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References: <20230324072958.2993946-1-hsinyi@chromium.org> <f4573a49-ae05-07bf-4e7c-70037b4596b9@intel.com>
In-Reply-To: <f4573a49-ae05-07bf-4e7c-70037b4596b9@intel.com>
From:   Hsin-Yi Wang <hsinyi@chromium.org>
Date:   Fri, 24 Mar 2023 23:34:51 +0800
Message-ID: <CAJMQK-gzFc41kDxYHJQzuXtvaJnYN8zvsfHbam4TX+PaYoRE-w@mail.gmail.com>
Subject: Re: [PATCH] drm/bridge: it6505: Add lock for it6505 i2c bank
To:     Andrzej Hajda <andrzej.hajda@intel.com>
Cc:     Robert Foss <rfoss@kernel.org>,
        Douglas Anderson <dianders@chromium.org>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        kenneth.hung@ite.corp-partner.google.com,
        xiazhengqiao <xiazhengqiao@huaqin.corp-partner.google.com>
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On Fri, Mar 24, 2023 at 8:18=E2=80=AFPM Andrzej Hajda <andrzej.hajda@intel.=
com> wrote:
>
>
>
> On 24.03.2023 08:29, Hsin-Yi Wang wrote:
> > From: xiazhengqiao <xiazhengqiao@huaqin.corp-partner.google.com>
> >
> > When the i2c bank register (REG_BANK_SEL) is set to 1,
> > only the registers belong to bank 1 can be written.
> > There will be a race condition when a process is writing
> > bank 0 registers while another process set the bank to 1.
> > Add a mutex to handle regmap read/write locking for
> > registers in multiple i2c bank. Since the driver now
> > owns the lock, there's no need to use regmap API's lock.
> >
> > Signed-off-by: xiazhengqiao <xiazhengqiao@huaqin.corp-partner.google.co=
m>
> > Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> > ---
> >   drivers/gpu/drm/bridge/ite-it6505.c | 72 ++++++++++++++++++++++------=
-
> >   1 file changed, 55 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/brid=
ge/ite-it6505.c
> > index bc451b2a77c28..1a8dcc49fc1ee 100644
> > --- a/drivers/gpu/drm/bridge/ite-it6505.c
> > +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> > @@ -258,12 +258,12 @@
> >   #define REG_AUD_INFOFRAM_SUM 0xFB
> >
> >   /* the following six registers are in bank1 */
> > -#define REG_DRV_0_DB_800_MV 0x7E
> > -#define REG_PRE_0_DB_800_MV 0x7F
> > -#define REG_PRE_3P5_DB_800_MV 0x81
> > -#define REG_SSC_CTRL0 0x88
> > -#define REG_SSC_CTRL1 0x89
> > -#define REG_SSC_CTRL2 0x8A
> > +#define REG_DRV_0_DB_800_MV 0x17E
> > +#define REG_PRE_0_DB_800_MV 0x17F
> > +#define REG_PRE_3P5_DB_800_MV 0x181
> > +#define REG_SSC_CTRL0 0x188
> > +#define REG_SSC_CTRL1 0x189
> > +#define REG_SSC_CTRL2 0x18A
> >
> >   #define RBR DP_LINK_BW_1_62
> >   #define HBR DP_LINK_BW_2_7
> > @@ -414,12 +414,14 @@ struct it6505 {
> >       struct mutex extcon_lock;
> >       struct mutex mode_lock; /* used to bridge_detect */
> >       struct mutex aux_lock; /* used to aux data transfers */
> > +     struct mutex bank_lock; /* used to protect i2c bank access */
> >       struct regmap *regmap;
> >       struct drm_display_mode source_output_mode;
> >       struct drm_display_mode video_info;
> >       struct notifier_block event_nb;
> >       struct extcon_dev *extcon;
> >       struct work_struct extcon_wq;
> > +     int bank_state;   /* 1 indicates bank 1, 0 indicates bank 0 */
> >       int extcon_state;
> >       enum drm_connector_status connector_status;
> >       enum link_train_status link_state;
> > @@ -502,8 +504,22 @@ static const struct regmap_config it6505_regmap_co=
nfig =3D {
> >       .val_bits =3D 8,
> >       .volatile_table =3D &it6505_bridge_volatile_table,
> >       .cache_type =3D REGCACHE_NONE,
> > +     .disable_locking =3D true,
> > +     .can_sleep =3D true,
> >   };
> >
> > +static int it6505_config_bank(struct it6505 *it6505, unsigned int reg_=
addr)
> > +{
> > +     int err =3D 0, target =3D !!(reg_addr > 0xff);
> > +
> > +     if (target !=3D it6505->bank_state) {
>
> It would be better to return if equal, this way you can avoid indentation=
.
>
Will fix in v2.
> > +             err =3D regmap_write(it6505->regmap, REG_BANK_SEL, target=
);
> > +             if (!err)
> > +                     it6505->bank_state =3D target;
> > +     }
> > +     return err;
> > +}
> > +
> >   static int it6505_read(struct it6505 *it6505, unsigned int reg_addr)
> >   {
> >       unsigned int value;
> > @@ -513,7 +529,10 @@ static int it6505_read(struct it6505 *it6505, unsi=
gned int reg_addr)
> >       if (!it6505->powered)
> >               return -ENODEV;
> >
> > -     err =3D regmap_read(it6505->regmap, reg_addr, &value);
> > +     mutex_lock(&it6505->bank_lock);
> > +     err =3D it6505_config_bank(it6505, reg_addr);
> > +     err |=3D regmap_read(it6505->regmap, reg_addr & 0xff, &value);
>
> Shoudn't be rather if (!err) err =3D regmap_read(...) ?
>
Will fix in v2.
> > +     mutex_unlock(&it6505->bank_lock);
> >       if (err < 0) {
> >               dev_err(dev, "read failed reg[0x%x] err: %d", reg_addr, e=
rr);
> >               return err;
> > @@ -531,8 +550,10 @@ static int it6505_write(struct it6505 *it6505, uns=
igned int reg_addr,
> >       if (!it6505->powered)
> >               return -ENODEV;
> >
> > -     err =3D regmap_write(it6505->regmap, reg_addr, reg_val);
> > -
> > +     mutex_lock(&it6505->bank_lock);
> > +     err =3D it6505_config_bank(it6505, reg_addr);
> > +     err |=3D regmap_write(it6505->regmap, reg_addr & 0xff, reg_val);
> > +     mutex_unlock(&it6505->bank_lock);
> >       if (err < 0) {
> >               dev_err(dev, "write failed reg[0x%x] =3D 0x%x err =3D %d"=
,
> >                       reg_addr, reg_val, err);
> > @@ -551,7 +572,10 @@ static int it6505_set_bits(struct it6505 *it6505, =
unsigned int reg,
> >       if (!it6505->powered)
> >               return -ENODEV;
> >
> > -     err =3D regmap_update_bits(it6505->regmap, reg, mask, value);
> > +     mutex_lock(&it6505->bank_lock);
> > +     err =3D it6505_config_bank(it6505, reg);
> > +     err |=3D regmap_update_bits(it6505->regmap, reg & 0xff, mask, val=
ue);
> > +     mutex_unlock(&it6505->bank_lock);
> >       if (err < 0) {
> >               dev_err(dev, "write reg[0x%x] =3D 0x%x mask =3D 0x%x fail=
ed err %d",
> >                       reg, value, mask, err);
> > @@ -892,7 +916,10 @@ static void it6505_aux_reset(struct it6505 *it6505=
)
> >
> >   static void it6505_reset_logic(struct it6505 *it6505)
> >   {
> > +     mutex_lock(&it6505->bank_lock);
> > +     it6505_config_bank(it6505, REG_RESET_CTRL);
> >       regmap_write(it6505->regmap, REG_RESET_CTRL, ALL_LOGIC_RESET);
> > +     mutex_unlock(&it6505->bank_lock);
>
> Why not call it6505_write ?
Will fix in v2.
> >       usleep_range(1000, 1500);
> >   }
> >
> > @@ -972,9 +999,14 @@ static ssize_t it6505_aux_operation(struct it6505 =
*it6505,
> >       it6505_write(it6505, REG_AUX_ADR_16_19,
> >                    ((address >> 16) & 0x0F) | ((size - 1) << 4));
> >
> > -     if (cmd =3D=3D CMD_AUX_NATIVE_WRITE)
> > +     if (cmd =3D=3D CMD_AUX_NATIVE_WRITE) {
> > +             mutex_lock(&it6505->bank_lock);
> > +             it6505_config_bank(it6505, REG_AUX_OUT_DATA0);
> >               regmap_bulk_write(it6505->regmap, REG_AUX_OUT_DATA0, buff=
er,
> >                                 size);
> > +             mutex_unlock(&it6505->bank_lock);
> > +     }
> > +
> >
> >       /* Aux Fire */
> >       it6505_write(it6505, REG_AUX_CMD_REQ, cmd);
> > @@ -1197,9 +1229,12 @@ static int it6505_send_video_infoframe(struct it=
6505 *it6505,
> >       if (err)
> >               return err;
> >
> > -     err =3D regmap_bulk_write(it6505->regmap, REG_AVI_INFO_DB1,
> > +     mutex_lock(&it6505->bank_lock);
> > +     err =3D it6505_config_bank(it6505, REG_AVI_INFO_DB1);
> > +     err |=3D regmap_bulk_write(it6505->regmap, REG_AVI_INFO_DB1,
> >                               buffer + HDMI_INFOFRAME_HEADER_SIZE,
> >                               frame->length);
> > +     mutex_unlock(&it6505->bank_lock);
>
> Common code with it6505_aux_operation, maybe it6505_bulk_write ?
Will fix in v2.
>
> Have you checked if regmap does not support banking? IMO it should be
> implemented there.

Thanks for the suggestion. Do you mean regmap_field*? I think the
banking in that series of API is different to the use case here. Since
we would need to additionally set REG_BANK_SEL to 0 or 1, we still
need a similar approach to this patch.
We can also use regmap_multi_reg_write() to carry REG_BANK_SEL and the
reg we want to write but that would have set REG_BANK_SEL multiple
times unnecessarily (eg. a consequent write on 2 regs on bank 0
doesn't need to write REG_BANK_SEL to 0 again on the second one.)


>
> Regards
> Andrzej
>
> >       if (err)
> >               return err;
> >
> > @@ -1267,7 +1302,6 @@ static void it6505_init(struct it6505 *it6505)
> >       it6505_write(it6505, REG_TIME_STMP_CTRL,
> >                    EN_SSC_GAT | EN_ENHANCE_VID_STMP | EN_ENHANCE_AUD_ST=
MP);
> >       it6505_write(it6505, REG_INFOFRAME_CTRL, 0x00);
> > -     it6505_write(it6505, REG_BANK_SEL, 0x01);
> >       it6505_write(it6505, REG_DRV_0_DB_800_MV,
> >                    afe_setting_table[it6505->afe_setting][0]);
> >       it6505_write(it6505, REG_PRE_0_DB_800_MV,
> > @@ -1277,7 +1311,6 @@ static void it6505_init(struct it6505 *it6505)
> >       it6505_write(it6505, REG_SSC_CTRL0, 0x9E);
> >       it6505_write(it6505, REG_SSC_CTRL1, 0x1C);
> >       it6505_write(it6505, REG_SSC_CTRL2, 0x42);
> > -     it6505_write(it6505, REG_BANK_SEL, 0x00);
> >   }
> >
> >   static void it6505_video_disable(struct it6505 *it6505)
> > @@ -1506,11 +1539,9 @@ static void it6505_setup_ssc(struct it6505 *it65=
05)
> >       it6505_set_bits(it6505, REG_TRAIN_CTRL0, SPREAD_AMP_5,
> >                       it6505->enable_ssc ? SPREAD_AMP_5 : 0x00);
> >       if (it6505->enable_ssc) {
> > -             it6505_write(it6505, REG_BANK_SEL, 0x01);
> >               it6505_write(it6505, REG_SSC_CTRL0, 0x9E);
> >               it6505_write(it6505, REG_SSC_CTRL1, 0x1C);
> >               it6505_write(it6505, REG_SSC_CTRL2, 0x42);
> > -             it6505_write(it6505, REG_BANK_SEL, 0x00);
> >               it6505_write(it6505, REG_SP_CTRL0, 0x07);
> >               it6505_write(it6505, REG_IP_CTRL1, 0x29);
> >               it6505_write(it6505, REG_IP_CTRL2, 0x03);
> > @@ -1983,8 +2014,11 @@ static int it6505_setup_sha1_input(struct it6505=
 *it6505, u8 *sha1_input)
> >       it6505_set_bits(it6505, REG_HDCP_CTRL2, HDCP_EN_M0_READ,
> >                       HDCP_EN_M0_READ);
> >
> > -     err =3D regmap_bulk_read(it6505->regmap, REG_M0_0_7,
> > +     mutex_lock(&it6505->bank_lock);
> > +     err =3D it6505_config_bank(it6505, REG_M0_0_7);
> > +     err |=3D regmap_bulk_read(it6505->regmap, REG_M0_0_7,
> >                              sha1_input + msg_count, 8);
> > +     mutex_unlock(&it6505->bank_lock);
> >
> >       it6505_set_bits(it6505, REG_HDCP_CTRL2, HDCP_EN_M0_READ, 0x00);
> >
> > @@ -2577,6 +2611,9 @@ static int it6505_poweron(struct it6505 *it6505)
> >       }
> >
> >       it6505->powered =3D true;
> > +     mutex_lock(&it6505->bank_lock);
> > +     it6505->bank_state =3D 0;
> > +     mutex_unlock(&it6505->bank_lock);
> >       it6505_reset_logic(it6505);
> >       it6505_int_mask_enable(it6505);
> >       it6505_init(it6505);
> > @@ -3359,6 +3396,7 @@ static int it6505_i2c_probe(struct i2c_client *cl=
ient)
> >       mutex_init(&it6505->extcon_lock);
> >       mutex_init(&it6505->mode_lock);
> >       mutex_init(&it6505->aux_lock);
> > +     mutex_init(&it6505->bank_lock);
> >
> >       it6505->bridge.of_node =3D client->dev.of_node;
> >       it6505->connector_status =3D connector_status_disconnected;
>