| Message ID | 20240403090246.1495487-1-jammy_huang@aspeedtech.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/ast: Fix soft lockup | expand |
Am 03.04.24 um 11:02 schrieb Jammy Huang: > There is a while-loop in ast_dp_set_on_off() that could lead to > infinite-loop. This is because the register, VGACRI-Dx, checked in > this API is a scratch register actually controlled by a MCU, named > DPMCU, in BMC. > > These scratch registers are protected by scu-lock. If suc-lock is not > off, DPMCU can not update these registers and then host will have soft > lockup due to never updated status. > > DPMCU is used to control DP and relative registers to handshake with > host's VGA driver. Even the most time-consuming task, DP's link > training, is less than 100ms. 200ms should be enough. > > Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> > Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > --- > drivers/gpu/drm/ast/ast_dp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c > index ebb6d8ebd44e..1e9259416980 100644 > --- a/drivers/gpu/drm/ast/ast_dp.c > +++ b/drivers/gpu/drm/ast/ast_dp.c > @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > { > struct ast_device *ast = to_ast_device(dev); > u8 video_on_off = on; > + u32 i = 0; > > // Video On/Off > ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on); > @@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) { > // wait 1 ms > mdelay(1); > + if (++i > 200) > + break; > } > } > } > > base-commit: b0546776ad3f332e215cebc0b063ba4351971cca
Hi, I've added a Fixes tag and pushed to patch into drm-misc-fixes. Best regards Thomas Am 03.04.24 um 11:02 schrieb Jammy Huang: > There is a while-loop in ast_dp_set_on_off() that could lead to > infinite-loop. This is because the register, VGACRI-Dx, checked in > this API is a scratch register actually controlled by a MCU, named > DPMCU, in BMC. > > These scratch registers are protected by scu-lock. If suc-lock is not > off, DPMCU can not update these registers and then host will have soft > lockup due to never updated status. > > DPMCU is used to control DP and relative registers to handshake with > host's VGA driver. Even the most time-consuming task, DP's link > training, is less than 100ms. 200ms should be enough. > > Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> > Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> > --- > drivers/gpu/drm/ast/ast_dp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c > index ebb6d8ebd44e..1e9259416980 100644 > --- a/drivers/gpu/drm/ast/ast_dp.c > +++ b/drivers/gpu/drm/ast/ast_dp.c > @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > { > struct ast_device *ast = to_ast_device(dev); > u8 video_on_off = on; > + u32 i = 0; > > // Video On/Off > ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on); > @@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) { > // wait 1 ms > mdelay(1); > + if (++i > 200) > + break; > } > } > } > > base-commit: b0546776ad3f332e215cebc0b063ba4351971cca
Hi Thomas, Thank you. Regards, Jammy Huang > > Hi, > > I've added a Fixes tag and pushed to patch into drm-misc-fixes. > > Best regards > Thomas > > Am 03.04.24 um 11:02 schrieb Jammy Huang: > > There is a while-loop in ast_dp_set_on_off() that could lead to > > infinite-loop. This is because the register, VGACRI-Dx, checked in > > this API is a scratch register actually controlled by a MCU, named > > DPMCU, in BMC. > > > > These scratch registers are protected by scu-lock. If suc-lock is not > > off, DPMCU can not update these registers and then host will have soft > > lockup due to never updated status. > > > > DPMCU is used to control DP and relative registers to handshake with > > host's VGA driver. Even the most time-consuming task, DP's link > > training, is less than 100ms. 200ms should be enough. > > > > Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> > > Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> > > --- > > drivers/gpu/drm/ast/ast_dp.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/gpu/drm/ast/ast_dp.c > > b/drivers/gpu/drm/ast/ast_dp.c index ebb6d8ebd44e..1e9259416980 100644 > > --- a/drivers/gpu/drm/ast/ast_dp.c > > +++ b/drivers/gpu/drm/ast/ast_dp.c > > @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool > on) > > { > > struct ast_device *ast = to_ast_device(dev); > > u8 video_on_off = on; > > + u32 i = 0; > > > > // Video On/Off > > ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) > > ~AST_DP_VIDEO_ENABLE, on); @@ -192,6 +193,8 @@ void > ast_dp_set_on_off(struct drm_device *dev, bool on) > > ASTDP_MIRROR_VIDEO_ENABLE) != > video_on_off) { > > // wait 1 ms > > mdelay(1); > > + if (++i > 200) > > + break; > > } > > } > > } > > > > base-commit: b0546776ad3f332e215cebc0b063ba4351971cca > > -- > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Frankenstrasse 146, 90461 Nuernberg, Germany > GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB > 36809 (AG Nuernberg)
diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c index ebb6d8ebd44e..1e9259416980 100644 --- a/drivers/gpu/drm/ast/ast_dp.c +++ b/drivers/gpu/drm/ast/ast_dp.c @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) { struct ast_device *ast = to_ast_device(dev); u8 video_on_off = on; + u32 i = 0; // Video On/Off ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on); @@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) { // wait 1 ms mdelay(1); + if (++i > 200) + break; } } }