From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: <linux-arch@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <arnd@arndb.de>, <arc-linux-dev@synopsys.com>,
Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: [PATCH 23/28] ARCv2: SLC: Handle explcit flush for DMA ops (w/o IO-coherency)
Date: Tue, 9 Jun 2015 17:18:23 +0530 [thread overview]
Message-ID: <1433850508-26317-24-git-send-email-vgupta@synopsys.com> (raw)
In-Reply-To: <1433850508-26317-1-git-send-email-vgupta@synopsys.com>
L2 cache on ARCHS processors is called SLC (System Level Cache)
For working DMA (in absence of hardware assisted IO Coherency) we need
to manage SLC explicitly when buffers transition between cpu and
controllers.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/include/asm/cache.h | 11 ++++++++
arch/arc/mm/cache.c | 64 ++++++++++++++++++++++++++++++++++++++++++--
arch/arc/mm/dma.c | 12 +++++++++
3 files changed, 85 insertions(+), 2 deletions(-)
diff --git a/arch/arc/include/asm/cache.h b/arch/arc/include/asm/cache.h
index d21c76d6b054..d67345d3e2d4 100644
--- a/arch/arc/include/asm/cache.h
+++ b/arch/arc/include/asm/cache.h
@@ -82,5 +82,16 @@ extern void read_decode_cache_bcr(void);
/*System-level cache (L2 cache) related Auxiliary registers */
#define ARC_REG_SLC_CFG 0x901
+#define ARC_REG_SLC_CTRL 0x903
+#define ARC_REG_SLC_FLUSH 0x904
+#define ARC_REG_SLC_INVALIDATE 0x905
+#define ARC_REG_SLC_RGN_START 0x914
+#define ARC_REG_SLC_RGN_END 0x916
+
+/* Bit val in SLC_CONTROL */
+#define SLC_CTRL_IM 0x040
+#define SLC_CTRL_DISABLE 0x001
+#define SLC_CTRL_BUSY 0x100
+#define SLC_CTRL_RGN_OP_INV 0x200
#endif /* _ASM_CACHE_H */
diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 0eaaee60fd0b..b29d62ed4f7e 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -21,6 +21,8 @@
#include <asm/cachectl.h>
#include <asm/setup.h>
+static int l2_line_sz;
+
void (*_cache_line_loop_ic_fn)(unsigned long paddr, unsigned long vaddr,
unsigned long sz, const int cacheop);
@@ -120,13 +122,16 @@ dc_chk:
p_dc->ver = dbcr.ver;
slc_chk:
+ if (!is_isa_arcv2())
+ return;
+
p_slc = &cpuinfo_arc700[cpu].slc;
READ_BCR(ARC_REG_SLC_BCR, sbcr);
if (sbcr.ver) {
READ_BCR(ARC_REG_SLC_CFG, slc_cfg);
p_slc->ver = sbcr.ver;
p_slc->sz_k = 128 << slc_cfg.sz;
- p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
+ l2_line_sz = p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
}
}
@@ -460,6 +465,53 @@ static void __ic_line_inv_vaddr(unsigned long paddr, unsigned long vaddr,
#endif /* CONFIG_ARC_HAS_ICACHE */
+noinline void slc_op(unsigned long paddr, unsigned long sz, const int op)
+{
+#ifdef CONFIG_ISA_ARCV2
+ unsigned long flags;
+ unsigned int ctrl;
+
+ local_irq_save(flags);
+
+ /*
+ * The Region Flush operation is specified by CTRL.RGN_OP[11..9]
+ * - b'000 (default) is Flush,
+ * - b'001 is Invalidate if CTRL.IM == 0
+ * - b'001 is Flush-n-Invalidate if CTRL.IM == 1
+ */
+ ctrl = read_aux_reg(ARC_REG_SLC_CTRL);
+
+ /* Don't rely on default value of IM bit */
+ if (!(op & OP_FLUSH)) /* i.e. OP_INV */
+ ctrl &= ~SLC_CTRL_IM; /* clear IM: Disable flush before Inv */
+ else
+ ctrl |= SLC_CTRL_IM;
+
+ if (op & OP_INV)
+ ctrl |= SLC_CTRL_RGN_OP_INV; /* Inv or flush-n-inv */
+ else
+ ctrl &= ~SLC_CTRL_RGN_OP_INV;
+
+ write_aux_reg(ARC_REG_SLC_CTRL, ctrl);
+
+ /*
+ * Lower bits are ignored, no need to clip
+ * END needs to be setup before START (latter triggers the operation)
+ * END can't be same as START, so add (l2_line_sz - 1) to sz
+ */
+ write_aux_reg(ARC_REG_SLC_RGN_END, (paddr + sz + l2_line_sz - 1));
+ write_aux_reg(ARC_REG_SLC_RGN_START, paddr);
+
+ while (read_aux_reg(ARC_REG_SLC_CTRL) & SLC_CTRL_BUSY);
+
+ local_irq_restore(flags);
+#endif
+}
+
+static inline int need_slc_flush(void)
+{
+ return is_isa_arcv2() && l2_line_sz;
+}
/***********************************************************
* Exported APIs
@@ -509,22 +561,30 @@ void flush_dcache_page(struct page *page)
}
EXPORT_SYMBOL(flush_dcache_page);
-
void dma_cache_wback_inv(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_FLUSH_N_INV);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_FLUSH_N_INV);
}
EXPORT_SYMBOL(dma_cache_wback_inv);
void dma_cache_inv(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_INV);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_INV);
}
EXPORT_SYMBOL(dma_cache_inv);
void dma_cache_wback(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_FLUSH);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_FLUSH);
}
EXPORT_SYMBOL(dma_cache_wback);
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 2cfe81dca92a..74a637a1cfc4 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -66,6 +66,18 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
/* This is bus address, platform dependent */
*dma_handle = (dma_addr_t)paddr;
+ /*
+ * Evict any existing L1 and/or L2 lines for the backing page
+ * in case it was used earlier as a normal "cached" page.
+ * Yeah this bit us - STAR 9000898266
+ *
+ * Although core does call flush_cache_vmap(), it gets kvaddr hence
+ * can't be used to efficiently flush L1 and/or L2 which need paddr
+ * Currently flush_cache_vmap nukes the L1 cache completely which
+ * will be optimized as a separate commit
+ */
+ dma_cache_wback_inv((unsigned long)paddr, size);
+
return kvaddr;
}
EXPORT_SYMBOL(dma_alloc_coherent);
--
1.9.1
WARNING: multiple messages have this Message-ID (diff)
From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: arnd@arndb.de, arc-linux-dev@synopsys.com,
Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: [PATCH 23/28] ARCv2: SLC: Handle explcit flush for DMA ops (w/o IO-coherency)
Date: Tue, 9 Jun 2015 17:18:23 +0530 [thread overview]
Message-ID: <1433850508-26317-24-git-send-email-vgupta@synopsys.com> (raw)
In-Reply-To: <1433850508-26317-1-git-send-email-vgupta@synopsys.com>
L2 cache on ARCHS processors is called SLC (System Level Cache)
For working DMA (in absence of hardware assisted IO Coherency) we need
to manage SLC explicitly when buffers transition between cpu and
controllers.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/include/asm/cache.h | 11 ++++++++
arch/arc/mm/cache.c | 64 ++++++++++++++++++++++++++++++++++++++++++--
arch/arc/mm/dma.c | 12 +++++++++
3 files changed, 85 insertions(+), 2 deletions(-)
diff --git a/arch/arc/include/asm/cache.h b/arch/arc/include/asm/cache.h
index d21c76d6b054..d67345d3e2d4 100644
--- a/arch/arc/include/asm/cache.h
+++ b/arch/arc/include/asm/cache.h
@@ -82,5 +82,16 @@ extern void read_decode_cache_bcr(void);
/*System-level cache (L2 cache) related Auxiliary registers */
#define ARC_REG_SLC_CFG 0x901
+#define ARC_REG_SLC_CTRL 0x903
+#define ARC_REG_SLC_FLUSH 0x904
+#define ARC_REG_SLC_INVALIDATE 0x905
+#define ARC_REG_SLC_RGN_START 0x914
+#define ARC_REG_SLC_RGN_END 0x916
+
+/* Bit val in SLC_CONTROL */
+#define SLC_CTRL_IM 0x040
+#define SLC_CTRL_DISABLE 0x001
+#define SLC_CTRL_BUSY 0x100
+#define SLC_CTRL_RGN_OP_INV 0x200
#endif /* _ASM_CACHE_H */
diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 0eaaee60fd0b..b29d62ed4f7e 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -21,6 +21,8 @@
#include <asm/cachectl.h>
#include <asm/setup.h>
+static int l2_line_sz;
+
void (*_cache_line_loop_ic_fn)(unsigned long paddr, unsigned long vaddr,
unsigned long sz, const int cacheop);
@@ -120,13 +122,16 @@ dc_chk:
p_dc->ver = dbcr.ver;
slc_chk:
+ if (!is_isa_arcv2())
+ return;
+
p_slc = &cpuinfo_arc700[cpu].slc;
READ_BCR(ARC_REG_SLC_BCR, sbcr);
if (sbcr.ver) {
READ_BCR(ARC_REG_SLC_CFG, slc_cfg);
p_slc->ver = sbcr.ver;
p_slc->sz_k = 128 << slc_cfg.sz;
- p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
+ l2_line_sz = p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
}
}
@@ -460,6 +465,53 @@ static void __ic_line_inv_vaddr(unsigned long paddr, unsigned long vaddr,
#endif /* CONFIG_ARC_HAS_ICACHE */
+noinline void slc_op(unsigned long paddr, unsigned long sz, const int op)
+{
+#ifdef CONFIG_ISA_ARCV2
+ unsigned long flags;
+ unsigned int ctrl;
+
+ local_irq_save(flags);
+
+ /*
+ * The Region Flush operation is specified by CTRL.RGN_OP[11..9]
+ * - b'000 (default) is Flush,
+ * - b'001 is Invalidate if CTRL.IM == 0
+ * - b'001 is Flush-n-Invalidate if CTRL.IM == 1
+ */
+ ctrl = read_aux_reg(ARC_REG_SLC_CTRL);
+
+ /* Don't rely on default value of IM bit */
+ if (!(op & OP_FLUSH)) /* i.e. OP_INV */
+ ctrl &= ~SLC_CTRL_IM; /* clear IM: Disable flush before Inv */
+ else
+ ctrl |= SLC_CTRL_IM;
+
+ if (op & OP_INV)
+ ctrl |= SLC_CTRL_RGN_OP_INV; /* Inv or flush-n-inv */
+ else
+ ctrl &= ~SLC_CTRL_RGN_OP_INV;
+
+ write_aux_reg(ARC_REG_SLC_CTRL, ctrl);
+
+ /*
+ * Lower bits are ignored, no need to clip
+ * END needs to be setup before START (latter triggers the operation)
+ * END can't be same as START, so add (l2_line_sz - 1) to sz
+ */
+ write_aux_reg(ARC_REG_SLC_RGN_END, (paddr + sz + l2_line_sz - 1));
+ write_aux_reg(ARC_REG_SLC_RGN_START, paddr);
+
+ while (read_aux_reg(ARC_REG_SLC_CTRL) & SLC_CTRL_BUSY);
+
+ local_irq_restore(flags);
+#endif
+}
+
+static inline int need_slc_flush(void)
+{
+ return is_isa_arcv2() && l2_line_sz;
+}
/***********************************************************
* Exported APIs
@@ -509,22 +561,30 @@ void flush_dcache_page(struct page *page)
}
EXPORT_SYMBOL(flush_dcache_page);
-
void dma_cache_wback_inv(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_FLUSH_N_INV);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_FLUSH_N_INV);
}
EXPORT_SYMBOL(dma_cache_wback_inv);
void dma_cache_inv(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_INV);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_INV);
}
EXPORT_SYMBOL(dma_cache_inv);
void dma_cache_wback(unsigned long start, unsigned long sz)
{
__dc_line_op_k(start, sz, OP_FLUSH);
+
+ if (need_slc_flush())
+ slc_op(start, sz, OP_FLUSH);
}
EXPORT_SYMBOL(dma_cache_wback);
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 2cfe81dca92a..74a637a1cfc4 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -66,6 +66,18 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
/* This is bus address, platform dependent */
*dma_handle = (dma_addr_t)paddr;
+ /*
+ * Evict any existing L1 and/or L2 lines for the backing page
+ * in case it was used earlier as a normal "cached" page.
+ * Yeah this bit us - STAR 9000898266
+ *
+ * Although core does call flush_cache_vmap(), it gets kvaddr hence
+ * can't be used to efficiently flush L1 and/or L2 which need paddr
+ * Currently flush_cache_vmap nukes the L1 cache completely which
+ * will be optimized as a separate commit
+ */
+ dma_cache_wback_inv((unsigned long)paddr, size);
+
return kvaddr;
}
EXPORT_SYMBOL(dma_alloc_coherent);
--
1.9.1
next prev parent reply other threads:[~2015-06-09 11:51 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 11:48 [PATCH 00/28] ARCv2 port to Linux - (B) ISA / Core / platform support Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 01/28] ARCv2: [intc] HS38 core interrupt controller Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 02/28] ARCv2: Support for ARCv2 ISA and HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 03/28] ARCv2: STAR 9000793984: Handle return from intr to Delay Slot Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 04/28] ARCv2: STAR 9000808988: signals involving " Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 05/28] ARCv2: STAR 9000814690: Really Re-enable interrupts to avoid deadlocks Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 06/28] ARCv2: MMUv4: TLB programming Model changes Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 07/28] ARCv2: MMUv4: cache programming model changes Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 08/28] ARCv2: MMUv4: support aliasing icache config Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 09/28] ARCv2: optimised string/mem lib routines Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 10/28] ARCv2: Adhere to Zero Delay loop restriction Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 11/28] ARCv2: extable: Enable sorting at build time Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-24 5:51 ` Vineet Gupta
2015-06-24 5:51 ` Vineet Gupta
2015-06-29 20:38 ` David Daney
2015-06-30 4:41 ` Vineet Gupta
2015-06-30 4:41 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 12/28] ARCv2: clocksource: Introduce 64bit local RTC counter Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 13/28] ARC: make plat_smp_ops weak to allow over-rides Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 14/28] ARCv2: SMP: ARConnect debug/robustness Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 15/28] ARCv2: SMP: clocksource: Enable Global Real Time counter Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 16/28] ARCv2: SMP: intc: IDU 2nd level intc for dynamic IRQ distribution Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 17/28] ARC: add compiler barrier to LLSC based cmpxchg Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:23 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 18/28] ARC: add smp barriers around atomics per memory-barrriers.txt Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:30 ` Peter Zijlstra
2015-06-10 9:17 ` Vineet Gupta
2015-06-10 10:53 ` Peter Zijlstra
2015-06-11 13:03 ` Vineet Gupta
2015-06-12 12:15 ` [PATCH v2] ARC: add smp barriers around atomics per Documentation/atomic_ops.txt Vineet Gupta
2015-06-12 12:15 ` Vineet Gupta
2015-06-12 13:04 ` Peter Zijlstra
2015-06-12 13:16 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 19/28] arch: conditionally define smp_{mb,rmb,wmb} Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:32 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 20/28] ARCv2: barriers Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:40 ` Peter Zijlstra
2015-06-10 9:34 ` Vineet Gupta
2015-06-10 10:58 ` Peter Zijlstra
2015-06-10 13:01 ` Will Deacon
2015-06-11 12:13 ` Vineet Gupta
2015-06-11 13:39 ` Will Deacon
2015-06-19 13:13 ` Vineet Gupta
2015-06-19 13:13 ` Vineet Gupta
2015-06-19 13:13 ` Vineet Gupta
2015-06-22 13:36 ` Will Deacon
2015-06-22 13:36 ` Will Deacon
2015-06-22 13:36 ` Will Deacon
2015-06-23 7:58 ` [PATCH v2 " Vineet Gupta
2015-06-23 7:58 ` Vineet Gupta
2015-06-23 8:49 ` Will Deacon
2015-06-23 9:03 ` Vineet Gupta
2015-06-23 9:26 ` Will Deacon
2015-06-23 9:52 ` [PATCH v3 22/28] " Vineet Gupta
2015-06-23 9:52 ` Vineet Gupta
2015-06-23 16:28 ` Will Deacon
2015-06-23 9:25 ` [PATCH v2 20/28] " Peter Zijlstra
2015-06-23 8:02 ` [PATCH " Vineet Gupta
2015-06-09 11:48 ` [PATCH 21/28] ARC: Reduce bitops lines of code using macros Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-12 12:20 ` [PATCH v2] " Vineet Gupta
2015-06-12 12:20 ` Vineet Gupta
2015-06-12 13:05 ` Peter Zijlstra
2015-06-09 11:48 ` [PATCH 22/28] ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 12:35 ` Peter Zijlstra
2015-06-10 10:01 ` Vineet Gupta
2015-06-10 11:02 ` Peter Zijlstra
2015-06-19 9:55 ` [PATCH v2 " Vineet Gupta
2015-06-19 9:55 ` Vineet Gupta
2015-06-19 9:59 ` Will Deacon
2015-06-19 10:09 ` Vineet Gupta
2015-06-23 7:59 ` Vineet Gupta
2015-06-23 7:59 ` Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta [this message]
2015-06-09 11:48 ` [PATCH 23/28] ARCv2: SLC: Handle explcit flush for DMA ops (w/o IO-coherency) Vineet Gupta
2015-06-09 11:48 ` [PATCH 24/28] ARCv2: All bits in place, allow ARCv2 builds Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 25/28] ARCv2: [nsim*hs*] Support simulation platforms for HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 26/28] ARC: [axs101] Prepare for AXS103 Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 27/28] ARCv2: [axs103] Support ARC SDP FPGA platform for HS38x cores Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
2015-06-09 11:48 ` [PATCH 28/28] ARCv2: [vdk] dts files and defconfig for HS38 VDK Vineet Gupta
2015-06-09 11:48 ` Vineet Gupta
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1433850508-26317-24-git-send-email-vgupta@synopsys.com \
--to=vineet.gupta1@synopsys.com \
--cc=arc-linux-dev@synopsys.com \
--cc=arnd@arndb.de \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.