On Wed, Mar 10, 2010 at 4:44 AM, Jean Delvare <khali@xxxxxxxxxxxx> wrote:
> Hi Alex,
>
> Sorry for the late answer.
>
> On Mon, 11 Jan 2010 17:13:50 -0500, Alex Deucher wrote:
>> Hi,
>>
>> I'm adding support for the i2c controllers on radeon hardware and
>> I have a few questions. I have a radeon-algo that encapsulates all
>> the various hw i2c controller functionality, however, it uses a
>> bit-algo bus internally for cases where you have to use bit-banging
>> rather than the hardware i2c engines. Also, for bit banging to work
>> properly, you need to do some things before the bit-algo transaction
>> (basically masking the gpios for software use).
>
> There used to be a patch floating around that added pre- and post-xfer
> hooks to i2c-algo-bit... I couldn't find it again, so I rewrote it:
>
> From: Jean Delvare <khali@xxxxxxxxxxxx>
> Subject: i2c-algo-bit: Add pre- and post-xfer hooks
>
> Drivers might have to do random things before and/or after I2C
> transfers. Add hooks to the i2c-algo-bit implementation to let them do
> so.
>
> Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
> ---
> drivers/i2c/algos/i2c-algo-bit.c | 9 +++++++++
> include/linux/i2c-algo-bit.h | 2 ++
> 2 files changed, 11 insertions(+)
>
> --- linux-2.6.34-rc1.orig/drivers/i2c/algos/i2c-algo-bit.c 2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.34-rc1/drivers/i2c/algos/i2c-algo-bit.c 2010-03-09 18:52:50.000000000 +0100
> @@ -522,6 +522,12 @@ static int bit_xfer(struct i2c_adapter *
> int i, ret;
> unsigned short nak_ok;
>
> + if (adap->pre_xfer) {
> + ret = adap->pre_xfer(i2c_adap, adap->data);
> + if (ret < 0)
> + return ret;
> + }
> +
> bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
> i2c_start(adap);
> for (i = 0; i < num; i++) {
> @@ -570,6 +576,9 @@ static int bit_xfer(struct i2c_adapter *
> bailout:
> bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
> i2c_stop(adap);
> +
> + if (adap->post_xfer)
> + adap->post_xfer(i2c_adap, adap->data);
> return ret;
> }
>
> --- linux-2.6.34-rc1.orig/include/linux/i2c-algo-bit.h 2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.34-rc1/include/linux/i2c-algo-bit.h 2010-03-09 18:53:06.000000000 +0100
> @@ -32,6 +32,8 @@
> */
> struct i2c_algo_bit_data {
> void *data; /* private data for lowlevel routines */
> + int (*pre_xfer) (struct i2c_adapter *i2c_adap, void *data);
> + void (*post_xfer) (struct i2c_adapter *i2c_adap, void *data);
> void (*setsda) (void *data, int state);
> void (*setscl) (void *data, int state);
> int (*getsda) (void *data);
>
> Would it help?
>
>> Right now we use
>> bit-algo i2c for the ddc buses, but they won't work externally to the
>> driver without the proper gpio masking prior to using them. In the
>> radeon-algo patches, I use bit algo internally when I cannot use the
>> hardware i2c engines, or in cases where I haven't implemented support
>> yet for the hardware engine (as most gpios can be driven by sw or the
>> hw engine). The problem is, this exposes the i2c bit-algo buses as
>> well as the radeon-algo buses.
>
> This is bad, as it defeats the slave address uniqueness mechanism. Bad
> things could happen. Would the patch above be sufficient to solve your
> case?
>
>> Is there a way to not expose the bit-algo buses that are used
>> internally?
>
> No, this is not possible at the time being. That being said, it
> shouldn't be difficult, if the need exists. Looking at i2c-algo-bit,
> the registration part is split into a preparation step and the actual
> registration with i2c-core. The preparation step if done by
> i2c_bit_prepare_bus(). If we exported this function, then you could
> easily call it to create an internal i2c-algo-bit-based adapter, which
> you wouldn't have to register if you don't want to:
>
> From: Jean Delvare <khali@xxxxxxxxxxxx>
> Subject: i2c-algo-bit: Export i2c_bit_prepare_bus
>
> This lets drivers make use of the i2c-algo-bit implementation without
> actually registering the i2c adapter in question. This is useful to
> drivers which need more than the i2c-algo-bit driver offers.
>
> Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
> ---
> drivers/i2c/algos/i2c-algo-bit.c | 3 ++-
> include/linux/i2c-algo-bit.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> --- linux-2.6.34-rc1.orig/drivers/i2c/algos/i2c-algo-bit.c 2010-03-10 08:09:03.000000000 +0100
> +++ linux-2.6.34-rc1/drivers/i2c/algos/i2c-algo-bit.c 2010-03-10 10:23:51.000000000 +0100
> @@ -601,7 +601,7 @@ static const struct i2c_algorithm i2c_bi
> /*
> * registering functions to load algorithms at runtime
> */
> -static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
> +int i2c_bit_prepare_bus(struct i2c_adapter *adap)
> {
> struct i2c_algo_bit_data *bit_adap = adap->algo_data;
>
> @@ -617,6 +617,7 @@ static int i2c_bit_prepare_bus(struct i2
>
> return 0;
> }
> +EXPORT_SYMBOL(i2c_bit_prepare_bus);
>
> int i2c_bit_add_bus(struct i2c_adapter *adap)
> {
> --- linux-2.6.34-rc1.orig/include/linux/i2c-algo-bit.h 2010-03-10 08:09:03.000000000 +0100
> +++ linux-2.6.34-rc1/include/linux/i2c-algo-bit.h 2010-03-10 10:24:03.000000000 +0100
> @@ -47,6 +47,7 @@ struct i2c_algo_bit_data {
> int timeout; /* in jiffies */
> };
>
> +int i2c_bit_prepare_bus(struct i2c_adapter *);
> int i2c_bit_add_bus(struct i2c_adapter *);
> int i2c_bit_add_numbered_bus(struct i2c_adapter *);
>
>
> With this possibility, I guess you wouldn't even need the first patch
> any longer? If both are needed, that's fine with me, but if only one is
> needed, that's even better.
>
>> I've attached the patches for reference.
>
> Please let me know if either or both of my 2 proposals above fit your
> needs.
I tested the second patch with a trivial patch to the radeon drm:
--- a/drivers/gpu/drm/radeon/radeon_i2c.c
+++ b/drivers/gpu/drm/radeon/radeon_i2c.c
@@ -892,9 +892,9 @@ struct radeon_i2c_chan *radeon_i2c_create(struct
drm_device *dev,
* make this, 2 jiffies is a lot more reliable */
i2c->algo.radeon.bit_data.timeout = 2;
i2c->algo.radeon.bit_data.data = i2c;
- ret = i2c_bit_add_bus(&i2c->algo.radeon.bit_adapter);
+ ret = i2c_bit_prepare_bus(&i2c->algo.radeon.bit_adapter);
if (ret) {
- DRM_ERROR("Failed to register internal bit i2c %s\n", name);
+ DRM_ERROR("Failed to prepare internal bit i2c %s\n", name);
goto out_free;
}
/* set the radeon i2c adapter */
However, just calling i2c_bit_prepare_bus does not appear to be
enough. as I get the following oops:
[ 1443.236030] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 1443.236125] IP: [<ffffffff8139913d>] __mutex_lock_slowpath+0xad/0x180
[ 1443.236192] PGD 677cd067 PUD 68d2c067 PMD 0
[ 1443.236306] Oops: 0002 [#1] SMP
[ 1443.236392] last sysfs file:
/sys/devices/platform/radeon_cp.0/firmware/radeon_cp.0/loading
[ 1443.236429] CPU 0
[ 1443.236486] Modules linked in: radeon(+) ttm drm_kms_helper drm
cfbcopyarea i2c_algo_bit i2c_core cfbimgblt cfbfillrect binfmt_misc
ipv6 powernow_k8 cpufreq_stats cpufreq_conservative cpufreq_userspace
cpufreq_ondemand freq_table cpufreq_powersave video output container
power_meter pci_slot fan sbs acpi_pad sbshc battery iptable_filter
ip_tables x_tables ac sbp2 fuse snd_hda_codec_atihdmi
snd_hda_codec_realtek snd_pcm_oss snd_hda_intel snd_hda_codec
snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss usbhid snd_seq_midi
hid snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device
amd64_edac_mod snd ehci_hcd ohci_hcd ohci1394 pata_acpi pcspkr
edac_core soundcore snd_page_alloc evdev ata_generic usbcore sg r8169
mii ieee1394 thermal button processor [last unloaded: cfbfillrect]
[ 1443.238565] Pid: 16998, comm: work_for_cpu Not tainted 2.6.32 #252
System Product Name
[ 1443.238602] RIP: 0010:[<ffffffff8139913d>] [<ffffffff8139913d>]
__mutex_lock_slowpath+0xad/0x180
[ 1443.238669] RSP: 0018:ffff880068e75b00 EFLAGS: 00010246
[ 1443.238702] RAX: ffff880068e75b10 RBX: ffff88006769ea24 RCX: 0000000000007e40
[ 1443.238736] RDX: 0000000000000000 RSI: ffff880068e75cd0 RDI: ffff88006769ea24
[ 1443.238770] RBP: ffff880068e75b60 R08: 0000000000000000 R09: 0000000000000400
[ 1443.238804] R10: 000000000000000a R11: 0000000000000000 R12: ffff88006769ea20
[ 1443.238837] R13: ffff88006769ea38 R14: ffff88006769ea28 R15: 0000000000000000
[ 1443.238871] FS: 00007f69514f36e0(0000) GS:ffff880001a00000(0000)
knlGS:0000000000000000
[ 1443.238908] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
[ 1443.238941] CR2: 0000000000000000 CR3: 000000006610f000 CR4: 00000000000006f0
[ 1443.238974] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1443.239008] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 1443.239043] Process work_for_cpu (pid: 16998, threadinfo
ffff880068e74000, task ffff880065f65b40)
[ 1443.239079] Stack:
[ 1443.239109] ffff880068e75fd8 ffff880065f65b40 ffff88006769ea28
ffffffff811fe7b8
[ 1443.239225] <0> 0000003000000020 ffff880068e75c00 ffff880068e75b40
ffff88006769ea20
[ 1443.239395] <0> 0000000000000002 00000000ffffffa1 ffff880068e75cd0
0000000000000002
[ 1443.239595] Call Trace:
[ 1443.239630] [<ffffffff811fe7b8>] ? sprintf+0x68/0x70
[ 1443.239665] [<ffffffff81399066>] mutex_lock+0x26/0x50
[ 1443.239701] [<ffffffffa0182638>] i2c_transfer+0xe8/0xf0 [i2c_core]
[ 1443.239763] [<ffffffffa04e94c5>] radeon_sw_i2c_xfer+0x45/0x70 [radeon]
[ 1443.239818] [<ffffffffa04e957e>] radeon_i2c_xfer+0x8e/0x16e0 [radeon]
[ 1443.239855] [<ffffffffa0182604>] i2c_transfer+0xb4/0xf0 [i2c_core]
[ 1443.239901] [<ffffffffa048d148>] drm_do_probe_ddc_edid+0x48/0x60 [drm]
[ 1443.239943] [<ffffffffa048e128>] drm_ddc_read_edid+0x38/0xb0 [drm]
[ 1443.239984] [<ffffffffa048e23a>] drm_get_edid+0x9a/0x180 [drm]
[ 1443.240006] [<ffffffffa04e6cd4>] radeon_modeset_init+0x494/0x7b0 [radeon]
[ 1443.240006] [<ffffffffa051b9c0>] ? r600_init+0x220/0x390 [radeon]
[ 1443.240006] [<ffffffffa04c625d>] radeon_driver_load_kms+0xdd/0x1b0 [radeon]
[ 1443.240006] [<ffffffffa048388a>] drm_get_dev+0x35a/0x500 [drm]
[ 1443.240006] [<ffffffff810748f0>] ? do_work_for_cpu+0x0/0x30
[ 1443.240006] [<ffffffffa053778e>] radeon_pci_probe+0x10/0x263 [radeon]
[ 1443.240006] [<ffffffff8120f4c2>] local_pci_probe+0x12/0x20
[ 1443.240006] [<ffffffff81074903>] do_work_for_cpu+0x13/0x30
[ 1443.240006] [<ffffffff810748f0>] ? do_work_for_cpu+0x0/0x30
[ 1443.240006] [<ffffffff810787ce>] kthread+0x8e/0xa0
[ 1443.240006] [<ffffffff81012faa>] child_rip+0xa/0x20
[ 1443.240006] [<ffffffff81078740>] ? kthread+0x0/0xa0
[ 1443.240006] [<ffffffff81012fa0>] ? child_rip+0x0/0x20
[ 1443.240006] Code: a8 83 78 20 63 7f b7 49 8d 5c 24 04 4d 8d 74 24
08 48 89 df e8 25 14 00 00 49 8b 54 24 10 48 8d 45 b0 4c 89 75 b0 49
89 44 24 10 <48> 89 02 48 8b 45 a8 48 89 55 b8 48 c7 c2 ff ff ff ff 48
89 45
[ 1443.241788] RIP [<ffffffff8139913d>] __mutex_lock_slowpath+0xad/0x180
[ 1443.241788] RSP <ffff880068e75b00>
[ 1443.241788] CR2: 0000000000000000
[ 1443.242594] ---[ end trace af8d6cef4b61feb3 ]---
Alex
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
