USER 0x0600
+#define PLL_CON0_MUX_CLKCMU_MFCMSCL_M2M_USER 0x0610
+#define PLL_CON0_MUX_CLKCMU_MFCMSCL_MCSC_USER 0x0620
+#define PLL_CON0_MUX_CLKCMU_MFCMSCL_MFC_USER 0x0630
+#define CLK_CON_DIV_DIV_CLK_MFCMSCL_BUSP 0x1800
+#define CLK_CON_GAT_CLK_MFCMSCL_CMU_MFCMSCL_PCLK 0x2000
+#define CLK_CON_GAT_GOUT_MFCMSCL_TZPC_PCLK 0x2038
+#define CLK_CON_GAT_GOUT_MFCMSCL_JPEG_ACLK 0x203c
+#define CLK_CON_GAT_GOUT_MFCMSCL_M2M_ACLK 0x2048
+#define CLK_CON_GAT_GOUT_MFCMSCL_MCSC_I_CLK 0x204c
+#define CLK_CON_GAT_GOUT_MFCMSCL_MFC_ACLK 0x2050
+#define CLK_CON_GAT_GOUT_MFCMSCL_PPMU_ACLK 0x2054
+#define CLK_CON_GAT_GOUT_MFCMSCL_PPMU_PCLK 0x2058
+#define CLK_CON_GAT_GOUT_MFCMSCL_SYSMMU_CLK_S1 0x2074
+#define CLK_CON_GAT_GOUT_MFCMSCL_SYSREG_PCLK 0x2078
+
+static const unsigned long mfcmscl_clk_regs[] __initconst = {
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_JPEG_USER,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_M2M_USER,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_MCSC_USER,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_MFC_USER,
+ CLK_CON_DIV_DIV_CLK_MFCMSCL_BUSP,
+ CLK_CON_GAT_CLK_MFCMSCL_CMU_MFCMSCL_PCLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_TZPC_PCLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_JPEG_ACLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_M2M_ACLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_MCSC_I_CLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_MFC_ACLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_PPMU_ACLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_PPMU_PCLK,
+ CLK_CON_GAT_GOUT_MFCMSCL_SYSMMU_CLK_S1,
+ CLK_CON_GAT_GOUT_MFCMSCL_SYSREG_PCLK,
+};
+
+/* List of parent clocks for Muxes in CMU_MFCMSCL */
+PNAME(mout_mfcmscl_mfc_user_p) = { "oscclk", "dout_mfcmscl_mfc" };
+PNAME(mout_mfcmscl_m2m_user_p) = { "oscclk", "dout_mfcmscl_m2m" };
+PNAME(mout_mfcmscl_mcsc_user_p) = { "oscclk", "dout_mfcmscl_mcsc" };
+PNAME(mout_mfcmscl_jpeg_user_p) = { "oscclk", "dout_mfcmscl_jpeg" };
+
+static const struct samsung_mux_clock mfcmscl_mux_clks[] __initconst = {
+ MUX(CLK_MOUT_MFCMSCL_MFC_USER, "mout_mfcmscl_mfc_user",
+ mout_mfcmscl_mfc_user_p,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_MFC_USER, 4, 1),
+ MUX(CLK_MOUT_MFCMSCL_M2M_USER, "mout_mfcmscl_m2m_user",
+ mout_mfcmscl_m2m_user_p,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_M2M_USER, 4, 1),
+ MUX(CLK_MOUT_MFCMSCL_MCSC_USER, "mout_mfcmscl_mcsc_user",
+ mout_mfcmscl_mcsc_user_p,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_MCSC_USER, 4, 1),
+ MUX(CLK_MOUT_MFCMSCL_JPEG_USER, "mout_mfcmscl_jpeg_user",
+ mout_mfcmscl_jpeg_user_p,
+ PLL_CON0_MUX_CLKCMU_MFCMSCL_JPEG_USER, 4, 1),
+};
+
+static const struct samsung_div_clock mfcmscl_div_clks[] __initconst = {
+ DIV(CLK_DOUT_MFCMSCL_BUSP, "dout_mfcmscl_busp", "mout_mfcmscl_mfc_user",
+ CLK_CON_DIV_DIV_CLK_MFCMSCL_BUSP, 0, 3),
+};
+
+static const struct samsung_gate_clock mfcmscl_gate_clks[] __initconst = {
+ /* TODO: Should be enabled in MFC driver */
+ GATE(CLK_GOUT_MFCMSCL_CMU_MFCMSCL_PCLK, "gout_mfcmscl_cmu_mfcmscl_pclk",
+ "dout_mfcmscl_busp", CLK_CON_GAT_CLK_MFCMSCL_CMU_MFCMSCL_PCLK,
+ 21, CLK_IGNORE_UNUSED, 0),
+ GATE(CLK_GOUT_MFCMSCL_TZPC_PCLK, "gout_mfcmscl_tzpc_pclk",
+ "dout_mfcmscl_busp", CLK_CON_GAT_GOUT_MFCMSCL_TZPC_PCLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_JPEG_ACLK, "gout_mfcmscl_jpeg_aclk",
+ "mout_mfcmscl_jpeg_user", CLK_CON_GAT_GOUT_MFCMSCL_JPEG_ACLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_M2M_ACLK, "gout_mfcmscl_m2m_aclk",
+ "mout_mfcmscl_m2m_user", CLK_CON_GAT_GOUT_MFCMSCL_M2M_ACLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_MCSC_CLK, "gout_mfcmscl_mcsc_clk",
+ "mout_mfcmscl_mcsc_user", CLK_CON_GAT_GOUT_MFCMSCL_MCSC_I_CLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_MFC_ACLK, "gout_mfcmscl_mfc_aclk",
+ "mout_mfcmscl_mfc_user", CLK_CON_GAT_GOUT_MFCMSCL_MFC_ACLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_PPMU_ACLK, "gout_mfcmscl_ppmu_aclk",
+ "mout_mfcmscl_mfc_user", CLK_CON_GAT_GOUT_MFCMSCL_PPMU_ACLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_PPMU_PCLK, "gout_mfcmscl_ppmu_pclk",
+ "dout_mfcmscl_busp", CLK_CON_GAT_GOUT_MFCMSCL_PPMU_PCLK,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_SYSMMU_CLK, "gout_mfcmscl_sysmmu_clk",
+ "mout_mfcmscl_mfc_user", CLK_CON_GAT_GOUT_MFCMSCL_SYSMMU_CLK_S1,
+ 21, 0, 0),
+ GATE(CLK_GOUT_MFCMSCL_SYSREG_PCLK, "gout_mfcmscl_sysreg_pclk",
+ "dout_mfcmscl_busp", CLK_CON_GAT_GOUT_MFCMSCL_SYSREG_PCLK,
+ 21, 0, 0),
+};
+
+static const struct samsung_cmu_info mfcmscl_cmu_info __initconst = {
+ .mux_clks = mfcmscl_mux_clks,
+ .nr_mux_clks = ARRAY_SIZE(mfcmscl_mux_clks),
+ .div_clks = mfcmscl_div_clks,
+ .nr_div_clks = ARRAY_SIZE(mfcmscl_div_clks),
+ .gate_clks = mfcmscl_gate_clks,
+ .nr_gate_clks = ARRAY_SIZE(mfcmscl_gate_clks),
+ .nr_clk_ids = MFCMSCL_NR_CLK,
+ .clk_regs = mfcmscl_clk_regs,
+ .nr_clk_regs = ARRAY_SIZE(mfcmscl_clk_regs),
+ .clk_name = "dout_mfcmscl_mfc",
+};
+
/* ---- CMU_PERI ------------------------------------------------------------ */

/* Register Offset definitions for CMU_PERI (0x10030000) */
@@ -1533,6 +1706,9 @@ static const struct of_device_id exynos850_cmu_of_match[] = {
}, {
.compatible = "samsung,exynos850-cmu-is",
.data = &is_cmu_info,
+ }, {
+ .compatible = "samsung,exynos850-cmu-mfcmscl",
+ .data = &mfcmscl_cmu_info,
}, {
.compatible = "samsung,exynos850-cmu-core",
.data = &core_cmu_info,
--
2.30.2

Next message: Sam Protsenko: "[PATCH v2 9/9] arm64: dts: exynos: Add SysMMU nodes for Exynos850"
Previous message: Sam Protsenko: "[PATCH v2 8/9] arm64: dts: exynos: Add CMU_AUD, CMU_IS and CMU_MFCMSCL for Exynos850"
In reply to: Sam Protsenko: "[PATCH v2 8/9] arm64: dts: exynos: Add CMU_AUD, CMU_IS and CMU_MFCMSCL for Exynos850"
Next in thread: Krzysztof Kozlowski: "Re: [PATCH v2 7/9] clk: samsung: exynos850: Implement CMU_MFCMSCL domain"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]