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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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8e6d3fe1af
The inline assembly differences for v6 vs. v7 in the hvc_dcc driver are purely optimizations. On a v7 processor, an mrc with the pc sets the condition codes to the 28-31 bits of the register being read. It just so happens that the TX/RX full bits the DCC driver is testing for are high enough in the register to be put into the condition codes. On a v6 processor, this "feature" isn't implemented and thus we have to do the usual read, mask, test operations to check for TX/RX full. Since we already test the RX/TX full bits before calling __dcc_getchar() and __dcc_putchar() we don't actually need to do anything special for v7 over v6. The only difference is in hvc_dcc_get_chars(). We would test RX full, poll RX full, and then read a character from the buffer, whereas now we will test RX full, read a character from the buffer, and then test RX full again for the second iteration of the loop. It doesn't seem possible for the buffer to go from full to empty between testing the RX full and reading a character. Therefore, replace the v7 versions with the v6 versions and everything works the same. Acked-by: Tony Lindgren <tony@atomide.com> Cc: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Daniel Walker <dwalker@codeaurora.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
105 lines
2.3 KiB
C
105 lines
2.3 KiB
C
/* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*/
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#include <linux/console.h>
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#include <linux/delay.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/moduleparam.h>
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#include <linux/types.h>
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#include <asm/processor.h>
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#include "hvc_console.h"
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/* DCC Status Bits */
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#define DCC_STATUS_RX (1 << 30)
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#define DCC_STATUS_TX (1 << 29)
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static inline u32 __dcc_getstatus(void)
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{
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u32 __ret;
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asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg"
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: "=r" (__ret) : : "cc");
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return __ret;
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}
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static inline char __dcc_getchar(void)
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{
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char __c;
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asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg"
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: "=r" (__c));
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return __c;
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}
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static inline void __dcc_putchar(char c)
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{
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asm volatile("mcr p14, 0, %0, c0, c5, 0 @ write a char"
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: /* no output register */
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: "r" (c));
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}
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static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
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{
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int i;
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for (i = 0; i < count; i++) {
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while (__dcc_getstatus() & DCC_STATUS_TX)
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cpu_relax();
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__dcc_putchar(buf[i]);
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}
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return count;
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}
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static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
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{
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int i;
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for (i = 0; i < count; ++i)
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if (__dcc_getstatus() & DCC_STATUS_RX)
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buf[i] = __dcc_getchar();
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else
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break;
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return i;
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}
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static const struct hv_ops hvc_dcc_get_put_ops = {
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.get_chars = hvc_dcc_get_chars,
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.put_chars = hvc_dcc_put_chars,
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};
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static int __init hvc_dcc_console_init(void)
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{
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hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
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return 0;
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}
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console_initcall(hvc_dcc_console_init);
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static int __init hvc_dcc_init(void)
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{
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hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
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return 0;
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}
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device_initcall(hvc_dcc_init);
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