[PATCH v1 1/2] drm/i2c: tda998x: access chip registers via a regmap
Russell King - ARM Linux admin
linux at armlinux.org.uk
Fri Jun 21 22:06:20 UTC 2019
On Fri, Jun 21, 2019 at 05:13:33PM -0400, Sven Van Asbroeck wrote:
> On Fri, Jun 21, 2019 at 11:15 AM Russell King - ARM Linux admin
> <linux at armlinux.org.uk> wrote:
> >
> > Another con is the need to keep the functions that detail the register
> > properties up to date, which if they're wrong may result in unexpected
> > behaviour.
> >
> > I subscribe to the "keep it simple" approach, and regmap, although
> > useful, seems like a giant sledgehammer for this.
> >
>
> Thank you for the review !
>
> I added this back when I was debugging audio artifacts related to this
> chip. The regmap's debugfs binding was extremely useful. So I
> dressed it up a bit in the hope that it would have some general use.
>
> But if the cons outweigh the pros, then this is as far as this patch
> will go...
I won't disagree that debugfs access to the registers is useful,
especially as I keep this patch locally for that exact purpose:
8<===
From: Russell King <rmk+kernel at armlinux.org.uk>
Subject: [PATCH] drm/i2c: tda998x: debugfs register access
Add support for dumping the register contents via debugfs, with a
mechanism to write to the TDA998x registers to allow experimentation.
Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
---
drivers/gpu/drm/i2c/tda998x_drv.c | 114 ++++++++++++++++++++++++++++++++++++++
1 file changed, 114 insertions(+)
diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 5312fde8b624..6ad1fd1d28a5 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -16,10 +16,13 @@
*/
#include <linux/component.h>
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
#include <linux/gpio/consumer.h>
#include <linux/hdmi.h>
#include <linux/module.h>
#include <linux/platform_data/tda9950.h>
+#include <linux/seq_file.h>
#include <linux/irq.h>
#include <sound/asoundef.h>
#include <sound/hdmi-codec.h>
@@ -1239,6 +1242,116 @@ static int tda998x_audio_codec_init(struct tda998x_priv *priv,
}
/* DRM connector functions */
+static u8 tda998x_debugfs_pages[] = {
+ 0x00, 0x01, 0x02, 0x09, 0x10, 0x11, 0x12, 0x13
+};
+
+static void *tda998x_regs_start(struct seq_file *s, loff_t *pos)
+{
+ return *pos < ARRAY_SIZE(tda998x_debugfs_pages) ? pos : NULL;
+}
+
+static void *tda998x_regs_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ (*pos)++;
+ return *pos < ARRAY_SIZE(tda998x_debugfs_pages) ? pos : NULL;
+}
+
+static void tda998x_regs_stop(struct seq_file *s, void *v)
+{
+}
+
+static int tda998x_regs_show(struct seq_file *s, void *v)
+{
+ struct tda998x_priv *priv = s->private;
+ u8 page = tda998x_debugfs_pages[*(loff_t *)v];
+ unsigned int i, j;
+ u8 buf[16];
+
+ seq_printf(s, "==================== page %02x ======================\n", page);
+ seq_printf(s, " 0 1 2 3 4 5 6 7 8 9 a b c d e f\n");
+ for (i = 0; i < 256; i += sizeof(buf)) {
+ reg_read_range(priv, REG(page, i), buf, sizeof(buf));
+
+ seq_printf(s, "%02x:", i);
+ for (j = 0; j < sizeof(buf); j++)
+ seq_printf(s, " %02x", buf[j]);
+ seq_printf(s, " : ");
+ for (j = 0; j < sizeof(buf); j++)
+ seq_printf(s, "%c",
+ isascii(buf[j]) && isprint(buf[j]) ?
+ buf[j] : '.');
+ seq_putc(s, '\n');
+ }
+ return 0;
+}
+
+static const struct seq_operations tda998x_regs_sops = {
+ .start = tda998x_regs_start,
+ .next = tda998x_regs_next,
+ .stop = tda998x_regs_stop,
+ .show = tda998x_regs_show,
+};
+
+static int tda998x_regs_open(struct inode *inode, struct file *file)
+{
+ int ret = seq_open(file, &tda998x_regs_sops);
+ if (ret < 0)
+ return ret;
+
+ ((struct seq_file *)file->private_data)->private = inode->i_private;
+
+ return 0;
+}
+
+static ssize_t tda998x_regs_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *offset)
+{
+ struct tda998x_priv *priv =
+ ((struct seq_file *)file->private_data)->private;
+ unsigned int page, addr, mask, val;
+ unsigned char rval;
+ char buffer[16];
+
+ memset(buffer, 0, sizeof(buffer));
+ if (count > sizeof(buffer) - 1)
+ count = sizeof(buffer) - 1;
+ if (copy_from_user(buffer, buf, count))
+ return -EFAULT;
+
+ if (sscanf(buffer, "%x %x %x %x", &page, &addr, &mask, &val) != 4)
+ return -EINVAL;
+ if (page > 0xff || addr > 0xff || mask > 0xff || val > 0xff)
+ return -ERANGE;
+
+ rval = reg_read(priv, REG(page, addr));
+ rval &= ~mask;
+ rval |= val & mask;
+ reg_write(priv, REG(page, addr), rval);
+
+ printk("i2c write %02x @ page:%02x address:%02x\n", rval, page, addr);
+
+ return count;
+}
+
+static const struct file_operations tda998x_regs_fops = {
+ .owner = THIS_MODULE,
+ .open = tda998x_regs_open,
+ .read = seq_read,
+ .write = tda998x_regs_write,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static int tda998x_late_register(struct drm_connector *connector)
+{
+ struct tda998x_priv *priv = conn_to_tda998x_priv(connector);
+
+ debugfs_create_file("tda998x-regs", 0600, connector->debugfs_entry,
+ priv, &tda998x_regs_fops);
+
+ return 0;
+}
static enum drm_connector_status
tda998x_connector_detect(struct drm_connector *connector, bool force)
@@ -1259,6 +1372,7 @@ static const struct drm_connector_funcs tda998x_connector_funcs = {
.reset = drm_atomic_helper_connector_reset,
.fill_modes = drm_helper_probe_single_connector_modes,
.detect = tda998x_connector_detect,
+ .late_register = tda998x_late_register,
.destroy = tda998x_connector_destroy,
.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
--
2.7.4
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
More information about the dri-devel
mailing list